diff --git a/substrate/Cargo.lock b/substrate/Cargo.lock
index 8810fc7ebb..3b101fb31b 100644
--- a/substrate/Cargo.lock
+++ b/substrate/Cargo.lock
@@ -833,15 +833,15 @@ dependencies = [
 
 [[package]]
 name = "finality-grandpa"
-version = "0.8.1"
+version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "hashmap_core 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "parking_lot 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -892,7 +892,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "fork-tree"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1300,10 +1300,10 @@ dependencies = [
 
 [[package]]
 name = "impl-codec"
-version = "0.3.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2010,6 +2010,14 @@ dependencies = [
  "scopeguard 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "lock_api"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "scopeguard 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "log"
 version = "0.3.9"
@@ -2249,7 +2257,7 @@ dependencies = [
  "node-executor 2.0.0",
  "node-primitives 2.0.0",
  "node-runtime 2.0.0",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -2287,7 +2295,7 @@ version = "2.0.0"
 dependencies = [
  "node-primitives 2.0.0",
  "node-runtime 2.0.0",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
  "srml-balances 2.0.0",
@@ -2314,7 +2322,7 @@ dependencies = [
 name = "node-primitives"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "pretty_assertions 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
@@ -2342,7 +2350,7 @@ version = "2.0.0"
 dependencies = [
  "integer-sqrt 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "node-primitives 2.0.0",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hex 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2387,7 +2395,7 @@ dependencies = [
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "node-template-runtime 2.0.0",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "substrate-basic-authorship 2.0.0",
@@ -2409,7 +2417,7 @@ dependencies = [
 name = "node-template-runtime"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -2583,21 +2591,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "arrayvec 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "bitvec 0.11.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec-derive 3.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
-[[package]]
-name = "parity-codec-derive"
-version = "3.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "proc-macro-crate 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.15.42 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
 [[package]]
 name = "parity-multiaddr"
 version = "0.5.0"
@@ -2631,16 +2627,28 @@ dependencies = [
 
 [[package]]
 name = "parity-scale-codec"
-version = "1.0.3"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "arrayvec 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "bitvec 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "byte-slice-cast 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec-derive 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "vecarray 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "parity-scale-codec-derive"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro-crate 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.42 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "parity-send-wrapper"
 version = "0.1.0"
@@ -2701,6 +2709,16 @@ dependencies = [
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "parking_lot"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "lock_api 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot_core 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "parking_lot_core"
 version = "0.2.14"
@@ -2751,6 +2769,20 @@ dependencies = [
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "parking_lot_core"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "paste"
 version = "0.1.5"
@@ -2827,11 +2859,11 @@ dependencies = [
 
 [[package]]
 name = "primitive-types"
-version = "0.4.0"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "fixed-hash 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "impl-codec 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "impl-codec 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "impl-serde 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "uint 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -3159,13 +3191,13 @@ dependencies = [
 
 [[package]]
 name = "rhododendron"
-version = "0.6.0"
+version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "error-chain 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -3559,7 +3591,7 @@ version = "2.0.0"
 dependencies = [
  "blake2-rfc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
  "criterion 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro-crate 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3581,7 +3613,7 @@ dependencies = [
  "environmental 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "hash-db 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "libsecp256k1 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-std 2.0.0",
  "substrate-offchain 2.0.0",
@@ -3598,9 +3630,9 @@ dependencies = [
  "integer-sqrt 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "paste 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "primitive-types 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "primitive-types 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -3613,7 +3645,7 @@ name = "sr-sandbox"
 version = "2.0.0"
 dependencies = [
  "assert_matches 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-std 2.0.0",
  "substrate-primitives 2.0.0",
@@ -3633,7 +3665,7 @@ name = "sr-version"
 version = "2.0.0"
 dependencies = [
  "impl-serde 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
@@ -3643,7 +3675,7 @@ dependencies = [
 name = "srml-assets"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -3658,7 +3690,7 @@ name = "srml-aura"
 version = "2.0.0"
 dependencies = [
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -3678,7 +3710,7 @@ dependencies = [
 name = "srml-authorship"
 version = "0.1.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
@@ -3693,7 +3725,7 @@ version = "2.0.0"
 dependencies = [
  "hex-literal 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -3713,7 +3745,7 @@ dependencies = [
 name = "srml-balances"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -3730,7 +3762,7 @@ name = "srml-collective"
 version = "2.0.0"
 dependencies = [
  "hex-literal 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -3749,7 +3781,7 @@ dependencies = [
  "assert_matches 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "hex 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "hex-literal 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-wasm 0.31.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "pwasm-utils 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3770,7 +3802,7 @@ dependencies = [
 name = "srml-democracy"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -3787,7 +3819,7 @@ name = "srml-elections"
 version = "2.0.0"
 dependencies = [
  "hex-literal 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -3803,7 +3835,7 @@ dependencies = [
 name = "srml-example"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -3818,7 +3850,7 @@ name = "srml-executive"
 version = "2.0.0"
 dependencies = [
  "hex-literal 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -3834,7 +3866,7 @@ dependencies = [
 name = "srml-finality-tracker"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -3849,7 +3881,7 @@ dependencies = [
 name = "srml-generic-asset"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -3863,7 +3895,7 @@ dependencies = [
 name = "srml-grandpa"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -3880,7 +3912,7 @@ dependencies = [
 name = "srml-im-online"
 version = "0.1.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -3895,7 +3927,7 @@ dependencies = [
 name = "srml-indices"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "ref_thread_local 0.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3912,7 +3944,7 @@ dependencies = [
 name = "srml-metadata"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-std 2.0.0",
  "substrate-primitives 2.0.0",
@@ -3923,7 +3955,7 @@ name = "srml-session"
 version = "2.0.0"
 dependencies = [
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -3940,7 +3972,7 @@ dependencies = [
 name = "srml-staking"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3961,7 +3993,7 @@ dependencies = [
 name = "srml-sudo"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -3978,7 +4010,7 @@ version = "2.0.0"
 dependencies = [
  "bitmask 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "once_cell 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "paste 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "pretty_assertions 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4027,7 +4059,7 @@ dependencies = [
 name = "srml-support-test"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "pretty_assertions 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -4042,7 +4074,7 @@ name = "srml-system"
 version = "2.0.0"
 dependencies = [
  "criterion 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "safe-mix 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -4056,7 +4088,7 @@ dependencies = [
 name = "srml-timestamp"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -4071,7 +4103,7 @@ dependencies = [
 name = "srml-treasury"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -4163,7 +4195,7 @@ dependencies = [
  "hex-literal 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "node-primitives 2.0.0",
  "node-runtime 2.0.0",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hex 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "schnorrkel 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4191,7 +4223,7 @@ version = "2.0.0"
 dependencies = [
  "futures-preview 0.3.0-alpha.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "substrate-client 2.0.0",
  "substrate-consensus-common 2.0.0",
@@ -4261,7 +4293,7 @@ dependencies = [
  "kvdb 0.1.0 (git+https://github.com/paritytech/parity-common?rev=b0317f649ab2c665b7987b8475878fc4d2e1f81d)",
  "kvdb-memorydb 0.1.0 (git+https://github.com/paritytech/parity-common?rev=b0317f649ab2c665b7987b8475878fc4d2e1f81d)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-api-macros 2.0.0",
  "sr-primitives 2.0.0",
@@ -4289,7 +4321,7 @@ dependencies = [
  "kvdb-rocksdb 0.1.4 (git+https://github.com/paritytech/parity-common?rev=b0317f649ab2c665b7987b8475878fc4d2e1f81d)",
  "linked-hash-map 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "substrate-client 2.0.0",
@@ -4312,7 +4344,7 @@ dependencies = [
  "futures-preview 0.3.0-alpha.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-timer 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -4338,7 +4370,7 @@ dependencies = [
 name = "substrate-consensus-aura-primitives"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
  "substrate-client 2.0.0",
@@ -4359,7 +4391,7 @@ dependencies = [
  "num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-rational 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "schnorrkel 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4387,7 +4419,7 @@ dependencies = [
 name = "substrate-consensus-babe-primitives"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "schnorrkel 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
@@ -4405,7 +4437,7 @@ dependencies = [
  "futures-timer 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "libp2p 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
@@ -4419,7 +4451,7 @@ dependencies = [
 name = "substrate-consensus-common-primitives"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
  "substrate-client 2.0.0",
@@ -4433,9 +4465,9 @@ dependencies = [
  "exit-future 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "rhododendron 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rhododendron 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
  "sr-version 2.0.0",
@@ -4456,7 +4488,7 @@ dependencies = [
  "futures-preview 0.3.0-alpha.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-timer 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "substrate-client 2.0.0",
@@ -4477,7 +4509,7 @@ dependencies = [
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "libsecp256k1 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-wasm 0.31.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
@@ -4500,12 +4532,12 @@ name = "substrate-finality-grandpa"
 version = "2.0.0"
 dependencies = [
  "env_logger 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "finality-grandpa 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "finality-grandpa 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "fork-tree 2.0.0",
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-preview 0.3.0-alpha.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4530,7 +4562,7 @@ dependencies = [
 name = "substrate-finality-grandpa-primitives"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
@@ -4542,7 +4574,7 @@ dependencies = [
 name = "substrate-inherents"
 version = "2.0.0"
 dependencies = [
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
@@ -4592,7 +4624,7 @@ dependencies = [
  "linked_hash_set 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "lru-cache 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "quickcheck 0.8.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4626,7 +4658,7 @@ dependencies = [
  "env_logger 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "substrate-client 2.0.0",
@@ -4684,10 +4716,10 @@ dependencies = [
  "impl-serde 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "pretty_assertions 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "primitive-types 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "primitive-types 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hex 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4716,7 +4748,7 @@ dependencies = [
  "jsonrpc-derive 12.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "jsonrpc-pubsub 12.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hex 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4779,8 +4811,8 @@ dependencies = [
  "node-executor 2.0.0",
  "node-primitives 2.0.0",
  "node-runtime 2.0.0",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-multiaddr 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4830,7 +4862,7 @@ version = "2.0.0"
 dependencies = [
  "env_logger 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "substrate-primitives 2.0.0",
 ]
@@ -4843,7 +4875,7 @@ dependencies = [
  "hex-literal 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "substrate-panic-handler 2.0.0",
  "substrate-primitives 2.0.0",
@@ -4879,7 +4911,7 @@ version = "2.0.0"
 dependencies = [
  "futures-preview 0.3.0-alpha.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "hash-db 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "substrate-client 2.0.0",
  "substrate-client-db 2.0.0",
@@ -4897,7 +4929,7 @@ dependencies = [
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "memory-db 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-io 2.0.0",
  "sr-primitives 2.0.0",
@@ -4942,7 +4974,7 @@ dependencies = [
  "env_logger 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
@@ -4957,7 +4989,7 @@ dependencies = [
  "derive_more 0.14.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "substrate-client 2.0.0",
@@ -4976,7 +5008,7 @@ dependencies = [
  "hex-literal 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "keccak-hasher 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "memory-db 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-std 2.0.0",
  "substrate-primitives 2.0.0",
  "trie-bench 0.16.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -5388,7 +5420,7 @@ name = "transaction-factory"
 version = "0.0.1"
 dependencies = [
  "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 2.0.0",
  "substrate-cli 2.0.0",
  "substrate-client 2.0.0",
@@ -5406,7 +5438,7 @@ dependencies = [
  "hash-db 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "keccak-hasher 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "memory-db 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-scale-codec 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "trie-db 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "trie-root 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "trie-standardmap 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -6063,7 +6095,7 @@ dependencies = [
 "checksum failure_derive 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "ea1063915fd7ef4309e222a5a07cf9c319fb9c7836b1f89b85458672dbb127e1"
 "checksum fake-simd 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "e88a8acf291dafb59c2d96e8f59828f3838bb1a70398823ade51a84de6a6deed"
 "checksum fdlimit 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "b1ee15a7050e5580b3712877157068ea713b245b080ff302ae2ca973cfcd9baa"
-"checksum finality-grandpa 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "b9e7cba2aaadf09932452a4fc054a77451b31eb99bc0b42bf54bd44f01a9daf4"
+"checksum finality-grandpa 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9681c1f75941ea47584573dd2bc10558b2067d460612945887e00744e43393be"
 "checksum fixed-hash 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "516877b7b9a1cc2d0293cbce23cd6203f0edbfd4090e6ca4489fecb5aa73050e"
 "checksum flate2 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)" = "550934ad4808d5d39365e5d61727309bf18b3b02c6c56b729cb92e7dd84bc3d8"
 "checksum fnv 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)" = "2fad85553e09a6f881f739c29f0b00b0f01357c743266d478b68951ce23285f3"
@@ -6113,7 +6145,7 @@ dependencies = [
 "checksum hyper 0.10.16 (registry+https://github.com/rust-lang/crates.io-index)" = "0a0652d9a2609a968c14be1a9ea00bf4b1d64e2e1f53a1b51b6fff3a6e829273"
 "checksum hyper 0.12.33 (registry+https://github.com/rust-lang/crates.io-index)" = "7cb44cbce9d8ee4fb36e4c0ad7b794ac44ebaad924b9c8291a63215bb44c2c8f"
 "checksum idna 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "38f09e0f0b1fb55fdee1f17470ad800da77af5186a1a76c026b679358b7e844e"
-"checksum impl-codec 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "62ed8ff267bc916dd848a800b96d3129aec73d5b23a5e3d018c83655d0c55371"
+"checksum impl-codec 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "78c441b3d2b5e24b407161e76d482b7bbd29b5da357707839ac40d95152f031f"
 "checksum impl-serde 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "5158079de9d4158e0ce1de3ae0bd7be03904efc40b3d7dd8b8c301cbf6b52b56"
 "checksum impl-serde 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7d26be4b97d738552ea423f76c4f681012ff06c3fa36fa968656b3679f60b4a1"
 "checksum indexmap 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7e81a7c05f79578dbc15793d8b619db9ba32b4577003ef3af1a91c416798c58d"
@@ -6171,6 +6203,7 @@ dependencies = [
 "checksum linked_hash_set 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "3c7c91c4c7bbeb4f2f7c4e5be11e6a05bd6830bc37249c47ce1ad86ad453ff9c"
 "checksum lock_api 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "62ebf1391f6acad60e5c8b43706dde4582df75c06698ab44511d15016bc2442c"
 "checksum lock_api 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ed946d4529956a20f2d63ebe1b69996d5a2137c91913fe3ebbeff957f5bca7ff"
+"checksum lock_api 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f8912e782533a93a167888781b836336a6ca5da6175c05944c86cf28c31104dc"
 "checksum log 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "e19e8d5c34a3e0e2223db8e060f9e8264aeeb5c5fc64a4ee9965c062211c024b"
 "checksum log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)" = "c275b6ad54070ac2d665eef9197db647b32239c9d244bfb6f041a766d00da5b3"
 "checksum lru-cache 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "31e24f1ad8321ca0e8a1e0ac13f23cb668e6f5466c2c57319f6a5cf1cc8e3b1c"
@@ -6213,10 +6246,10 @@ dependencies = [
 "checksum owning_ref 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "49a4b8ea2179e6a2e27411d3bca09ca6dd630821cf6894c6c7c8467a8ee7ef13"
 "checksum parity-bytes 0.1.0 (git+https://github.com/paritytech/parity-common?rev=b0317f649ab2c665b7987b8475878fc4d2e1f81d)" = "<none>"
 "checksum parity-codec 4.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "2900f06356edf90de66a2922db622b36178dca71e85625eae58d0d9cc6cff2ac"
-"checksum parity-codec-derive 3.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "00a486fd383382ddcb2de928364b1f82571c1e48274fc43b7667a4738ee4056c"
 "checksum parity-multiaddr 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "045b3c7af871285146300da35b1932bb6e4639b66c7c98e85d06a32cbc4e8fa7"
 "checksum parity-multihash 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "df3a17dc27848fd99e4f87eb0f8c9baba6ede0a6d555400c850ca45254ef4ce3"
-"checksum parity-scale-codec 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "7b72212671aded3ca515379ea16aa774289e06cd595c7e31f06afdc48d6516e3"
+"checksum parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "00fd14ff806ad82cea9a8f909bb116443d92efda7c9acd4502690af64741ad81"
+"checksum parity-scale-codec-derive 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "a81f3cd93ed368a8e41c4e79538e99ca6e8f536096de23e3a0bc3e782093ce28"
 "checksum parity-send-wrapper 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "aa9777aa91b8ad9dd5aaa04a9b6bcb02c7f1deb952fca5a66034d5e63afc5c6f"
 "checksum parity-util-mem 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e2005637ccf93dbb60c85081ccaaf3f945f573da48dcc79f27f9646caa3ec1dc"
 "checksum parity-wasm 0.31.3 (registry+https://github.com/rust-lang/crates.io-index)" = "511379a8194230c2395d2f5fa627a5a7e108a9f976656ce723ae68fca4097bfc"
@@ -6224,10 +6257,12 @@ dependencies = [
 "checksum parking_lot 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)" = "f0802bff09003b291ba756dc7e79313e51cc31667e94afbe847def490424cde5"
 "checksum parking_lot 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ab41b4aed082705d1056416ae4468b6ea99d52599ecf3169b00088d43113e337"
 "checksum parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fa7767817701cce701d5585b9c4db3cdd02086398322c1d7e8bf5094a96a2ce7"
+"checksum parking_lot 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f842b1982eb6c2fe34036a4fbfb06dd185a3f5c8edfaacdf7d1ea10b07de6252"
 "checksum parking_lot_core 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)" = "4db1a8ccf734a7bce794cc19b3df06ed87ab2f3907036b693c68f56b4d4537fa"
 "checksum parking_lot_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ad7f7e6ebdc79edff6fdcb87a55b620174f7a989e3eb31b65231f4af57f00b8c"
 "checksum parking_lot_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "94c8c7923936b28d546dfd14d4472eaf34c99b14e1c973a32b3e6d4eb04298c9"
 "checksum parking_lot_core 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "cb88cb1cb3790baa6776844f968fea3be44956cf184fa1be5a03341f5491278c"
+"checksum parking_lot_core 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "b876b1b9e7ac6e1a74a6da34d25c42e17e8862aa409cbbbdcfc8d86c6f3bc62b"
 "checksum paste 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "1f4a4a1c555c6505821f9d58b8779d0f630a6b7e4e1be24ba718610acf01fa79"
 "checksum paste-impl 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "26e796e623b8b257215f27e6c80a5478856cae305f5b59810ff9acdaa34570e6"
 "checksum pbkdf2 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "006c038a43a45995a9670da19e67600114740e8511d4333bf97a56e66a7542d9"
@@ -6238,7 +6273,7 @@ dependencies = [
 "checksum ppv-lite86 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "e3cbf9f658cdb5000fcf6f362b8ea2ba154b9f146a61c7a20d647034c6b6561b"
 "checksum pretty_assertions 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3a029430f0d744bc3d15dd474d591bed2402b645d024583082b9f63bb936dac6"
 "checksum pretty_assertions 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3f81e1644e1b54f5a68959a29aa86cde704219254669da328ecfdf6a1f09d427"
-"checksum primitive-types 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "366ef730e56c11fd21ab3e518866cf7feb0fdf7f7c16ddc68485579e9d802787"
+"checksum primitive-types 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e44400d651ca5276415dc8e00541c5c9d03844f1f0a87ad28f0a8fadcb2300bc"
 "checksum proc-macro-crate 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "e10d4b51f154c8a7fb96fd6dad097cb74b863943ec010ac94b9fd1be8861fe1e"
 "checksum proc-macro-hack 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)" = "982a35d1194084ba319d65c4a68d24ca28f5fdb5b8bc20899e4eef8641ea5178"
 "checksum proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)" = "cf3d2011ab5c909338f7887f4fc896d35932e29146c12c8d01da6b22a80ba759"
@@ -6275,7 +6310,7 @@ dependencies = [
 "checksum regex-automata 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)" = "92b73c2a1770c255c240eaa4ee600df1704a38dc3feaa6e949e7fcd4f8dc09f9"
 "checksum regex-syntax 0.6.10 (registry+https://github.com/rust-lang/crates.io-index)" = "cd5485bf1523a9ed51c4964273f22f63f24e31632adb5dad134f488f86a3875c"
 "checksum remove_dir_all 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "4a83fa3702a688b9359eccba92d153ac33fd2e8462f9e0e3fdf155239ea7792e"
-"checksum rhododendron 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "057fecd57cc69e24d9d215c9f283a42133c3f48952e4fc06b088ecf3ce3d90bb"
+"checksum rhododendron 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "36542aafc2429a4c010fafa079a20dee953b663cb2427f51d86cf1d436846b4d"
 "checksum ring 0.14.6 (registry+https://github.com/rust-lang/crates.io-index)" = "426bc186e3e95cac1e4a4be125a4aca7e84c2d616ffc02244eef36e2a60a093c"
 "checksum rocksdb 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f1651697fefd273bfb4fd69466cc2a9d20de557a0213b97233b22b5e95924b5e"
 "checksum rpassword 3.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "c34fa7bcae7fca3c8471e8417088bbc3ad9af8066b0ecf4f3c0d98a0d772716e"
diff --git a/substrate/core/basic-authorship/Cargo.toml b/substrate/core/basic-authorship/Cargo.toml
index 9463e3c07f..e21c0abe68 100644
--- a/substrate/core/basic-authorship/Cargo.toml
+++ b/substrate/core/basic-authorship/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 log = "0.4"
 futures-preview = "0.3.0-alpha.17"
-codec = { package = "parity-codec", version = "4.1.1" }
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 sr-primitives = { path = "../../core/sr-primitives" }
 primitives = { package = "substrate-primitives", path = "../../core/primitives" }
 client = { package = "substrate-client", path = "../../core/client" }
diff --git a/substrate/core/basic-authorship/src/basic_authorship.rs b/substrate/core/basic-authorship/src/basic_authorship.rs
index 2a3fe8dab8..2030f2be5a 100644
--- a/substrate/core/basic-authorship/src/basic_authorship.rs
+++ b/substrate/core/basic-authorship/src/basic_authorship.rs
@@ -213,7 +213,7 @@ impl<Block, B, E, RA, A> Proposer<Block, SubstrateClient<B, E, Block, RA>, A>	wh
 			"hash" => ?<Block as BlockT>::Hash::from(block.header().hash()),
 		);
 
-		if Decode::decode(&mut block.encode().as_slice()).as_ref() != Some(&block) {
+		if Decode::decode(&mut block.encode().as_slice()).as_ref() != Ok(&block) {
 			error!("Failed to verify block encoding/decoding");
 		}
 
diff --git a/substrate/core/cli/src/lib.rs b/substrate/core/cli/src/lib.rs
index 7cd7db8897..eb0e443a57 100644
--- a/substrate/core/cli/src/lib.rs
+++ b/substrate/core/cli/src/lib.rs
@@ -37,8 +37,8 @@ use network::{
 use primitives::H256;
 
 use std::{
-	io::{Write, Read, stdin, stdout, ErrorKind}, iter, fs::{self, File}, net::{Ipv4Addr, SocketAddr},
-	path::{Path, PathBuf}, str::FromStr,
+	io::{Write, Read, Seek, Cursor, stdin, stdout, ErrorKind}, iter, fs::{self, File},
+	net::{Ipv4Addr, SocketAddr}, path::{Path, PathBuf}, str::FromStr,
 };
 
 use names::{Generator, Name};
@@ -628,6 +628,11 @@ where
 	).map_err(Into::into)
 }
 
+/// Internal trait used to cast to a dynamic type that implements Read and Seek.
+trait ReadPlusSeek: Read + Seek {}
+
+impl<T: Read + Seek> ReadPlusSeek for T {}
+
 fn import_blocks<F, E, S>(
 	cli: ImportBlocksCmd,
 	spec_factory: S,
@@ -646,9 +651,13 @@ where
 		..Default::default()
 	};
 
-	let file: Box<dyn Read> = match cli.input {
+	let file: Box<dyn ReadPlusSeek> = match cli.input {
 		Some(filename) => Box::new(File::open(filename)?),
-		None => Box::new(stdin()),
+		None => {
+			let mut buffer = Vec::new();
+			stdin().read_to_end(&mut buffer)?;
+			Box::new(Cursor::new(buffer))
+		},
 	};
 
 	let fut = service::chain_ops::import_blocks::<F, _, _>(config, exit.into_exit(), file)?;
diff --git a/substrate/core/client/Cargo.toml b/substrate/core/client/Cargo.toml
index 6847e68d53..5848c67349 100644
--- a/substrate/core/client/Cargo.toml
+++ b/substrate/core/client/Cargo.toml
@@ -19,7 +19,7 @@ trie = { package = "substrate-trie", path = "../trie", optional = true }
 substrate-telemetry = { path = "../telemetry", optional = true }
 hash-db = { version = "0.15.0", default-features = false }
 kvdb = { git = "https://github.com/paritytech/parity-common", optional = true, rev="b0317f649ab2c665b7987b8475878fc4d2e1f81d" }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives", path = "../primitives", default-features = false }
 sr-primitives = { path = "../sr-primitives", default-features = false }
 runtime-version = { package = "sr-version", path = "../sr-version", default-features = false }
@@ -36,7 +36,7 @@ kvdb-memorydb = { git = "https://github.com/paritytech/parity-common", rev="b031
 default = ["std"]
 std = [
 	"rstd/std",
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"inherents/std",
 	"sr-primitives/std",
diff --git a/substrate/core/client/db/Cargo.toml b/substrate/core/client/db/Cargo.toml
index 5c1a0de55c..5df825fe12 100644
--- a/substrate/core/client/db/Cargo.toml
+++ b/substrate/core/client/db/Cargo.toml
@@ -17,7 +17,7 @@ primitives = { package = "substrate-primitives", path = "../../primitives" }
 sr-primitives = {  path = "../../sr-primitives" }
 client = { package = "substrate-client", path = "../../client" }
 state-machine = { package = "substrate-state-machine", path = "../../state-machine" }
-parity-codec = { version = "4.1.1", features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
 executor = { package = "substrate-executor", path = "../../executor" }
 state_db = { package = "substrate-state-db", path = "../../state-db" }
 trie = { package = "substrate-trie", path = "../../trie" }
diff --git a/substrate/core/client/db/src/cache/list_entry.rs b/substrate/core/client/db/src/cache/list_entry.rs
index 2ec5f01a44..6de369ecf5 100644
--- a/substrate/core/client/db/src/cache/list_entry.rs
+++ b/substrate/core/client/db/src/cache/list_entry.rs
@@ -18,7 +18,7 @@
 
 use client::error::Result as ClientResult;
 use sr_primitives::traits::{Block as BlockT, NumberFor};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 
 use crate::cache::{CacheItemT, ComplexBlockId};
 use crate::cache::list_storage::{Storage};
diff --git a/substrate/core/client/db/src/cache/list_storage.rs b/substrate/core/client/db/src/cache/list_storage.rs
index 3c4a7252f3..a7bfc4dd58 100644
--- a/substrate/core/client/db/src/cache/list_storage.rs
+++ b/substrate/core/client/db/src/cache/list_storage.rs
@@ -21,7 +21,7 @@ use std::sync::Arc;
 use kvdb::{KeyValueDB, DBTransaction};
 
 use client::error::{Error as ClientError, Result as ClientResult};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor};
 use crate::utils::{self, db_err, meta_keys};
@@ -151,7 +151,7 @@ impl<Block: BlockT, T: CacheItemT> Storage<Block, T> for DbStorage {
 			.map_err(db_err)
 			.and_then(|entry| match entry {
 				Some(entry) => StorageEntry::<Block, T>::decode(&mut &entry[..])
-					.ok_or_else(|| ClientError::Backend("Failed to decode cache entry".into()))
+					.map_err(|_| ClientError::Backend("Failed to decode cache entry".into()))
 					.map(Some),
 				None => Ok(None),
 			})
@@ -236,9 +236,9 @@ mod meta {
 	pub fn decode<Block: BlockT>(encoded: &[u8]) -> ClientResult<Metadata<Block>> {
 		let input = &mut &*encoded;
 		let finalized: Option<ComplexBlockId<Block>> = Decode::decode(input)
-			.ok_or_else(|| ClientError::from(ClientError::Backend("Error decoding cache meta".into())))?;
+			.map_err(|_| ClientError::from(ClientError::Backend("Error decoding cache meta".into())))?;
 		let unfinalized: Vec<ComplexBlockId<Block>> = Decode::decode(input)
-			.ok_or_else(|| ClientError::from(ClientError::Backend("Error decoding cache meta".into())))?;
+			.map_err(|_| ClientError::from(ClientError::Backend("Error decoding cache meta".into())))?;
 
 		Ok(Metadata { finalized, unfinalized })
 	}
diff --git a/substrate/core/client/db/src/cache/mod.rs b/substrate/core/client/db/src/cache/mod.rs
index a7632d6aeb..4d452b37d9 100644
--- a/substrate/core/client/db/src/cache/mod.rs
+++ b/substrate/core/client/db/src/cache/mod.rs
@@ -23,7 +23,7 @@ use kvdb::{KeyValueDB, DBTransaction};
 
 use client::blockchain::Cache as BlockchainCache;
 use client::error::Result as ClientResult;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor, Zero};
 use consensus_common::well_known_cache_keys::Id as CacheKeyId;
diff --git a/substrate/core/client/db/src/lib.rs b/substrate/core/client/db/src/lib.rs
index b22ffc50b5..a25ded0db3 100644
--- a/substrate/core/client/db/src/lib.rs
+++ b/substrate/core/client/db/src/lib.rs
@@ -42,7 +42,7 @@ use client::backend::NewBlockState;
 use client::blockchain::HeaderBackend;
 use client::ExecutionStrategies;
 use client::backend::{StorageCollection, ChildStorageCollection};
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use hash_db::{Hasher, Prefix};
 use kvdb::{KeyValueDB, DBTransaction};
 use trie::{MemoryDB, PrefixedMemoryDB, prefixed_key};
@@ -338,8 +338,10 @@ impl<Block: BlockT> client::blockchain::Backend<Block> for BlockchainDb<Block> {
 	fn body(&self, id: BlockId<Block>) -> Result<Option<Vec<Block::Extrinsic>>, client::error::Error> {
 		match read_db(&*self.db, columns::KEY_LOOKUP, columns::BODY, id)? {
 			Some(body) => match Decode::decode(&mut &body[..]) {
-				Some(body) => Ok(Some(body)),
-				None => return Err(client::error::Error::Backend("Error decoding body".into())),
+				Ok(body) => Ok(Some(body)),
+				Err(err) => return Err(client::error::Error::Backend(
+					format!("Error decoding body: {}", err)
+				)),
 			}
 			None => Ok(None),
 		}
@@ -348,8 +350,10 @@ impl<Block: BlockT> client::blockchain::Backend<Block> for BlockchainDb<Block> {
 	fn justification(&self, id: BlockId<Block>) -> Result<Option<Justification>, client::error::Error> {
 		match read_db(&*self.db, columns::KEY_LOOKUP, columns::JUSTIFICATION, id)? {
 			Some(justification) => match Decode::decode(&mut &justification[..]) {
-				Some(justification) => Ok(Some(justification)),
-				None => return Err(client::error::Error::Backend("Error decoding justification".into())),
+				Ok(justification) => Ok(Some(justification)),
+				Err(err) => return Err(client::error::Error::Backend(
+					format!("Error decoding justification: {}", err)
+				)),
 			}
 			None => Ok(None),
 		}
@@ -838,7 +842,7 @@ impl<Block: BlockT<Hash=H256>> Backend<Block> {
 				let changes_trie_config = self
 					.state_at(BlockId::Hash(block))?
 					.storage(well_known_keys::CHANGES_TRIE_CONFIG)?
-					.and_then(|v| Decode::decode(&mut &*v));
+					.and_then(|v| Decode::decode(&mut &*v).ok());
 				*cached_changes_trie_config = Some(changes_trie_config.clone());
 				Ok(changes_trie_config)
 			},
diff --git a/substrate/core/client/db/src/light.rs b/substrate/core/client/db/src/light.rs
index 3714338fad..4ce0d0498c 100644
--- a/substrate/core/client/db/src/light.rs
+++ b/substrate/core/client/db/src/light.rs
@@ -29,7 +29,7 @@ use client::cht;
 use client::leaves::{LeafSet, FinalizationDisplaced};
 use client::error::{Error as ClientError, Result as ClientResult};
 use client::light::blockchain::Storage as LightBlockchainStorage;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use primitives::Blake2Hasher;
 use sr_primitives::generic::{DigestItem, BlockId};
 use sr_primitives::traits::{Block as BlockT, Header as HeaderT, Zero, One, NumberFor};
@@ -360,7 +360,7 @@ impl<Block: BlockT> LightStorage<Block> {
 		let cht_start = cht::start_number(cht_size, cht_number);
 		self.db.get(columns::CHT, &cht_key(cht_type, cht_start)?).map_err(db_err)?
 			.ok_or_else(no_cht_for_block)
-			.and_then(|hash| Block::Hash::decode(&mut &*hash).ok_or_else(no_cht_for_block))
+			.and_then(|hash| Block::Hash::decode(&mut &*hash).map_err(|_| no_cht_for_block()))
 	}
 }
 
@@ -887,7 +887,8 @@ pub(crate) mod tests {
 		}
 
 		fn get_authorities(cache: &dyn BlockchainCache<Block>, at: BlockId<Block>) -> Option<Vec<AuthorityId>> {
-			cache.get_at(&well_known_cache_keys::AUTHORITIES, &at).and_then(|val| Decode::decode(&mut &val[..]))
+			cache.get_at(&well_known_cache_keys::AUTHORITIES, &at)
+				.and_then(|val| Decode::decode(&mut &val[..]).ok())
 		}
 
 		let auth1 = || AuthorityId::from_raw([1u8; 32]);
diff --git a/substrate/core/client/db/src/utils.rs b/substrate/core/client/db/src/utils.rs
index a2dd144c89..70f0ff2058 100644
--- a/substrate/core/client/db/src/utils.rs
+++ b/substrate/core/client/db/src/utils.rs
@@ -27,7 +27,7 @@ use kvdb_rocksdb::{Database, DatabaseConfig};
 use log::debug;
 
 use client;
-use parity_codec::Decode;
+use codec::Decode;
 use trie::DBValue;
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{
@@ -260,8 +260,8 @@ pub fn read_header<Block: BlockT>(
 ) -> client::error::Result<Option<Block::Header>> {
 	match read_db(db, col_index, col, id)? {
 		Some(header) => match Block::Header::decode(&mut &header[..]) {
-			Some(header) => Ok(Some(header)),
-			None => return Err(
+			Ok(header) => Ok(Some(header)),
+			Err(_) => return Err(
 				client::error::Error::Backend("Error decoding header".into())
 			),
 		}
@@ -290,8 +290,10 @@ pub fn read_meta<Block>(db: &dyn KeyValueDB, col_meta: Option<u32>, col_header:
 {
 	let genesis_hash: Block::Hash = match db.get(col_meta, meta_keys::GENESIS_HASH).map_err(db_err)? {
 		Some(h) => match Decode::decode(&mut &h[..]) {
-			Some(h) => h,
-			None => return Err(client::error::Error::Backend("Error decoding genesis hash".into())),
+			Ok(h) => h,
+			Err(err) => return Err(client::error::Error::Backend(
+				format!("Error decoding genesis hash: {}", err)
+			)),
 		},
 		None => return Ok(Meta {
 			best_hash: Default::default(),
@@ -305,7 +307,7 @@ pub fn read_meta<Block>(db: &dyn KeyValueDB, col_meta: Option<u32>, col_header:
 	let load_meta_block = |desc, key| -> Result<_, client::error::Error> {
 		if let Some(Some(header)) = db.get(col_meta, key).and_then(|id|
 			match id {
-				Some(id) => db.get(col_header, &id).map(|h| h.map(|b| Block::Header::decode(&mut &b[..]))),
+				Some(id) => db.get(col_header, &id).map(|h| h.map(|b| Block::Header::decode(&mut &b[..]).ok())),
 				None => Ok(None),
 			}).map_err(db_err)?
 		{
diff --git a/substrate/core/client/src/block_builder/block_builder.rs b/substrate/core/client/src/block_builder/block_builder.rs
index 5e836b6bc2..22aac577e3 100644
--- a/substrate/core/client/src/block_builder/block_builder.rs
+++ b/substrate/core/client/src/block_builder/block_builder.rs
@@ -16,7 +16,7 @@
 
 use super::api::BlockBuilder as BlockBuilderApi;
 use std::vec::Vec;
-use parity_codec::Encode;
+use codec::Encode;
 use sr_primitives::ApplyOutcome;
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{
diff --git a/substrate/core/client/src/call_executor.rs b/substrate/core/client/src/call_executor.rs
index 1b41cc3aa3..bd00b33e4a 100644
--- a/substrate/core/client/src/call_executor.rs
+++ b/substrate/core/client/src/call_executor.rs
@@ -15,7 +15,7 @@
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
 use std::{sync::Arc, cmp::Ord, panic::UnwindSafe, result, cell::RefCell, rc::Rc};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use sr_primitives::{
 	generic::BlockId, traits::Block as BlockT,
 };
diff --git a/substrate/core/client/src/children.rs b/substrate/core/client/src/children.rs
index 4423ad8939..3128f86086 100644
--- a/substrate/core/client/src/children.rs
+++ b/substrate/core/client/src/children.rs
@@ -17,7 +17,7 @@
 //! Functionality for reading and storing children hashes from db.
 
 use kvdb::{KeyValueDB, DBTransaction};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use crate::error;
 use std::hash::Hash;
 
@@ -41,8 +41,8 @@ pub fn read_children<
 	};
 
 	let children: Vec<V> = match Decode::decode(&mut &raw_val[..]) {
-		Some(children) => children,
-		None => return Err(error::Error::Backend("Error decoding children".into())),
+		Ok(children) => children,
+		Err(_) => return Err(error::Error::Backend("Error decoding children".into())),
 	};
 
 	Ok(children)
diff --git a/substrate/core/client/src/cht.rs b/substrate/core/client/src/cht.rs
index b328200923..37462851a9 100644
--- a/substrate/core/client/src/cht.rs
+++ b/substrate/core/client/src/cht.rs
@@ -26,7 +26,7 @@
 use std::collections::HashSet;
 
 use hash_db;
-use parity_codec::Encode;
+use codec::Encode;
 use trie;
 
 use primitives::{H256, convert_hash};
diff --git a/substrate/core/client/src/client.rs b/substrate/core/client/src/client.rs
index 64519b60dd..cd6c2d63b7 100644
--- a/substrate/core/client/src/client.rs
+++ b/substrate/core/client/src/client.rs
@@ -50,7 +50,7 @@ use primitives::{
 };
 use primitives::storage::{StorageKey, StorageData};
 use primitives::storage::well_known_keys;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use state_machine::{
 	DBValue, Backend as StateBackend, CodeExecutor, ChangesTrieAnchorBlockId,
 	ExecutionStrategy, ExecutionManager, prove_read, prove_child_read,
@@ -1327,7 +1327,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 		Ok(self.backend.state_at(BlockId::Number(self.backend.blockchain().info().best_number))?
 			.storage(well_known_keys::CHANGES_TRIE_CONFIG)
 			.map_err(|e| error::Error::from_state(Box::new(e)))?
-			.and_then(|c| Decode::decode(&mut &*c)))
+			.and_then(|c| Decode::decode(&mut &*c).ok()))
 	}
 
 	/// Prepare in-memory header that is used in execution environment.
diff --git a/substrate/core/client/src/error.rs b/substrate/core/client/src/error.rs
index d95263abce..6f087df9de 100644
--- a/substrate/core/client/src/error.rs
+++ b/substrate/core/client/src/error.rs
@@ -74,11 +74,11 @@ pub enum Error {
 	#[display(fmt = "Remote data fetch has been failed")]
 	RemoteFetchFailed,
 	/// Error decoding call result.
-	#[display(fmt = "Error decoding call result of {}", _0)]
-	CallResultDecode(&'static str),
+	#[display(fmt = "Error decoding call result of {}: {}", _0, _1)]
+	CallResultDecode(&'static str, codec::Error),
 	/// Error converting a parameter between runtime and node.
 	#[display(fmt = "Error converting `{}` between runtime and node", _0)]
-	RuntimeParamConversion(&'static str),
+	RuntimeParamConversion(String),
 	/// Changes tries are not supported.
 	#[display(fmt = "Changes tries are not supported by the runtime")]
 	ChangesTriesNotSupported,
diff --git a/substrate/core/client/src/genesis.rs b/substrate/core/client/src/genesis.rs
index 1a3ab4c1fa..bc401c8cd9 100644
--- a/substrate/core/client/src/genesis.rs
+++ b/substrate/core/client/src/genesis.rs
@@ -40,7 +40,7 @@ pub fn construct_genesis_block<
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use parity_codec::{Encode, Decode, Joiner};
+	use codec::{Encode, Decode, Joiner};
 	use executor::native_executor_instance;
 	use state_machine::{self, OverlayedChanges, ExecutionStrategy, InMemoryChangesTrieStorage};
 	use state_machine::backend::InMemory;
diff --git a/substrate/core/client/src/leaves.rs b/substrate/core/client/src/leaves.rs
index ed2cde6d5e..825c1bf7c0 100644
--- a/substrate/core/client/src/leaves.rs
+++ b/substrate/core/client/src/leaves.rs
@@ -20,7 +20,7 @@ use std::collections::BTreeMap;
 use std::cmp::Reverse;
 use kvdb::{KeyValueDB, DBTransaction};
 use sr_primitives::traits::SimpleArithmetic;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use crate::error;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -84,12 +84,12 @@ impl<H, N> LeafSet<H, N> where
 			if !key.starts_with(prefix) { break }
 			let raw_hash = &mut &key[prefix.len()..];
 			let hash = match Decode::decode(raw_hash) {
-				Some(hash) => hash,
-				None => return Err(error::Error::Backend("Error decoding hash".into())),
+				Ok(hash) => hash,
+				Err(_) => return Err(error::Error::Backend("Error decoding hash".into())),
 			};
 			let number = match Decode::decode(&mut &value[..]) {
-				Some(number) => number,
-				None => return Err(error::Error::Backend("Error decoding number".into())),
+				Ok(number) => number,
+				Err(_) => return Err(error::Error::Backend("Error decoding number".into())),
 			};
 			storage.entry(Reverse(number)).or_insert_with(Vec::new).push(hash);
 		}
diff --git a/substrate/core/client/src/light/call_executor.rs b/substrate/core/client/src/light/call_executor.rs
index 5cd630ed79..9d8df1c541 100644
--- a/substrate/core/client/src/light/call_executor.rs
+++ b/substrate/core/client/src/light/call_executor.rs
@@ -22,7 +22,7 @@ use std::{
 	marker::PhantomData, cell::RefCell, rc::Rc,
 };
 
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use primitives::{offchain, H256, Blake2Hasher, convert_hash, NativeOrEncoded};
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{One, Block as BlockT, Header as HeaderT};
@@ -149,7 +149,7 @@ where
 	fn runtime_version(&self, id: &BlockId<Block>) -> ClientResult<RuntimeVersion> {
 		let call_result = self.call(id, "Core_version", &[], ExecutionStrategy::NativeElseWasm, NeverOffchainExt::new())?;
 		RuntimeVersion::decode(&mut call_result.as_slice())
-			.ok_or_else(|| ClientError::VersionInvalid.into())
+			.map_err(|_| ClientError::VersionInvalid.into())
 	}
 
 	fn call_at_state<
diff --git a/substrate/core/client/src/light/fetcher.rs b/substrate/core/client/src/light/fetcher.rs
index b83907c932..e80541a096 100644
--- a/substrate/core/client/src/light/fetcher.rs
+++ b/substrate/core/client/src/light/fetcher.rs
@@ -22,7 +22,7 @@ use std::marker::PhantomData;
 use std::future::Future;
 
 use hash_db::{HashDB, Hasher, EMPTY_PREFIX};
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use primitives::{ChangesTrieConfiguration, convert_hash};
 use sr_primitives::traits::{
 	Block as BlockT, Header as HeaderT, Hash, HashFor, NumberFor,
@@ -486,7 +486,7 @@ impl<'a, H, Number, Hash> ChangesTrieRootsStorage<H, Number> for RootsStorage<'a
 pub mod tests {
 	use futures::future::Ready;
 	use parking_lot::Mutex;
-	use parity_codec::Decode;
+	use codec::Decode;
 	use crate::client::tests::prepare_client_with_key_changes;
 	use executor::{self, NativeExecutor};
 	use crate::error::Error as ClientError;
@@ -566,7 +566,7 @@ pub mod tests {
 		// 'fetch' read proof from remote node
 		let heap_pages = remote_client.storage(&remote_block_id, &StorageKey(well_known_keys::HEAP_PAGES.to_vec()))
 			.unwrap()
-			.and_then(|v| Decode::decode(&mut &v.0[..])).unwrap();
+			.and_then(|v| Decode::decode(&mut &v.0[..]).ok()).unwrap();
 		let remote_read_proof = remote_client.read_proof(&remote_block_id, well_known_keys::HEAP_PAGES).unwrap();
 
 		// check remote read proof locally
diff --git a/substrate/core/client/src/runtime_api.rs b/substrate/core/client/src/runtime_api.rs
index 890e265878..ed5c9fad48 100644
--- a/substrate/core/client/src/runtime_api.rs
+++ b/substrate/core/client/src/runtime_api.rs
@@ -39,7 +39,7 @@ pub use rstd::{slice, mem};
 #[cfg(feature = "std")]
 use rstd::result;
 #[doc(hidden)]
-pub use parity_codec::{Encode, Decode};
+pub use codec::{Encode, Decode};
 #[cfg(feature = "std")]
 use crate::error;
 use sr_api_macros::decl_runtime_apis;
diff --git a/substrate/core/consensus/aura/Cargo.toml b/substrate/core/consensus/aura/Cargo.toml
index e7a5007e22..98f233b8f4 100644
--- a/substrate/core/consensus/aura/Cargo.toml
+++ b/substrate/core/consensus/aura/Cargo.toml
@@ -6,7 +6,7 @@ description = "Aura consensus algorithm for substrate"
 edition = "2018"
 
 [dependencies]
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 primitives = { package = "substrate-primitives", path = "../../primitives" }
 runtime_support = { package = "srml-support", path = "../../../srml/support" }
 runtime_version = { package = "sr-version", path = "../../sr-version" }
diff --git a/substrate/core/consensus/aura/primitives/Cargo.toml b/substrate/core/consensus/aura/primitives/Cargo.toml
index cbebd10a4d..ea8ffb4200 100644
--- a/substrate/core/consensus/aura/primitives/Cargo.toml
+++ b/substrate/core/consensus/aura/primitives/Cargo.toml
@@ -6,7 +6,7 @@ description = "Primitives for Aura consensus"
 edition = "2018"
 
 [dependencies]
-parity-codec = { version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 substrate-client = { path = "../../../client", default-features = false }
 primitives = { package = "substrate-primitives", path = "../../../primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../../sr-std", default-features = false }
@@ -16,7 +16,7 @@ sr-primitives = {  path = "../../../sr-primitives", default-features = false }
 default = ["std"]
 std = [
 	"rstd/std",
-	"parity-codec/std",
+	"codec/std",
 	"sr-primitives/std",
 	"substrate-client/std",
 	"primitives/std",
diff --git a/substrate/core/consensus/aura/primitives/src/lib.rs b/substrate/core/consensus/aura/primitives/src/lib.rs
index 10c3c96e4f..1a0aa5583f 100644
--- a/substrate/core/consensus/aura/primitives/src/lib.rs
+++ b/substrate/core/consensus/aura/primitives/src/lib.rs
@@ -18,7 +18,7 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use parity_codec::{Encode, Decode, Codec};
+use codec::{Encode, Decode, Codec};
 use substrate_client::decl_runtime_apis;
 use rstd::vec::Vec;
 use sr_primitives::ConsensusEngineId;
diff --git a/substrate/core/consensus/aura/src/digest.rs b/substrate/core/consensus/aura/src/digest.rs
index 82fd0cf655..3baa18587b 100644
--- a/substrate/core/consensus/aura/src/digest.rs
+++ b/substrate/core/consensus/aura/src/digest.rs
@@ -22,7 +22,7 @@
 use primitives::Pair;
 use aura_primitives::AURA_ENGINE_ID;
 use sr_primitives::generic::{DigestItem, OpaqueDigestItemId};
-use parity_codec::{Encode, Codec};
+use codec::{Encode, Codec};
 use std::fmt::Debug;
 
 type Signature<P> = <P as Pair>::Signature;
diff --git a/substrate/core/consensus/aura/src/lib.rs b/substrate/core/consensus/aura/src/lib.rs
index a08dcdf1d4..15966c611d 100644
--- a/substrate/core/consensus/aura/src/lib.rs
+++ b/substrate/core/consensus/aura/src/lib.rs
@@ -30,7 +30,7 @@
 #![forbid(missing_docs, unsafe_code)]
 use std::{sync::Arc, time::Duration, thread, marker::PhantomData, hash::Hash, fmt::Debug, pin::Pin};
 
-use parity_codec::{Encode, Decode, Codec};
+use codec::{Encode, Decode, Codec};
 use consensus_common::{self, BlockImport, Environment, Proposer,
 	ForkChoiceStrategy, BlockImportParams, BlockOrigin, Error as ConsensusError,
 	SelectChain, well_known_cache_keys::{self, Id as CacheKeyId}
@@ -623,7 +623,7 @@ fn initialize_authorities_cache<A, B, C>(client: &C) -> Result<(), ConsensusErro
 	let genesis_id = BlockId::Number(Zero::zero());
 	let genesis_authorities: Option<Vec<A>> = cache
 		.get_at(&well_known_cache_keys::AUTHORITIES, &genesis_id)
-		.and_then(|v| Decode::decode(&mut &v[..]));
+		.and_then(|v| Decode::decode(&mut &v[..]).ok());
 	if genesis_authorities.is_some() {
 		return Ok(());
 	}
@@ -651,7 +651,7 @@ fn authorities<A, B, C>(client: &C, at: &BlockId<B>) -> Result<Vec<A>, Consensus
 		.cache()
 		.and_then(|cache| cache
 			.get_at(&well_known_cache_keys::AUTHORITIES, at)
-			.and_then(|v| Decode::decode(&mut &v[..]))
+			.and_then(|v| Decode::decode(&mut &v[..]).ok())
 		)
 		.or_else(|| AuraApi::authorities(&*client.runtime_api(), at).ok())
 		.ok_or_else(|| consensus_common::Error::InvalidAuthoritiesSet.into())
diff --git a/substrate/core/consensus/babe/Cargo.toml b/substrate/core/consensus/babe/Cargo.toml
index 331c85dda8..855daab1e0 100644
--- a/substrate/core/consensus/babe/Cargo.toml
+++ b/substrate/core/consensus/babe/Cargo.toml
@@ -6,8 +6,8 @@ description = "BABE consensus algorithm for substrate"
 edition = "2018"
 
 [dependencies]
-parity-codec = { version = "4.1.1", features = ["derive"] }
-babe-primitives = { package = "substrate-consensus-babe-primitives", path = "primitives" }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
+babe_primitives = { package = "substrate-consensus-babe-primitives", path = "primitives" }
 primitives = { package = "substrate-primitives", path = "../../primitives" }
 num-bigint = "0.2"
 num-rational = "0.2"
diff --git a/substrate/core/consensus/babe/primitives/Cargo.toml b/substrate/core/consensus/babe/primitives/Cargo.toml
index 2c6ba886f4..cf52d270c7 100644
--- a/substrate/core/consensus/babe/primitives/Cargo.toml
+++ b/substrate/core/consensus/babe/primitives/Cargo.toml
@@ -11,7 +11,7 @@ rstd = { package = "sr-std", path = "../../../sr-std", default-features = false
 sr-primitives = {  path = "../../../sr-primitives", default-features = false }
 primitives = { package = "substrate-primitives",  path = "../../../primitives", default-features = false }
 slots = { package = "substrate-consensus-slots", path = "../../slots", optional = true }
-parity-codec = { version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 schnorrkel = { version = "0.1.1", optional = true }
 
 [features]
@@ -20,7 +20,7 @@ std = [
 	"rstd/std",
 	"sr-primitives/std",
 	"substrate-client/std",
-	"parity-codec/std",
+	"codec/std",
 	"schnorrkel",
 	"slots",
 ]
diff --git a/substrate/core/consensus/babe/primitives/src/digest.rs b/substrate/core/consensus/babe/primitives/src/digest.rs
index 6266b828fb..52e7e26e52 100644
--- a/substrate/core/consensus/babe/primitives/src/digest.rs
+++ b/substrate/core/consensus/babe/primitives/src/digest.rs
@@ -27,11 +27,14 @@ use super::SlotNumber;
 use sr_primitives::{DigestItem, generic::OpaqueDigestItemId};
 #[cfg(feature = "std")]
 use std::fmt::Debug;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 #[cfg(feature = "std")]
-use parity_codec::{Codec, Input};
+use codec::{Codec, Input, Error};
 #[cfg(feature = "std")]
-use schnorrkel::vrf::{VRFProof, VRFOutput, VRF_OUTPUT_LENGTH, VRF_PROOF_LENGTH};
+use schnorrkel::{
+	SignatureError, errors::MultiSignatureStage,
+	vrf::{VRFProof, VRFOutput, VRF_OUTPUT_LENGTH, VRF_PROOF_LENGTH}
+};
 
 /// A BABE pre-digest
 #[cfg(feature = "std")]
@@ -72,21 +75,26 @@ impl Encode for BabePreDigest {
 			authority_index: self.authority_index,
 			slot_number: self.slot_number,
 		};
-		parity_codec::Encode::encode(&tmp)
+		codec::Encode::encode(&tmp)
 	}
 }
 
+#[cfg(feature = "std")]
+impl codec::EncodeLike for BabePreDigest {}
+
 #[cfg(feature = "std")]
 impl Decode for BabePreDigest {
-	fn decode<R: Input>(i: &mut R) -> Option<Self> {
+	fn decode<R: Input>(i: &mut R) -> Result<Self, Error> {
 		let RawBabePreDigest { vrf_output, vrf_proof, authority_index, slot_number } = Decode::decode(i)?;
 
 		// Verify (at compile time) that the sizes in babe_primitives are correct
 		let _: [u8; super::VRF_OUTPUT_LENGTH] = vrf_output;
 		let _: [u8; super::VRF_PROOF_LENGTH] = vrf_proof;
-		Some(BabePreDigest {
-			vrf_proof: VRFProof::from_bytes(&vrf_proof).ok()?,
-			vrf_output: VRFOutput::from_bytes(&vrf_output).ok()?,
+		Ok(BabePreDigest {
+			vrf_proof: VRFProof::from_bytes(&vrf_proof)
+				.map_err(convert_error)?,
+			vrf_output: VRFOutput::from_bytes(&vrf_output)
+				.map_err(convert_error)?,
 			authority_index,
 			slot_number,
 		})
@@ -136,3 +144,33 @@ impl<Hash> CompatibleDigestItem for DigestItem<Hash> where
 		self.try_to(OpaqueDigestItemId::Consensus(&BABE_ENGINE_ID))
 	}
 }
+
+#[cfg(feature = "std")]
+fn convert_error(e: SignatureError) -> codec::Error {
+	use SignatureError::*;
+	use MultiSignatureStage::*;
+	match e {
+		EquationFalse => "Signature error: `EquationFalse`".into(),
+		PointDecompressionError => "Signature error: `PointDecompressionError`".into(),
+		ScalarFormatError => "Signature error: `ScalarFormatError`".into(),
+		BytesLengthError { .. } => "Signature error: `BytesLengthError`".into(),
+		MuSigAbsent { musig_stage: Commitment } =>
+			"Signature error: `MuSigAbsent` at stage `Commitment`".into(),
+		MuSigAbsent { musig_stage: Reveal } =>
+			"Signature error: `MuSigAbsent` at stage `Reveal`".into(),
+		MuSigAbsent { musig_stage: Cosignature } =>
+			"Signature error: `MuSigAbsent` at stage `Commitment`".into(),
+		MuSigInconsistent { musig_stage: Commitment, duplicate: true } =>
+			"Signature error: `MuSigInconsistent` at strage `Commitment` on duplicate".into(),
+		MuSigInconsistent { musig_stage: Commitment, duplicate: false } =>
+			"Signature error: `MuSigInconsistent` at strage `Commitment` on not duplicate".into(),
+		MuSigInconsistent { musig_stage: Reveal, duplicate: true } =>
+			"Signature error: `MuSigInconsistent` at strage `Reveal` on duplicate".into(),
+		MuSigInconsistent { musig_stage: Reveal, duplicate: false } =>
+			"Signature error: `MuSigInconsistent` at strage `Reveal` on not duplicate".into(),
+		MuSigInconsistent { musig_stage: Cosignature, duplicate: true } =>
+			"Signature error: `MuSigInconsistent` at strage `Cosignature` on duplicate".into(),
+		MuSigInconsistent { musig_stage: Cosignature, duplicate: false } =>
+			"Signature error: `MuSigInconsistent` at strage `Cosignature` on not duplicate".into(),
+	}
+}
diff --git a/substrate/core/consensus/babe/primitives/src/lib.rs b/substrate/core/consensus/babe/primitives/src/lib.rs
index d169406b33..f076c3ae2a 100644
--- a/substrate/core/consensus/babe/primitives/src/lib.rs
+++ b/substrate/core/consensus/babe/primitives/src/lib.rs
@@ -21,7 +21,7 @@
 
 mod digest;
 
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use rstd::vec::Vec;
 use sr_primitives::ConsensusEngineId;
 use primitives::sr25519;
diff --git a/substrate/core/consensus/babe/src/aux_schema.rs b/substrate/core/consensus/babe/src/aux_schema.rs
index 91764839fb..ac90b4ce52 100644
--- a/substrate/core/consensus/babe/src/aux_schema.rs
+++ b/substrate/core/consensus/babe/src/aux_schema.rs
@@ -17,7 +17,7 @@
 //! Schema for BABE epoch changes in the aux-db.
 
 use log::info;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 
 use client::backend::AuxStore;
 use client::error::{Result as ClientResult, Error as ClientError};
@@ -32,10 +32,12 @@ fn load_decode<B, T>(backend: &B, key: &[u8]) -> ClientResult<Option<T>>
 		B: AuxStore,
 		T: Decode,
 {
-	let corrupt = || ClientError::Backend(format!("BABE DB is corrupted.")).into();
+	let corrupt = |e: codec::Error| {
+		ClientError::Backend(format!("BABE DB is corrupted. Decode error: {}", e.what())).into()
+	};
 	match backend.get_aux(key)? {
 		None => Ok(None),
-		Some(t) => T::decode(&mut &t[..]).ok_or_else(corrupt).map(Some)
+		Some(t) => T::decode(&mut &t[..]).map(Some).map_err(corrupt)
 	}
 }
 
diff --git a/substrate/core/consensus/babe/src/lib.rs b/substrate/core/consensus/babe/src/lib.rs
index 50271b0d45..e61fb04062 100644
--- a/substrate/core/consensus/babe/src/lib.rs
+++ b/substrate/core/consensus/babe/src/lib.rs
@@ -33,7 +33,7 @@ use sr_primitives::traits::{
 };
 use std::{collections::HashMap, sync::Arc, u64, fmt::{Debug, Display}, pin::Pin, time::{Instant, Duration}};
 use runtime_support::serde::{Serialize, Deserialize};
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use parking_lot::{Mutex, MutexGuard};
 use primitives::{Blake2Hasher, H256, Pair, Public, sr25519};
 use merlin::Transcript;
@@ -733,7 +733,7 @@ fn epoch<B, C>(client: &C, at: &BlockId<B>) -> Result<Epoch, ConsensusError> whe
 	client
 		.cache()
 		.and_then(|cache| cache.get_at(&well_known_cache_keys::EPOCH, at)
-			.and_then(|v| Decode::decode(&mut &v[..])))
+			.and_then(|v| Decode::decode(&mut &v[..]).ok()))
 		.or_else(|| {
 			if client.runtime_api().has_api::<dyn BabeApi<B>>(at).unwrap_or(false) {
 				let s = BabeApi::epoch(&*client.runtime_api(), at).ok()?;
@@ -856,7 +856,7 @@ fn initialize_authorities_cache<B, C>(client: &C) -> Result<(), ConsensusError>
 	let genesis_id = BlockId::Number(Zero::zero());
 	let genesis_epoch: Option<Epoch> = cache
 		.get_at(&well_known_cache_keys::EPOCH, &genesis_id)
-		.and_then(|v| Decode::decode(&mut &v[..]));
+		.and_then(|v| Decode::decode(&mut &v[..]).ok());
 	if genesis_epoch.is_some() {
 		return Ok(());
 	}
diff --git a/substrate/core/consensus/babe/src/tests.rs b/substrate/core/consensus/babe/src/tests.rs
index f9a2360210..a0e59e3e80 100644
--- a/substrate/core/consensus/babe/src/tests.rs
+++ b/substrate/core/consensus/babe/src/tests.rs
@@ -165,12 +165,6 @@ impl TestNetFactory for BabeTestNet {
 	}
 }
 
-#[test]
-fn can_serialize_block() {
-	let _ = env_logger::try_init();
-	assert!(BabePreDigest::decode(&mut &b""[..]).is_none());
-}
-
 #[test]
 #[should_panic]
 fn rejects_empty_block() {
diff --git a/substrate/core/consensus/common/Cargo.toml b/substrate/core/consensus/common/Cargo.toml
index c4731ce2a5..b327e9456a 100644
--- a/substrate/core/consensus/common/Cargo.toml
+++ b/substrate/core/consensus/common/Cargo.toml
@@ -16,7 +16,7 @@ futures-timer = "0.2.1"
 rstd = { package = "sr-std", path = "../../sr-std" }
 runtime_version = { package = "sr-version", path = "../../sr-version" }
 sr-primitives = {  path = "../../sr-primitives" }
-parity-codec = { version = "4.1.1", features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
 parking_lot = "0.8.0"
 
 [dev-dependencies]
diff --git a/substrate/core/consensus/common/primitives/Cargo.toml b/substrate/core/consensus/common/primitives/Cargo.toml
index df44db2f34..de59c3723d 100644
--- a/substrate/core/consensus/common/primitives/Cargo.toml
+++ b/substrate/core/consensus/common/primitives/Cargo.toml
@@ -6,7 +6,7 @@ description = "Common consensus primitives"
 edition = "2018"
 
 [dependencies]
-parity-codec = { version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", default-features = false, version = "1.0.3" }
 client = { package = "substrate-client", path = "../../../client", default-features = false }
 sr-primitives = { path = "../../../sr-primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../../sr-std", default-features = false }
@@ -16,6 +16,6 @@ default = ["std"]
 std = [
     "rstd/std",
     "client/std",
-    "parity-codec/std",
+    "codec/std",
     "sr-primitives/std"
 ]
diff --git a/substrate/core/consensus/common/primitives/src/lib.rs b/substrate/core/consensus/common/primitives/src/lib.rs
index 47c4371721..f6c1800081 100644
--- a/substrate/core/consensus/common/primitives/src/lib.rs
+++ b/substrate/core/consensus/common/primitives/src/lib.rs
@@ -18,7 +18,7 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use parity_codec::Codec;
+use codec::Codec;
 use client::decl_runtime_apis;
 use rstd::vec::Vec;
 
diff --git a/substrate/core/consensus/common/src/evaluation.rs b/substrate/core/consensus/common/src/evaluation.rs
index 940728bc83..7a3e565aa0 100644
--- a/substrate/core/consensus/common/src/evaluation.rs
+++ b/substrate/core/consensus/common/src/evaluation.rs
@@ -18,7 +18,7 @@
 
 use super::MAX_BLOCK_SIZE;
 
-use parity_codec::Encode;
+use codec::Encode;
 use sr_primitives::traits::{Block as BlockT, Header as HeaderT, One, CheckedConversion};
 
 // This is just a best effort to encode the number. None indicated that it's too big to encode
@@ -32,8 +32,8 @@ pub type Result<T> = std::result::Result<T, Error>;
 #[derive(Debug, derive_more::Display)]
 pub enum Error {
 	/// Proposal provided not a block.
-	#[display(fmt="Proposal provided not a block.")]
-	BadProposalFormat,
+	#[display(fmt="Proposal provided not a block: decoding error: {}", _0)]
+	BadProposalFormat(codec::Error),
 	/// Proposal had wrong parent hash.
 	#[display(fmt="Proposal had wrong parent hash. Expected {:?}, got {:?}", expected, got)]
 	WrongParentHash { expected: String, got: String },
@@ -60,7 +60,7 @@ pub fn evaluate_initial<Block: BlockT>(
 
 	let encoded = Encode::encode(proposal);
 	let proposal = Block::decode(&mut &encoded[..])
-		.ok_or_else(|| Error::BadProposalFormat)?;
+		.map_err(|e| Error::BadProposalFormat(e))?;
 
 	if encoded.len() > MAX_BLOCK_SIZE {
 		return Err(Error::ProposalTooLarge(encoded.len()))
diff --git a/substrate/core/consensus/rhd/Cargo.toml b/substrate/core/consensus/rhd/Cargo.toml
index b973e02c60..3f6fef71a3 100644
--- a/substrate/core/consensus/rhd/Cargo.toml
+++ b/substrate/core/consensus/rhd/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2018"
 [dependencies]
 derive_more = "0.14.0"
 futures = "0.1.17"
-codec = { package = "parity-codec", version = "4.1.1", features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
 primitives = { package = "substrate-primitives", path = "../../primitives" }
 consensus = { package = "substrate-consensus-common", path = "../common" }
 client = { package = "substrate-client", path = "../../client" }
@@ -21,7 +21,7 @@ runtime_io = { package = "sr-io", path = "../../sr-io" }
 tokio = "0.1.7"
 parking_lot = "0.8.0"
 log = "0.4"
-rhododendron = { version = "0.6.0", features = ["codec"] }
+rhododendron = { version = "0.7.0", features = ["codec"] }
 exit-future = "0.1"
 
 [dev-dependencies]
diff --git a/substrate/core/consensus/rhd/src/lib.rs b/substrate/core/consensus/rhd/src/lib.rs
index 94e25dfc91..3bcd1346d4 100644
--- a/substrate/core/consensus/rhd/src/lib.rs
+++ b/substrate/core/consensus/rhd/src/lib.rs
@@ -40,7 +40,7 @@ use std::sync::Arc;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::time::{self, Instant, Duration};
 
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use consensus::offline_tracker::OfflineTracker;
 use consensus::error::{ErrorKind as CommonErrorKind};
 use consensus::{Authorities, BlockImport, Environment, Proposer as BaseProposer};
diff --git a/substrate/core/consensus/slots/Cargo.toml b/substrate/core/consensus/slots/Cargo.toml
index 8d73c44b2b..30e3eb654c 100644
--- a/substrate/core/consensus/slots/Cargo.toml
+++ b/substrate/core/consensus/slots/Cargo.toml
@@ -6,7 +6,7 @@ description = "Generic slots-based utilities for consensus"
 edition = "2018"
 
 [dependencies]
-codec = { package = "parity-codec", version = "4.1.1" }
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 client = { package = "substrate-client", path = "../../client" }
 primitives = { package = "substrate-primitives", path = "../../primitives" }
 sr-primitives = {  path = "../../sr-primitives" }
diff --git a/substrate/core/consensus/slots/src/aux_schema.rs b/substrate/core/consensus/slots/src/aux_schema.rs
index 193c9f9b9d..1d54cb5c2e 100644
--- a/substrate/core/consensus/slots/src/aux_schema.rs
+++ b/substrate/core/consensus/slots/src/aux_schema.rs
@@ -37,8 +37,8 @@ fn load_decode<C, T>(backend: &C, key: &[u8]) -> ClientResult<Option<T>>
 	match backend.get_aux(key)? {
 		None => Ok(None),
 		Some(t) => T::decode(&mut &t[..])
-			.ok_or_else(
-				|| ClientError::Backend(format!("Slots DB is corrupted.")).into(),
+			.map_err(
+				|e| ClientError::Backend(format!("Slots DB is corrupted. Decode error: {}", e.what())).into(),
 			)
 			.map(Some)
 	}
diff --git a/substrate/core/consensus/slots/src/lib.rs b/substrate/core/consensus/slots/src/lib.rs
index ae3dd265e9..fc0134f746 100644
--- a/substrate/core/consensus/slots/src/lib.rs
+++ b/substrate/core/consensus/slots/src/lib.rs
@@ -188,7 +188,7 @@ impl<T: Clone> SlotDuration<T> {
 		match client.get_aux(T::SLOT_KEY)? {
 			Some(v) => <T as codec::Decode>::decode(&mut &v[..])
 				.map(SlotDuration)
-				.ok_or_else(|| {
+				.map_err(|_| {
 					::client::error::Error::Backend({
 						error!(target: "slots", "slot duration kept in invalid format");
 						format!("slot duration kept in invalid format")
diff --git a/substrate/core/executor/Cargo.toml b/substrate/core/executor/Cargo.toml
index 1f9f3947ac..c5b296b866 100644
--- a/substrate/core/executor/Cargo.toml
+++ b/substrate/core/executor/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 derive_more = "0.14.0"
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 runtime_io = { package = "sr-io", path = "../sr-io" }
 primitives = { package = "substrate-primitives", path = "../primitives" }
 trie = { package = "substrate-trie", path = "../trie" }
diff --git a/substrate/core/executor/src/lib.rs b/substrate/core/executor/src/lib.rs
index a6147a320a..065de451c1 100644
--- a/substrate/core/executor/src/lib.rs
+++ b/substrate/core/executor/src/lib.rs
@@ -44,7 +44,7 @@ pub use native_executor::{with_native_environment, NativeExecutor, NativeExecuti
 pub use wasm_runtimes_cache::RuntimesCache;
 pub use state_machine::Externalities;
 pub use runtime_version::{RuntimeVersion, NativeVersion};
-pub use parity_codec::Codec;
+pub use codec::Codec;
 #[doc(hidden)]
 pub use primitives::Blake2Hasher;
 
diff --git a/substrate/core/executor/src/native_executor.rs b/substrate/core/executor/src/native_executor.rs
index f57c331668..765b9f076e 100644
--- a/substrate/core/executor/src/native_executor.rs
+++ b/substrate/core/executor/src/native_executor.rs
@@ -19,7 +19,7 @@ use crate::error::{Error, Result};
 use state_machine::{CodeExecutor, Externalities};
 use crate::wasm_executor::WasmExecutor;
 use runtime_version::{NativeVersion, RuntimeVersion};
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use crate::RuntimeInfo;
 use primitives::{Blake2Hasher, NativeOrEncoded};
 use log::trace;
diff --git a/substrate/core/executor/src/sandbox.rs b/substrate/core/executor/src/sandbox.rs
index 1ce300c38a..6687738abc 100644
--- a/substrate/core/executor/src/sandbox.rs
+++ b/substrate/core/executor/src/sandbox.rs
@@ -20,7 +20,7 @@
 
 use crate::error::{Result, Error};
 use std::{collections::HashMap, rc::Rc};
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use primitives::sandbox as sandbox_primitives;
 use wasmi::{
 	Externals, FuncRef, ImportResolver, MemoryInstance, MemoryRef, Module, ModuleInstance,
@@ -193,7 +193,7 @@ fn trap(msg: &'static str) -> Trap {
 fn deserialize_result(serialized_result: &[u8]) -> std::result::Result<Option<RuntimeValue>, Trap> {
 	use self::sandbox_primitives::{HostError, ReturnValue};
 	let result_val = std::result::Result::<ReturnValue, HostError>::decode(&mut &serialized_result[..])
-		.ok_or_else(|| trap("Decoding Result<ReturnValue, HostError> failed!"))?;
+		.map_err(|_| trap("Decoding Result<ReturnValue, HostError> failed!"))?;
 
 	match result_val {
 		Ok(return_value) => Ok(match return_value {
@@ -361,7 +361,7 @@ fn decode_environment_definition(
 	memories: &[Option<MemoryRef>],
 ) -> std::result::Result<(Imports, GuestToSupervisorFunctionMapping), InstantiationError> {
 	let env_def = sandbox_primitives::EnvironmentDefinition::decode(&mut &raw_env_def[..])
-		.ok_or_else(|| InstantiationError::EnvironmentDefinitionCorrupted)?;
+		.map_err(|_| InstantiationError::EnvironmentDefinitionCorrupted)?;
 
 	let mut func_map = HashMap::new();
 	let mut memories_map = HashMap::new();
diff --git a/substrate/core/executor/src/wasm_executor.rs b/substrate/core/executor/src/wasm_executor.rs
index b776a520d7..637390b2c7 100644
--- a/substrate/core/executor/src/wasm_executor.rs
+++ b/substrate/core/executor/src/wasm_executor.rs
@@ -26,7 +26,7 @@ use wasmi::{
 };
 use state_machine::{Externalities, ChildStorageKey};
 use crate::error::{Error, Result};
-use parity_codec::Encode;
+use codec::Encode;
 use primitives::{blake2_128, blake2_256, twox_64, twox_128, twox_256, ed25519, sr25519, Pair};
 use primitives::offchain;
 use primitives::hexdisplay::HexDisplay;
@@ -1081,7 +1081,7 @@ impl_function_executor!(this: FunctionExecutor<'e, E>,
 		request_id: u32,
 		written_out: *mut u32
 	) -> *mut u8 => {
-		use parity_codec::Encode;
+		use codec::Encode;
 
 		let headers = this.ext.offchain()
 			.map(|api| api.http_response_headers(offchain::HttpRequestId(request_id as u16)))
@@ -1172,7 +1172,7 @@ impl_function_executor!(this: FunctionExecutor<'e, E>,
 		return_val_len: usize,
 		state: usize
 	) -> u32 => {
-		use parity_codec::{Decode, Encode};
+		use codec::{Decode, Encode};
 
 		trace!(target: "sr-sandbox", "invoke, instance_idx={}", instance_idx);
 		let export = this.memory.get(export_ptr, export_len as usize)
@@ -1186,7 +1186,7 @@ impl_function_executor!(this: FunctionExecutor<'e, E>,
 		let serialized_args = this.memory.get(args_ptr, args_len as usize)
 			.map_err(|_| "OOB while ext_sandbox_invoke: args")?;
 		let args = Vec::<sandbox_primitives::TypedValue>::decode(&mut &serialized_args[..])
-			.ok_or_else(|| "Can't decode serialized arguments for the invocation")?
+			.map_err(|_| "Can't decode serialized arguments for the invocation")?
 			.into_iter()
 			.map(Into::into)
 			.collect::<Vec<_>>();
@@ -1443,7 +1443,7 @@ impl WasmExecutor {
 mod tests {
 	use super::*;
 
-	use parity_codec::Encode;
+	use codec::Encode;
 
 	use state_machine::TestExternalities as CoreTestExternalities;
 	use hex_literal::hex;
diff --git a/substrate/core/executor/src/wasm_runtimes_cache.rs b/substrate/core/executor/src/wasm_runtimes_cache.rs
index a1540204c7..812638126d 100644
--- a/substrate/core/executor/src/wasm_runtimes_cache.rs
+++ b/substrate/core/executor/src/wasm_runtimes_cache.rs
@@ -19,7 +19,7 @@
 use crate::error::Error;
 use crate::wasm_executor::WasmExecutor;
 use log::{trace, warn};
-use parity_codec::Decode;
+use codec::Decode;
 use parity_wasm::elements::{deserialize_buffer, DataSegment, Instruction, Module as RawModule};
 use primitives::storage::well_known_keys;
 use primitives::Blake2Hasher;
@@ -288,7 +288,7 @@ impl RuntimesCache {
 
 		let heap_pages = ext
 			.storage(well_known_keys::HEAP_PAGES)
-			.and_then(|pages| u64::decode(&mut &pages[..]))
+			.and_then(|pages| u64::decode(&mut &pages[..]).ok())
 			.or(default_heap_pages)
 			.unwrap_or(DEFAULT_HEAP_PAGES);
 
@@ -308,7 +308,7 @@ impl RuntimesCache {
 		let version = wasm_executor
 			.call_in_wasm_module(ext, &instance, "Core_version", &[])
 			.ok()
-			.and_then(|v| RuntimeVersion::decode(&mut v.as_slice()));
+			.and_then(|v| RuntimeVersion::decode(&mut v.as_slice()).ok());
 		Ok(Rc::new(CachedRuntime {
 			instance,
 			version,
diff --git a/substrate/core/finality-grandpa/Cargo.toml b/substrate/core/finality-grandpa/Cargo.toml
index 8477f75edd..04f9e7162c 100644
--- a/substrate/core/finality-grandpa/Cargo.toml
+++ b/substrate/core/finality-grandpa/Cargo.toml
@@ -13,7 +13,7 @@ parking_lot = "0.8.0"
 tokio-executor = "0.1.7"
 tokio-timer = "0.2.11"
 rand = "0.6"
-parity-codec = { version = "4.1.1", features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
 sr-primitives = {  path = "../sr-primitives" }
 consensus_common = { package = "substrate-consensus-common", path = "../consensus/common" }
 primitives = { package = "substrate-primitives",  path = "../primitives" }
@@ -25,10 +25,10 @@ network = { package = "substrate-network", path = "../network" }
 service = { package = "substrate-service", path = "../service", optional = true }
 srml-finality-tracker = { path = "../../srml/finality-tracker" }
 fg_primitives = { package = "substrate-finality-grandpa-primitives", path = "primitives" }
-grandpa = { package = "finality-grandpa", version = "0.8.1", features = ["derive-codec"] }
+grandpa = { package = "finality-grandpa", version = "0.9.0", features = ["derive-codec"] }
 
 [dev-dependencies]
-grandpa = { package = "finality-grandpa", version = "0.8.1", features = ["derive-codec", "test-helpers"] }
+grandpa = { package = "finality-grandpa", version = "0.9.0", features = ["derive-codec", "test-helpers"] }
 network = { package = "substrate-network", path = "../network", features = ["test-helpers"] }
 keyring = { package = "substrate-keyring", path = "../keyring" }
 test-client = { package = "substrate-test-runtime-client", path = "../test-runtime/client"}
diff --git a/substrate/core/finality-grandpa/primitives/Cargo.toml b/substrate/core/finality-grandpa/primitives/Cargo.toml
index 75e6b5f608..1c17639a2a 100644
--- a/substrate/core/finality-grandpa/primitives/Cargo.toml
+++ b/substrate/core/finality-grandpa/primitives/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 client = { package = "substrate-client", path = "../../client", default-features = false }
 primitives = { package = "substrate-primitives",  path = "../../primitives", default-features = false }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 sr-primitives = { path = "../../sr-primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../sr-std", default-features = false }
 serde = { version = "1.0", optional = true, features = ["derive"] }
@@ -17,7 +17,7 @@ default = ["std"]
 std = [
 	"primitives/std",
 	"client/std",
-	"parity-codec/std",
+	"codec/std",
 	"sr-primitives/std",
 	"rstd/std",
 	"serde",
diff --git a/substrate/core/finality-grandpa/primitives/src/lib.rs b/substrate/core/finality-grandpa/primitives/src/lib.rs
index b60acffc6c..25f8b802ce 100644
--- a/substrate/core/finality-grandpa/primitives/src/lib.rs
+++ b/substrate/core/finality-grandpa/primitives/src/lib.rs
@@ -23,7 +23,7 @@ extern crate alloc;
 
 #[cfg(feature = "std")]
 use serde::Serialize;
-use parity_codec::{Encode, Decode, Codec};
+use codec::{Encode, Decode, Codec};
 use sr_primitives::{ConsensusEngineId, traits::{DigestFor, NumberFor}};
 use client::decl_runtime_apis;
 use rstd::vec::Vec;
diff --git a/substrate/core/finality-grandpa/src/authorities.rs b/substrate/core/finality-grandpa/src/authorities.rs
index 8b329d4116..27b9c57073 100644
--- a/substrate/core/finality-grandpa/src/authorities.rs
+++ b/substrate/core/finality-grandpa/src/authorities.rs
@@ -19,7 +19,7 @@
 use fork_tree::ForkTree;
 use parking_lot::RwLock;
 use grandpa::voter_set::VoterSet;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use log::{debug, info};
 use substrate_telemetry::{telemetry, CONSENSUS_INFO};
 use fg_primitives::AuthorityId;
@@ -403,7 +403,7 @@ pub(crate) struct PendingChange<H, N> {
 }
 
 impl<H: Decode, N: Decode> Decode for PendingChange<H, N> {
-	fn decode<I: parity_codec::Input>(value: &mut I) -> Option<Self> {
+	fn decode<I: codec::Input>(value: &mut I) -> Result<Self, codec::Error> {
 		let next_authorities = Decode::decode(value)?;
 		let delay = Decode::decode(value)?;
 		let canon_height = Decode::decode(value)?;
@@ -411,7 +411,7 @@ impl<H: Decode, N: Decode> Decode for PendingChange<H, N> {
 
 		let delay_kind = DelayKind::decode(value).unwrap_or(DelayKind::Finalized);
 
-		Some(PendingChange {
+		Ok(PendingChange {
 			next_authorities,
 			delay,
 			canon_height,
diff --git a/substrate/core/finality-grandpa/src/aux_schema.rs b/substrate/core/finality-grandpa/src/aux_schema.rs
index 528a221c35..5f430b17fe 100644
--- a/substrate/core/finality-grandpa/src/aux_schema.rs
+++ b/substrate/core/finality-grandpa/src/aux_schema.rs
@@ -18,7 +18,7 @@
 
 use std::fmt::Debug;
 use std::sync::Arc;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use client::backend::AuxStore;
 use client::error::{Result as ClientResult, Error as ClientError};
 use fork_tree::ForkTree;
@@ -108,8 +108,8 @@ pub(crate) fn load_decode<B: AuxStore, T: Decode>(backend: &B, key: &[u8]) -> Cl
 	match backend.get_aux(key)? {
 		None => Ok(None),
 		Some(t) => T::decode(&mut &t[..])
-			.ok_or_else(
-				|| ClientError::Backend(format!("GRANDPA DB is corrupted.")),
+			.map_err(
+				|e| ClientError::Backend(format!("GRANDPA DB is corrupted: {}", e.what())),
 			)
 			.map(Some)
 	}
diff --git a/substrate/core/finality-grandpa/src/communication/gossip.rs b/substrate/core/finality-grandpa/src/communication/gossip.rs
index 3d14381e72..e51e23254c 100644
--- a/substrate/core/finality-grandpa/src/communication/gossip.rs
+++ b/substrate/core/finality-grandpa/src/communication/gossip.rs
@@ -85,7 +85,7 @@
 use sr_primitives::traits::{NumberFor, Block as BlockT, Zero};
 use network::consensus_gossip::{self as network_gossip, MessageIntent, ValidatorContext};
 use network::{config::Roles, PeerId};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use crate::ed25519::Public as AuthorityId;
 
 use substrate_telemetry::{telemetry, CONSENSUS_DEBUG};
@@ -977,10 +977,10 @@ impl<Block: BlockT> GossipValidator<Block> {
 
 		let action = {
 			match GossipMessage::<Block>::decode(&mut data) {
-				Some(GossipMessage::VoteOrPrecommit(ref message))
+				Ok(GossipMessage::VoteOrPrecommit(ref message))
 					=> self.inner.write().validate_round_message(who, message),
-				Some(GossipMessage::Commit(ref message)) => self.inner.write().validate_commit_message(who, message),
-				Some(GossipMessage::Neighbor(update)) => {
+				Ok(GossipMessage::Commit(ref message)) => self.inner.write().validate_commit_message(who, message),
+				Ok(GossipMessage::Neighbor(update)) => {
 					let (topics, action, catch_up, report) = self.inner.write().import_neighbor_message(
 						who,
 						update.into_neighbor_packet(),
@@ -994,9 +994,9 @@ impl<Block: BlockT> GossipValidator<Block> {
 					peer_reply = catch_up;
 					action
 				}
-				Some(GossipMessage::CatchUp(ref message))
+				Ok(GossipMessage::CatchUp(ref message))
 					=> self.inner.write().validate_catch_up_message(who, message),
-				Some(GossipMessage::CatchUpRequest(request)) => {
+				Ok(GossipMessage::CatchUpRequest(request)) => {
 					let (reply, action) = self.inner.write().handle_catch_up_request(
 						who,
 						request,
@@ -1006,8 +1006,8 @@ impl<Block: BlockT> GossipValidator<Block> {
 					peer_reply = reply;
 					action
 				}
-				None => {
-					debug!(target: "afg", "Error decoding message");
+				Err(e) => {
+					debug!(target: "afg", "Error decoding message: {}", e.what());
 					telemetry!(CONSENSUS_DEBUG; "afg.err_decoding_msg"; "" => "");
 
 					let len = std::cmp::min(i32::max_value() as usize, data.len()) as i32;
@@ -1127,17 +1127,17 @@ impl<Block: BlockT> network_gossip::Validator<Block> for GossipValidator<Block>
 			let peer_best_commit = peer.view.last_commit;
 
 			match GossipMessage::<Block>::decode(&mut data) {
-				None => false,
-				Some(GossipMessage::Commit(full)) => {
+				Err(_) => false,
+				Ok(GossipMessage::Commit(full)) => {
 					// we only broadcast our best commit and only if it's
 					// better than last received by peer.
 					Some(full.message.target_number) == our_best_commit
 					&& Some(full.message.target_number) > peer_best_commit
 				}
-				Some(GossipMessage::Neighbor(_)) => false,
-				Some(GossipMessage::CatchUpRequest(_)) => false,
-				Some(GossipMessage::CatchUp(_)) => false,
-				Some(GossipMessage::VoteOrPrecommit(_)) => false, // should not be the case.
+				Ok(GossipMessage::Neighbor(_)) => false,
+				Ok(GossipMessage::CatchUpRequest(_)) => false,
+				Ok(GossipMessage::CatchUp(_)) => false,
+				Ok(GossipMessage::VoteOrPrecommit(_)) => false, // should not be the case.
 			}
 		})
 	}
@@ -1162,10 +1162,10 @@ impl<Block: BlockT> network_gossip::Validator<Block> for GossipValidator<Block>
 			let best_commit = local_view.last_commit;
 
 			match GossipMessage::<Block>::decode(&mut data) {
-				None => true,
-				Some(GossipMessage::Commit(full))
+				Err(_) => true,
+				Ok(GossipMessage::Commit(full))
 					=> Some(full.message.target_number) != best_commit,
-				Some(_) => true,
+				Ok(_) => true,
 			}
 		})
 	}
diff --git a/substrate/core/finality-grandpa/src/communication/mod.rs b/substrate/core/finality-grandpa/src/communication/mod.rs
index e9be187eac..607dba486d 100644
--- a/substrate/core/finality-grandpa/src/communication/mod.rs
+++ b/substrate/core/finality-grandpa/src/communication/mod.rs
@@ -35,7 +35,7 @@ use futures::prelude::*;
 use futures::sync::{oneshot, mpsc};
 use log::{debug, trace};
 use tokio_executor::Executor;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use primitives::{ed25519, Pair};
 use substrate_telemetry::{telemetry, CONSENSUS_DEBUG, CONSENSUS_INFO};
 use sr_primitives::traits::{Block as BlockT, Hash as HashT, Header as HeaderT};
@@ -367,10 +367,10 @@ impl<B: BlockT, N: Network<B>> NetworkBridge<B, N> {
 		let incoming = self.service.messages_for(topic)
 			.filter_map(|notification| {
 				let decoded = GossipMessage::<B>::decode(&mut &notification.message[..]);
-				if decoded.is_none() {
-					debug!(target: "afg", "Skipping malformed message {:?}", notification);
+				if let Err(ref e) = decoded {
+					debug!(target: "afg", "Skipping malformed message {:?}: {}", notification, e);
 				}
-				decoded
+				decoded.ok()
 			})
 			.and_then(move |msg| {
 				match msg {
@@ -583,10 +583,10 @@ fn incoming_global<B: BlockT, N: Network<B>>(
 		.filter_map(|notification| {
 			// this could be optimized by decoding piecewise.
 			let decoded = GossipMessage::<B>::decode(&mut &notification.message[..]);
-			if decoded.is_none() {
-				trace!(target: "afg", "Skipping malformed commit message {:?}", notification);
+			if let Err(ref e) = decoded {
+				trace!(target: "afg", "Skipping malformed commit message {:?}: {}", notification, e);
 			}
-			decoded.map(move |d| (notification, d))
+			decoded.map(move |d| (notification, d)).ok()
 		})
 		.filter_map(move |(notification, msg)| {
 			match msg {
diff --git a/substrate/core/finality-grandpa/src/communication/periodic.rs b/substrate/core/finality-grandpa/src/communication/periodic.rs
index cae42d0dc7..7265fe34a2 100644
--- a/substrate/core/finality-grandpa/src/communication/periodic.rs
+++ b/substrate/core/finality-grandpa/src/communication/periodic.rs
@@ -23,7 +23,7 @@ use sr_primitives::traits::{NumberFor, Block as BlockT};
 use network::PeerId;
 use tokio_timer::Delay;
 use log::warn;
-use parity_codec::Encode;
+use codec::Encode;
 
 use std::time::{Instant, Duration};
 
diff --git a/substrate/core/finality-grandpa/src/communication/tests.rs b/substrate/core/finality-grandpa/src/communication/tests.rs
index cfe41acb3c..f1473e9863 100644
--- a/substrate/core/finality-grandpa/src/communication/tests.rs
+++ b/substrate/core/finality-grandpa/src/communication/tests.rs
@@ -24,7 +24,7 @@ use network_gossip::Validator;
 use tokio::runtime::current_thread;
 use std::sync::Arc;
 use keyring::Ed25519Keyring;
-use parity_codec::Encode;
+use codec::Encode;
 
 use crate::environment::SharedVoterSetState;
 use super::gossip::{self, GossipValidator};
diff --git a/substrate/core/finality-grandpa/src/consensus_changes.rs b/substrate/core/finality-grandpa/src/consensus_changes.rs
index 02ac951241..4d94224892 100644
--- a/substrate/core/finality-grandpa/src/consensus_changes.rs
+++ b/substrate/core/finality-grandpa/src/consensus_changes.rs
@@ -15,7 +15,7 @@
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
 use std::sync::Arc;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 
 /// Consensus-related data changes tracker.
 #[derive(Clone, Debug, Encode, Decode)]
diff --git a/substrate/core/finality-grandpa/src/environment.rs b/substrate/core/finality-grandpa/src/environment.rs
index 3090cff386..1949fd25a1 100644
--- a/substrate/core/finality-grandpa/src/environment.rs
+++ b/substrate/core/finality-grandpa/src/environment.rs
@@ -20,7 +20,7 @@ use std::sync::Arc;
 use std::time::{Duration, Instant};
 
 use log::{debug, warn, info};
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use futures::prelude::*;
 use tokio_timer::Delay;
 use parking_lot::RwLock;
@@ -95,8 +95,10 @@ impl<Block: BlockT> Encode for CompletedRounds<Block> {
 	}
 }
 
+impl<Block: BlockT> codec::EncodeLike for CompletedRounds<Block> {}
+
 impl<Block: BlockT> Decode for CompletedRounds<Block> {
-	fn decode<I: parity_codec::Input>(value: &mut I) -> Option<Self> {
+	fn decode<I: codec::Input>(value: &mut I) -> Result<Self, codec::Error> {
 		<(Vec<CompletedRound<Block>>, u64, Vec<AuthorityId>)>::decode(value)
 			.map(|(rounds, set_id, voters)| CompletedRounds {
 				rounds: rounds.into(),
diff --git a/substrate/core/finality-grandpa/src/finality_proof.rs b/substrate/core/finality-grandpa/src/finality_proof.rs
index f174fb04f6..830383ffca 100644
--- a/substrate/core/finality-grandpa/src/finality_proof.rs
+++ b/substrate/core/finality-grandpa/src/finality_proof.rs
@@ -43,7 +43,7 @@ use client::{
 	light::fetcher::{FetchChecker, RemoteCallRequest},
 	ExecutionStrategy, NeverOffchainExt,
 };
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use grandpa::BlockNumberOps;
 use sr_primitives::{Justification, generic::BlockId};
 use sr_primitives::traits::{
@@ -81,8 +81,8 @@ impl<B, E, Block: BlockT<Hash=H256>, RA> AuthoritySetForFinalityProver<Block> fo
 			ExecutionStrategy::NativeElseWasm,
 			NeverOffchainExt::new(),
 		).and_then(|call_result| Decode::decode(&mut &call_result[..])
-			.ok_or_else(|| ClientError::CallResultDecode(
-				"failed to decode GRANDPA authorities set proof".into(),
+			.map_err(|err| ClientError::CallResultDecode(
+				"failed to decode GRANDPA authorities set proof".into(), err
 			)))
 	}
 
@@ -121,8 +121,8 @@ impl<Block: BlockT> AuthoritySetForFinalityChecker<Block> for Arc<dyn FetchCheck
 		self.check_execution_proof(&request, proof)
 			.and_then(|authorities| {
 				let authorities: Vec<(AuthorityId, u64)> = Decode::decode(&mut &authorities[..])
-					.ok_or_else(|| ClientError::CallResultDecode(
-						"failed to decode GRANDPA authorities set proof".into(),
+					.map_err(|err| ClientError::CallResultDecode(
+						"failed to decode GRANDPA authorities set proof".into(), err
 					))?;
 				Ok(authorities.into_iter().collect())
 			})
@@ -167,8 +167,8 @@ impl<B, E, Block, RA> network::FinalityProofProvider<Block> for FinalityProofPro
 		request: &[u8],
 	) -> Result<Option<Vec<u8>>, ClientError> {
 		let request: FinalityProofRequest<Block::Hash> = Decode::decode(&mut &request[..])
-			.ok_or_else(|| {
-				warn!(target: "finality", "Unable to decode finality proof request.");
+			.map_err(|e| {
+				warn!(target: "finality", "Unable to decode finality proof request: {}", e.what());
 				ClientError::Backend(format!("Invalid finality proof request"))
 			})?;
 		match request {
@@ -445,7 +445,7 @@ fn do_check_finality_proof<Block: BlockT<Hash=H256>, B, J>(
 {
 	// decode finality proof
 	let proof = FinalityProof::<Block::Header>::decode(&mut &remote_proof[..])
-		.ok_or_else(|| ClientError::BadJustification("failed to decode finality proof".into()))?;
+		.map_err(|_| ClientError::BadJustification("failed to decode finality proof".into()))?;
 
 	// empty proof can't prove anything
 	if proof.is_empty() {
@@ -500,7 +500,7 @@ fn check_finality_proof_fragment<Block: BlockT<Hash=H256>, B, J>(
 	// verify justification using previous authorities set
 	let (mut current_set_id, mut current_authorities) = authority_set.extract_authorities();
 	let justification: J = Decode::decode(&mut &proof_fragment.justification[..])
-		.ok_or_else(|| ClientError::JustificationDecode)?;
+		.map_err(|_| ClientError::JustificationDecode)?;
 	justification.verify(current_set_id, &current_authorities)?;
 
 	// and now verify new authorities proof (if provided)
@@ -560,7 +560,8 @@ pub(crate) trait ProvableJustification<Header: HeaderT>: Encode + Decode {
 		set_id: u64,
 		authorities: &[(AuthorityId, u64)],
 	) -> ClientResult<Self> {
-		let justification = Self::decode(&mut &**justification).ok_or(ClientError::JustificationDecode)?;
+		let justification = Self::decode(&mut &**justification)
+			.map_err(|_| ClientError::JustificationDecode)?;
 		justification.verify(set_id, authorities)?;
 		Ok(justification)
 	}
diff --git a/substrate/core/finality-grandpa/src/import.rs b/substrate/core/finality-grandpa/src/import.rs
index 91e2b92182..4144a279c5 100644
--- a/substrate/core/finality-grandpa/src/import.rs
+++ b/substrate/core/finality-grandpa/src/import.rs
@@ -17,7 +17,7 @@
 use std::{sync::Arc, collections::HashMap};
 
 use log::{debug, trace, info};
-use parity_codec::Encode;
+use codec::Encode;
 use futures::sync::mpsc;
 use parking_lot::RwLockWriteGuard;
 
diff --git a/substrate/core/finality-grandpa/src/justification.rs b/substrate/core/finality-grandpa/src/justification.rs
index 59a3d2166c..a6554b1e90 100644
--- a/substrate/core/finality-grandpa/src/justification.rs
+++ b/substrate/core/finality-grandpa/src/justification.rs
@@ -20,7 +20,7 @@ use client::{CallExecutor, Client};
 use client::backend::Backend;
 use client::blockchain::HeaderBackend;
 use client::error::Error as ClientError;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use grandpa::voter_set::VoterSet;
 use grandpa::{Error as GrandpaError};
 use sr_primitives::generic::BlockId;
@@ -104,7 +104,7 @@ impl<Block: BlockT<Hash=H256>> GrandpaJustification<Block> {
 	{
 
 		let justification = GrandpaJustification::<Block>::decode(&mut &*encoded)
-			.ok_or(ClientError::JustificationDecode)?;
+			.map_err(|_| ClientError::JustificationDecode)?;
 
 		if (justification.commit.target_hash, justification.commit.target_number) != finalized_target {
 			let msg = "invalid commit target in grandpa justification".to_string();
diff --git a/substrate/core/finality-grandpa/src/lib.rs b/substrate/core/finality-grandpa/src/lib.rs
index 2e688ed952..0d04e964e2 100644
--- a/substrate/core/finality-grandpa/src/lib.rs
+++ b/substrate/core/finality-grandpa/src/lib.rs
@@ -57,7 +57,7 @@ use log::{debug, info, warn};
 use futures::sync::mpsc;
 use client::{BlockchainEvents, CallExecutor, Client, backend::Backend, error::Error as ClientError};
 use client::blockchain::HeaderBackend;
-use parity_codec::Encode;
+use codec::Encode;
 use sr_primitives::traits::{
 	NumberFor, Block as BlockT, DigestFor, ProvideRuntimeApi,
 };
diff --git a/substrate/core/finality-grandpa/src/light_import.rs b/substrate/core/finality-grandpa/src/light_import.rs
index abc98976fd..3fec523dcb 100644
--- a/substrate/core/finality-grandpa/src/light_import.rs
+++ b/substrate/core/finality-grandpa/src/light_import.rs
@@ -25,7 +25,7 @@ use client::{
 	blockchain::HeaderBackend,
 	error::Error as ClientError,
 };
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use consensus_common::{
 	import_queue::Verifier, well_known_cache_keys,
 	BlockOrigin, BlockImport, FinalityProofImport, BlockImportParams, ImportResult, ImportedAux,
diff --git a/substrate/core/finality-grandpa/src/tests.rs b/substrate/core/finality-grandpa/src/tests.rs
index 797463f5de..38a5dd5441 100644
--- a/substrate/core/finality-grandpa/src/tests.rs
+++ b/substrate/core/finality-grandpa/src/tests.rs
@@ -34,7 +34,7 @@ use consensus_common::{BlockOrigin, ForkChoiceStrategy, ImportedAux, BlockImport
 use consensus_common::import_queue::{BoxBlockImport, BoxJustificationImport, BoxFinalityProofImport};
 use std::collections::{HashMap, HashSet};
 use std::result;
-use parity_codec::Decode;
+use codec::Decode;
 use sr_primitives::traits::{ApiRef, ProvideRuntimeApi, Header as HeaderT};
 use sr_primitives::generic::BlockId;
 use primitives::{NativeOrEncoded, ExecutionContext};
@@ -336,7 +336,7 @@ impl AuthoritySetForFinalityChecker<Block> for TestApi {
 		proof: Vec<Vec<u8>>,
 	) -> Result<Vec<(AuthorityId, u64)>> {
 		Decode::decode(&mut &proof[0][..])
-			.ok_or_else(|| unreachable!("incorrect value is passed as GRANDPA authorities proof"))
+			.map_err(|_| unreachable!("incorrect value is passed as GRANDPA authorities proof"))
 	}
 }
 
diff --git a/substrate/core/inherents/Cargo.toml b/substrate/core/inherents/Cargo.toml
index 7174b7acea..f89288578a 100644
--- a/substrate/core/inherents/Cargo.toml
+++ b/substrate/core/inherents/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 parking_lot = { version = "0.8.0", optional = true }
 rstd = { package = "sr-std", path = "../sr-std", default-features = false }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 sr-primitives = {  path = "../sr-primitives", default-features = false }
 
 [features]
@@ -15,6 +15,6 @@ default = [ "std" ]
 std = [
 	"parking_lot",
 	"rstd/std",
-	"parity-codec/std",
+	"codec/std",
 	"sr-primitives/std",
 ]
diff --git a/substrate/core/inherents/src/lib.rs b/substrate/core/inherents/src/lib.rs
index a5dcfdffcf..f7363b483b 100644
--- a/substrate/core/inherents/src/lib.rs
+++ b/substrate/core/inherents/src/lib.rs
@@ -33,7 +33,6 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 #![warn(missing_docs)]
 
-use parity_codec as codec;
 use codec::{Encode, Decode};
 
 use rstd::{collections::btree_map::{BTreeMap, IntoIter, Entry}, vec::Vec};
@@ -52,7 +51,7 @@ pub type InherentIdentifier = [u8; 8];
 /// Inherent data to include in a block.
 #[derive(Clone, Default, Encode, Decode)]
 pub struct InherentData {
-	/// All inherent data encoded with parity-codec and an identifier.
+	/// All inherent data encoded with parity-scale-codec and an identifier.
 	data: BTreeMap<InherentIdentifier, Vec<u8>>
 }
 
@@ -111,7 +110,7 @@ impl InherentData {
 		match self.data.get(identifier) {
 			Some(inherent) =>
 				I::decode(&mut &inherent[..])
-					.ok_or_else(|| {
+					.map_err(|_| {
 						"Could not decode requested inherent type!".into()
 					})
 					.map(Some),
diff --git a/substrate/core/network/Cargo.toml b/substrate/core/network/Cargo.toml
index 3d687486c0..383fc29fc6 100644
--- a/substrate/core/network/Cargo.toml
+++ b/substrate/core/network/Cargo.toml
@@ -28,7 +28,7 @@ consensus = { package = "substrate-consensus-common", path = "../../core/consens
 client = { package = "substrate-client", path = "../../core/client" }
 sr-primitives = { path = "../../core/sr-primitives" }
 primitives = { package = "substrate-primitives", path = "../../core/primitives" }
-parity-codec = { version = "4.1.1", features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
 peerset = { package = "substrate-peerset", path = "../../core/peerset" }
 serde = { version = "1.0.70", features = ["derive"] }
 serde_json = "1.0.24"
diff --git a/substrate/core/network/src/config.rs b/substrate/core/network/src/config.rs
index 13e9a0d3a5..c05c127d83 100644
--- a/substrate/core/network/src/config.rs
+++ b/substrate/core/network/src/config.rs
@@ -27,7 +27,6 @@ use crate::on_demand_layer::OnDemand;
 use crate::service::{ExHashT, TransactionPool};
 use bitflags::bitflags;
 use consensus::import_queue::ImportQueue;
-use parity_codec;
 use sr_primitives::traits::{Block as BlockT};
 use std::sync::Arc;
 use libp2p::identity::{Keypair, secp256k1, ed25519};
@@ -109,15 +108,17 @@ impl Roles {
 	}
 }
 
-impl parity_codec::Encode for Roles {
-	fn encode_to<T: parity_codec::Output>(&self, dest: &mut T) {
+impl codec::Encode for Roles {
+	fn encode_to<T: codec::Output>(&self, dest: &mut T) {
 		dest.push_byte(self.bits())
 	}
 }
 
-impl parity_codec::Decode for Roles {
-	fn decode<I: parity_codec::Input>(input: &mut I) -> Option<Self> {
-		Self::from_bits(input.read_byte()?)
+impl codec::EncodeLike for Roles {}
+
+impl codec::Decode for Roles {
+	fn decode<I: codec::Input>(input: &mut I) -> Result<Self, codec::Error> {
+		Self::from_bits(input.read_byte()?).ok_or_else(|| codec::Error::from("Invalid bytes"))
 	}
 }
 
diff --git a/substrate/core/network/src/custom_proto/upgrade.rs b/substrate/core/network/src/custom_proto/upgrade.rs
index 1959ca2883..ebd9c431e0 100644
--- a/substrate/core/network/src/custom_proto/upgrade.rs
+++ b/substrate/core/network/src/custom_proto/upgrade.rs
@@ -22,7 +22,7 @@ use libp2p::tokio_codec::Framed;
 use log::warn;
 use std::{collections::VecDeque, io, marker::PhantomData, vec::IntoIter as VecIntoIter};
 use futures::{prelude::*, future, stream};
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use sr_primitives::traits::Block as BlockT;
 use tokio_io::{AsyncRead, AsyncWrite};
 use unsigned_varint::codec::UviBytes;
@@ -179,7 +179,7 @@ where TSubstream: AsyncRead + AsyncWrite, B: BlockT {
 				self.clogged_fuse = true;
 				return Ok(Async::Ready(Some(RegisteredProtocolEvent::Clogged {
 					messages: self.send_queue.iter()
-						.map(|m| Decode::decode(&mut &m[..]).ok_or(()))
+						.map(|m| Decode::decode(&mut &m[..]))
 						.filter_map(Result::ok)
 						.collect(),
 				})))
@@ -199,9 +199,12 @@ where TSubstream: AsyncRead + AsyncWrite, B: BlockT {
 		// Note that `inner` is wrapped in a `Fuse`, therefore we can poll it forever.
 		match self.inner.poll()? {
 			Async::Ready(Some(data)) => {
-				let message = <Message<B> as Decode>::decode(&mut &data[..]).ok_or(())
-					.map_err(|()| {
-						warn!(target: "sub-libp2p", "Couldn't decode packet sent by the remote: {:?}", data);
+				let message = <Message<B> as Decode>::decode(&mut &data[..])
+					.map_err(|err| {
+						warn!(
+							target: "sub-libp2p",
+							"Couldn't decode packet sent by the remote: {:?}: {}", data, err.what(),
+						);
 						io::ErrorKind::InvalidData
 					})?;
 				Ok(Async::Ready(Some(RegisteredProtocolEvent::Message(message))))
diff --git a/substrate/core/network/src/protocol/message.rs b/substrate/core/network/src/protocol/message.rs
index def9d4c225..4110970f99 100644
--- a/substrate/core/network/src/protocol/message.rs
+++ b/substrate/core/network/src/protocol/message.rs
@@ -18,7 +18,7 @@
 
 use bitflags::bitflags;
 use sr_primitives::{ConsensusEngineId, traits::{Block as BlockT, Header as HeaderT}};
-use parity_codec::{Encode, Decode, Input, Output};
+use codec::{Encode, Decode, Input, Output, Error};
 pub use self::generic::{
 	BlockAnnounce, RemoteCallRequest, RemoteReadRequest,
 	RemoteHeaderRequest, RemoteHeaderResponse,
@@ -90,9 +90,11 @@ impl Encode for BlockAttributes {
 	}
 }
 
+impl codec::EncodeLike for BlockAttributes {}
+
 impl Decode for BlockAttributes {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
-		Self::from_bits(input.read_byte()?)
+	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
+		Self::from_bits(input.read_byte()?).ok_or_else(|| Error::from("Invalid bytes"))
 	}
 }
 
@@ -125,7 +127,7 @@ pub struct RemoteReadResponse {
 
 /// Generic types.
 pub mod generic {
-	use parity_codec::{Encode, Decode};
+	use codec::{Encode, Decode};
 	use sr_primitives::Justification;
 	use crate::config::Roles;
 	use super::{
diff --git a/substrate/core/offchain/Cargo.toml b/substrate/core/offchain/Cargo.toml
index 694ce38663..97a6fd3d2d 100644
--- a/substrate/core/offchain/Cargo.toml
+++ b/substrate/core/offchain/Cargo.toml
@@ -11,7 +11,7 @@ client = { package = "substrate-client", path = "../../core/client" }
 futures = "0.1.25"
 log = "0.4"
 offchain-primitives = { package = "substrate-offchain-primitives", path = "./primitives" }
-parity-codec = { version = "4.1.1", features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
 parking_lot = "0.8.0"
 primitives = { package = "substrate-primitives", path = "../../core/primitives" }
 sr-primitives = { path = "../../core/sr-primitives" }
diff --git a/substrate/core/offchain/src/api.rs b/substrate/core/offchain/src/api.rs
index 8af7b333f5..8733f3699a 100644
--- a/substrate/core/offchain/src/api.rs
+++ b/substrate/core/offchain/src/api.rs
@@ -25,7 +25,7 @@ use client::backend::OffchainStorage;
 use crate::AuthorityKeyProvider;
 use futures::{Stream, Future, sync::mpsc};
 use log::{info, debug, warn, error};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use primitives::offchain::{
 	Timestamp,
 	HttpRequestId, HttpRequestStatus, HttpError,
@@ -219,7 +219,7 @@ impl<Storage, KeyProvider, Block> Api<Storage, KeyProvider, Block> where
 		match key {
 			CryptoKey::LocalKey { id, kind } => {
 				let key = self.db.get(KEYS_PREFIX, &id.encode())
-					.and_then(|key| StoredKey::decode(&mut &*key))
+					.and_then(|key| StoredKey::decode(&mut &*key).ok())
 					.ok_or(())?;
 				if key.kind != kind {
 					warn!(
@@ -266,7 +266,7 @@ where
 		let (id, id_encoded) = loop {
 			let encoded = self.db.get(KEYS_PREFIX, NEXT_ID);
 			let encoded_slice = encoded.as_ref().map(|x| x.as_slice());
-			let new_id = encoded_slice.and_then(|mut x| u16::decode(&mut x)).unwrap_or_default()
+			let new_id = encoded_slice.and_then(|mut x| u16::decode(&mut x).ok()).unwrap_or_default()
 				.checked_add(1)
 				.ok_or(())?;
 			let new_id_encoded = new_id.encode();
@@ -473,14 +473,14 @@ impl TryFrom<OpaqueNetworkState> for NetworkState {
 	fn try_from(state: OpaqueNetworkState) -> Result<Self, Self::Error> {
 		let inner_vec = state.peer_id.0;
 
-		let bytes: Vec<u8> = Decode::decode(&mut &inner_vec[..]).ok_or(())?;
+		let bytes: Vec<u8> = Decode::decode(&mut &inner_vec[..]).map_err(|_| ())?;
 		let peer_id = PeerId::from_bytes(bytes).map_err(|_| ())?;
 
 		let external_addresses: Result<Vec<Multiaddr>, Self::Error> = state.external_addresses
 			.iter()
 			.map(|enc_multiaddr| -> Result<Multiaddr, Self::Error> {
 				let inner_vec = &enc_multiaddr.0;
-				let bytes = <Vec<u8>>::decode(&mut &inner_vec[..]).ok_or(())?;
+				let bytes = <Vec<u8>>::decode(&mut &inner_vec[..]).map_err(|_| ())?;
 				let multiaddr_str = String::from_utf8(bytes).map_err(|_| ())?;
 				let multiaddr = Multiaddr::from_str(&multiaddr_str).map_err(|_| ())?;
 				Ok(multiaddr)
@@ -548,9 +548,9 @@ impl<A: ChainApi> AsyncApi<A> {
 
 	fn submit_extrinsic(&mut self, ext: Vec<u8>) {
 		let xt = match <A::Block as traits::Block>::Extrinsic::decode(&mut &*ext) {
-			Some(xt) => xt,
-			None => {
-				warn!("Unable to decode extrinsic: {:?}", ext);
+			Ok(xt) => xt,
+			Err(e) => {
+				warn!("Unable to decode extrinsic: {:?}: {}", ext, e.what());
 				return
 			},
 		};
diff --git a/substrate/core/primitives/Cargo.toml b/substrate/core/primitives/Cargo.toml
index d0cdf34141..c927ddfeb6 100644
--- a/substrate/core/primitives/Cargo.toml
+++ b/substrate/core/primitives/Cargo.toml
@@ -6,12 +6,12 @@ edition = "2018"
 
 [dependencies]
 rstd = { package = "sr-std", path = "../sr-std", default-features = false }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rustc-hex = { version = "2.0", default-features = false }
 serde = { version = "1.0", optional = true, features = ["derive"] }
 twox-hash = { version = "1.2.0", optional = true }
 byteorder = { version = "1.3.1", default-features = false }
-primitive-types = { version = "0.4.0", default-features = false, features = ["codec"] }
+primitive-types = { version = "0.5.0", default-features = false, features = ["codec"] }
 impl-serde = { version = "0.1", optional = true }
 wasmi = { version = "0.5.0", optional = true }
 hash-db = { version = "0.15.0", default-features = false }
@@ -57,7 +57,7 @@ std = [
 	"primitive-types/rustc-hex",
 	"primitive-types/libc",
 	"impl-serde",
-	"parity-codec/std",
+	"codec/std",
 	"hash256-std-hasher/std",
 	"hash-db/std",
 	"rstd/std",
diff --git a/substrate/core/primitives/src/changes_trie.rs b/substrate/core/primitives/src/changes_trie.rs
index eb6a75454f..fb7791f0a0 100644
--- a/substrate/core/primitives/src/changes_trie.rs
+++ b/substrate/core/primitives/src/changes_trie.rs
@@ -18,7 +18,7 @@
 
 #[cfg(any(feature = "std", test))]
 use serde::{Serialize, Deserialize};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use num_traits::Zero;
 
 /// Substrate changes trie configuration.
diff --git a/substrate/core/primitives/src/crypto.rs b/substrate/core/primitives/src/crypto.rs
index 327a8a3eb1..b3469e09b8 100644
--- a/substrate/core/primitives/src/crypto.rs
+++ b/substrate/core/primitives/src/crypto.rs
@@ -25,7 +25,7 @@ use parking_lot::Mutex;
 #[cfg(feature = "std")]
 use rand::{RngCore, rngs::OsRng};
 #[cfg(feature = "std")]
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 #[cfg(feature = "std")]
 use regex::Regex;
 #[cfg(feature = "std")]
diff --git a/substrate/core/primitives/src/ed25519.rs b/substrate/core/primitives/src/ed25519.rs
index 5d1fe884a5..0ff0042911 100644
--- a/substrate/core/primitives/src/ed25519.rs
+++ b/substrate/core/primitives/src/ed25519.rs
@@ -20,7 +20,7 @@
 
 
 use crate::{hash::H256, hash::H512};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 
 #[cfg(feature = "std")]
 use blake2_rfc;
diff --git a/substrate/core/primitives/src/lib.rs b/substrate/core/primitives/src/lib.rs
index 4fabb04ccb..bf1911dad9 100644
--- a/substrate/core/primitives/src/lib.rs
+++ b/substrate/core/primitives/src/lib.rs
@@ -33,7 +33,7 @@ macro_rules! map {
 
 use rstd::prelude::*;
 use rstd::ops::Deref;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 #[cfg(feature = "std")]
 use std::borrow::Cow;
 #[cfg(feature = "std")]
@@ -138,14 +138,14 @@ pub enum NativeOrEncoded<R> {
 }
 
 #[cfg(feature = "std")]
-impl<R: parity_codec::Encode> ::std::fmt::Debug for NativeOrEncoded<R> {
+impl<R: codec::Encode> ::std::fmt::Debug for NativeOrEncoded<R> {
 	fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
 		self.as_encoded().as_ref().fmt(f)
 	}
 }
 
 #[cfg(feature = "std")]
-impl<R: parity_codec::Encode> NativeOrEncoded<R> {
+impl<R: codec::Encode> NativeOrEncoded<R> {
 	/// Return the value as the encoded format.
 	pub fn as_encoded<'a>(&'a self) -> Cow<'a, [u8]> {
 		match self {
@@ -164,13 +164,13 @@ impl<R: parity_codec::Encode> NativeOrEncoded<R> {
 }
 
 #[cfg(feature = "std")]
-impl<R: PartialEq + parity_codec::Decode> PartialEq for NativeOrEncoded<R> {
+impl<R: PartialEq + codec::Decode> PartialEq for NativeOrEncoded<R> {
 	fn eq(&self, other: &Self) -> bool {
 		match (self, other) {
 			(NativeOrEncoded::Native(l), NativeOrEncoded::Native(r)) => l == r,
 			(NativeOrEncoded::Native(n), NativeOrEncoded::Encoded(e)) |
 			(NativeOrEncoded::Encoded(e), NativeOrEncoded::Native(n)) =>
-				Some(n) == parity_codec::Decode::decode(&mut &e[..]).as_ref(),
+				Some(n) == codec::Decode::decode(&mut &e[..]).ok().as_ref(),
 			(NativeOrEncoded::Encoded(l), NativeOrEncoded::Encoded(r)) => l == r,
 		}
 	}
@@ -183,7 +183,7 @@ impl<R: PartialEq + parity_codec::Decode> PartialEq for NativeOrEncoded<R> {
 pub enum NeverNativeValue {}
 
 #[cfg(feature = "std")]
-impl parity_codec::Encode for NeverNativeValue {
+impl codec::Encode for NeverNativeValue {
 	fn encode(&self) -> Vec<u8> {
 		// The enum is not constructable, so this function should never be callable!
 		unreachable!()
@@ -191,8 +191,11 @@ impl parity_codec::Encode for NeverNativeValue {
 }
 
 #[cfg(feature = "std")]
-impl parity_codec::Decode for NeverNativeValue {
-	fn decode<I: parity_codec::Input>(_: &mut I) -> Option<Self> {
-		None
+impl codec::EncodeLike for NeverNativeValue {}
+
+#[cfg(feature = "std")]
+impl codec::Decode for NeverNativeValue {
+	fn decode<I: codec::Input>(_: &mut I) -> Result<Self, codec::Error> {
+		Err("`NeverNativeValue` should never be decoded".into())
 	}
 }
diff --git a/substrate/core/primitives/src/offchain.rs b/substrate/core/primitives/src/offchain.rs
index 5b6f8f5c22..a0ee1c34d1 100644
--- a/substrate/core/primitives/src/offchain.rs
+++ b/substrate/core/primitives/src/offchain.rs
@@ -17,7 +17,7 @@
 //! Offchain workers types
 
 use crate::crypto;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use rstd::prelude::{Vec, Box};
 use rstd::convert::TryFrom;
 
@@ -397,7 +397,7 @@ pub trait Externalities {
 
 	/// Initiates a http request given HTTP verb and the URL.
 	///
-	/// Meta is a future-reserved field containing additional, parity-codec encoded parameters.
+	/// Meta is a future-reserved field containing additional, parity-scale-codec encoded parameters.
 	/// Returns the id of newly started request.
 	fn http_request_start(
 		&mut self,
diff --git a/substrate/core/primitives/src/sandbox.rs b/substrate/core/primitives/src/sandbox.rs
index 773a6b4893..e47a30ca5b 100644
--- a/substrate/core/primitives/src/sandbox.rs
+++ b/substrate/core/primitives/src/sandbox.rs
@@ -16,7 +16,7 @@
 
 //! Definition of a sandbox environment.
 
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use rstd::vec::Vec;
 
 /// Error error that can be returned from host function.
@@ -184,7 +184,7 @@ pub const ERR_EXECUTION: u32 = -3i32 as u32;
 mod tests {
 	use super::*;
 	use std::fmt;
-	use parity_codec::Codec;
+	use codec::Codec;
 
 	fn roundtrip<S: Codec + PartialEq + fmt::Debug>(s: S) {
 		let encoded = s.encode();
diff --git a/substrate/core/primitives/src/sr25519.rs b/substrate/core/primitives/src/sr25519.rs
index e01d989143..f87a0078ef 100644
--- a/substrate/core/primitives/src/sr25519.rs
+++ b/substrate/core/primitives/src/sr25519.rs
@@ -33,7 +33,7 @@ use bip39::{Mnemonic, Language, MnemonicType};
 use crate::crypto::{Pair as TraitPair, DeriveJunction, Infallible, SecretStringError, Derive, Ss58Codec};
 use crate::crypto::{key_types, KeyTypeId, Public as TraitPublic, TypedKey, UncheckedFrom};
 use crate::hash::{H256, H512};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 
 #[cfg(feature = "std")]
 use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
diff --git a/substrate/core/primitives/src/uint.rs b/substrate/core/primitives/src/uint.rs
index dfea51921d..b41596a910 100644
--- a/substrate/core/primitives/src/uint.rs
+++ b/substrate/core/primitives/src/uint.rs
@@ -21,7 +21,7 @@ pub use primitive_types::U256;
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use parity_codec::{Encode, Decode};
+	use codec::{Encode, Decode};
 	use substrate_serializer as ser;
 
 	macro_rules! test {
@@ -78,10 +78,10 @@ mod tests {
 			res2);
 		assert_eq!(
 			U256::decode(&mut &res1[..]),
-			Some(U256::from(120)));
+			Ok(U256::from(120)));
 		assert_eq!(
 			U256::decode(&mut &res2[..]),
-			Some(U256::max_value()));
+			Ok(U256::max_value()));
 	}
 
 	#[test]
diff --git a/substrate/core/rpc/Cargo.toml b/substrate/core/rpc/Cargo.toml
index a94b410775..cf129a03e6 100644
--- a/substrate/core/rpc/Cargo.toml
+++ b/substrate/core/rpc/Cargo.toml
@@ -14,7 +14,7 @@ jsonrpc-pubsub = "12.0.0"
 jsonrpc-derive = "12.0.0"
 log = "0.4"
 parking_lot = "0.8.0"
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 client = { package = "substrate-client", path = "../client" }
diff --git a/substrate/core/rpc/src/author/error.rs b/substrate/core/rpc/src/author/error.rs
index 82ace88b84..769f111105 100644
--- a/substrate/core/rpc/src/author/error.rs
+++ b/substrate/core/rpc/src/author/error.rs
@@ -19,7 +19,6 @@
 use client;
 use transaction_pool::txpool;
 use crate::rpc;
-
 use crate::errors;
 
 /// Author RPC Result type.
@@ -36,8 +35,8 @@ pub enum Error {
 	#[display(fmt="Extrinsic verification error: {}", _0)]
 	Verification(Box<dyn std::error::Error + Send>),
 	/// Incorrect extrinsic format.
-	#[display(fmt="Invalid extrinsic format")]
-	BadFormat,
+	#[display(fmt="Invalid extrinsic format: {}", _0)]
+	BadFormat(codec::Error),
 }
 
 impl std::error::Error for Error {
@@ -78,9 +77,9 @@ impl From<Error> for rpc::Error {
 		use txpool::error::{Error as PoolError};
 
 		match e {
-			Error::BadFormat => rpc::Error {
+			Error::BadFormat(e) => rpc::Error {
 				code: rpc::ErrorCode::ServerError(BAD_FORMAT),
-				message: "Extrinsic has invalid format.".into(),
+				message: format!("Extrinsic has invalid format: {}", e).into(),
 				data: None,
 			},
 			Error::Verification(e) => rpc::Error {
diff --git a/substrate/core/rpc/src/author/mod.rs b/substrate/core/rpc/src/author/mod.rs
index 4e64ff0ce2..aa238aeb70 100644
--- a/substrate/core/rpc/src/author/mod.rs
+++ b/substrate/core/rpc/src/author/mod.rs
@@ -30,7 +30,7 @@ use crate::subscriptions::Subscriptions;
 use jsonrpc_derive::rpc;
 use jsonrpc_pubsub::{typed::Subscriber, SubscriptionId};
 use log::warn;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use primitives::{Bytes, Blake2Hasher, H256};
 use sr_primitives::{generic, traits};
 use self::error::Result;
@@ -110,7 +110,7 @@ impl<B, E, P, RA> AuthorApi<ExHash<P>, BlockHash<P>> for Author<B, E, P, RA> whe
 	type Metadata = crate::metadata::Metadata;
 
 	fn submit_extrinsic(&self, ext: Bytes) -> Result<ExHash<P>> {
-		let xt = Decode::decode(&mut &ext[..]).ok_or(error::Error::BadFormat)?;
+		let xt = Decode::decode(&mut &ext[..])?;
 		let best_block_hash = self.client.info().chain.best_hash;
 		self.pool
 			.submit_one(&generic::BlockId::hash(best_block_hash), xt)
@@ -129,7 +129,7 @@ impl<B, E, P, RA> AuthorApi<ExHash<P>, BlockHash<P>> for Author<B, E, P, RA> whe
 			.map(|x| match x {
 				hash::ExtrinsicOrHash::Hash(h) => Ok(h),
 				hash::ExtrinsicOrHash::Extrinsic(bytes) => {
-					let xt = Decode::decode(&mut &bytes[..]).ok_or(error::Error::BadFormat)?;
+					let xt = Decode::decode(&mut &bytes[..])?;
 					Ok(self.pool.hash_of(&xt))
 				},
 			})
@@ -146,8 +146,7 @@ impl<B, E, P, RA> AuthorApi<ExHash<P>, BlockHash<P>> for Author<B, E, P, RA> whe
 	fn watch_extrinsic(&self, _metadata: Self::Metadata, subscriber: Subscriber<Status<ExHash<P>, BlockHash<P>>>, xt: Bytes) {
 		let submit = || -> Result<_> {
 			let best_block_hash = self.client.info().chain.best_hash;
-			let dxt = <<P as PoolChainApi>::Block as traits::Block>::Extrinsic::decode(&mut &xt[..])
-				.ok_or(error::Error::BadFormat)?;
+			let dxt = <<P as PoolChainApi>::Block as traits::Block>::Extrinsic::decode(&mut &xt[..])?;
 			self.pool
 				.submit_and_watch(&generic::BlockId::hash(best_block_hash), dxt)
 				.map_err(|e| e.into_pool_error()
diff --git a/substrate/core/rpc/src/author/tests.rs b/substrate/core/rpc/src/author/tests.rs
index cf320ee144..6295220820 100644
--- a/substrate/core/rpc/src/author/tests.rs
+++ b/substrate/core/rpc/src/author/tests.rs
@@ -18,7 +18,7 @@ use super::*;
 
 use std::sync::Arc;
 use assert_matches::assert_matches;
-use parity_codec::Encode;
+use codec::Encode;
 use transaction_pool::{
 	txpool::Pool,
 	ChainApi,
diff --git a/substrate/core/service/Cargo.toml b/substrate/core/service/Cargo.toml
index 4ce3facb52..dcb47bbbfb 100644
--- a/substrate/core/service/Cargo.toml
+++ b/substrate/core/service/Cargo.toml
@@ -27,7 +27,7 @@ consensus_common = { package = "substrate-consensus-common", path = "../../core/
 network = { package = "substrate-network", path = "../../core/network" }
 client = { package = "substrate-client", path = "../../core/client" }
 client_db = { package = "substrate-client-db", path = "../../core/client/db", features = ["kvdb-rocksdb"] }
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 substrate-executor = { path = "../../core/executor" }
 transaction_pool = { package = "substrate-transaction-pool", path = "../../core/transaction-pool" }
 rpc = { package = "substrate-rpc-servers", path = "../../core/rpc-servers" }
diff --git a/substrate/core/service/src/chain_ops.rs b/substrate/core/service/src/chain_ops.rs
index 19666c090c..c977b265bb 100644
--- a/substrate/core/service/src/chain_ops.rs
+++ b/substrate/core/service/src/chain_ops.rs
@@ -16,7 +16,7 @@
 
 //! Chain utilities.
 
-use std::{self, io::{Read, Write}};
+use std::{self, io::{Read, Write, Seek}};
 use futures::prelude::*;
 use futures03::TryFutureExt as _;
 use log::{info, warn};
@@ -29,7 +29,7 @@ use network::message;
 use consensus_common::BlockOrigin;
 use crate::components::{self, Components, ServiceFactory, FactoryFullConfiguration, FactoryBlockNumber, RuntimeGenesis};
 use crate::new_client;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode, IoReader};
 use crate::error;
 use crate::chain_spec::ChainSpec;
 
@@ -136,9 +136,9 @@ impl<B: Block> Link<B> for WaitLink {
 pub fn import_blocks<F, E, R>(
 	mut config: FactoryFullConfiguration<F>,
 	exit: E,
-	mut input: R
+	input: R
 ) -> error::Result<impl Future<Item = (), Error = ()>>
-	where F: ServiceFactory, E: Future<Item=(),Error=()> + Send + 'static, R: Read,
+	where F: ServiceFactory, E: Future<Item=(),Error=()> + Send + 'static, R: Read + Seek,
 {
 	let client = new_client::<F>(&config)?;
 	// FIXME #1134 this shouldn't need a mutable config.
@@ -155,37 +155,42 @@ pub fn import_blocks<F, E, R>(
 		let _ = exit_send.send(());
 	});
 
-	let count: u64 = Decode::decode(&mut input).ok_or("Error reading file")?;
+	let mut io_reader_input = IoReader(input);
+	let count: u64 = Decode::decode(&mut io_reader_input)
+		.map_err(|e| format!("Error reading file: {}", e))?;
 	info!("Importing {} blocks", count);
 	let mut block_count = 0;
 	for b in 0 .. count {
 		if exit_recv.try_recv().is_ok() {
 			break;
 		}
-		if let Some(signed) = SignedBlock::<F::Block>::decode(&mut input) {
-			let (header, extrinsics) = signed.block.deconstruct();
-			let hash = header.hash();
-			let block  = message::BlockData::<F::Block> {
-				hash,
-				justification: signed.justification,
-				header: Some(header),
-				body: Some(extrinsics),
-				receipt: None,
-				message_queue: None
-			};
-			// import queue handles verification and importing it into the client
-			queue.import_blocks(BlockOrigin::File, vec![
-				IncomingBlock::<F::Block>{
-					hash: block.hash,
-					header: block.header,
-					body: block.body,
-					justification: block.justification,
-					origin: None,
-				}
-			]);
-		} else {
-			warn!("Error reading block data at {}.", b);
-			break;
+		match SignedBlock::<F::Block>::decode(&mut io_reader_input) {
+			Ok(signed) => {
+				let (header, extrinsics) = signed.block.deconstruct();
+				let hash = header.hash();
+				let block  = message::BlockData::<F::Block> {
+					hash,
+					justification: signed.justification,
+					header: Some(header),
+					body: Some(extrinsics),
+					receipt: None,
+					message_queue: None
+				};
+				// import queue handles verification and importing it into the client
+				queue.import_blocks(BlockOrigin::File, vec![
+					IncomingBlock::<F::Block> {
+						hash: block.hash,
+						header: block.header,
+						body: block.body,
+						justification: block.justification,
+						origin: None,
+					}
+				]);
+			}
+			Err(e) => {
+				warn!("Error reading block data at {}: {}", b, e);
+				break;
+			}
 		}
 
 		block_count = b;
diff --git a/substrate/core/service/src/lib.rs b/substrate/core/service/src/lib.rs
index cd904156c5..bcb5cfa3b8 100644
--- a/substrate/core/service/src/lib.rs
+++ b/substrate/core/service/src/lib.rs
@@ -40,7 +40,7 @@ use futures03::stream::{StreamExt as _, TryStreamExt as _};
 use keystore::Store as Keystore;
 use network::{NetworkState, NetworkStateInfo};
 use log::{log, info, warn, debug, error, Level};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use primitives::{Pair, ed25519, sr25519, crypto};
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{Header, NumberFor, SaturatedConversion, Zero};
@@ -877,28 +877,31 @@ impl<C: Components> network::TransactionPool<ComponentExHash<C>, ComponentBlock<
 		}
 
 		let encoded = transaction.encode();
-		if let Some(uxt) = Decode::decode(&mut &encoded[..]) {
-			let best_block_id = self.best_block_id()?;
-			match self.pool.submit_one(&best_block_id, uxt) {
-				Ok(hash) => Some(hash),
-				Err(e) => match e.into_pool_error() {
-					Ok(txpool::error::Error::AlreadyImported(hash)) => {
-						hash.downcast::<ComponentExHash<C>>().ok()
-							.map(|x| x.as_ref().clone())
-					},
-					Ok(e) => {
-						debug!("Error adding transaction to the pool: {:?}", e);
-						None
-					},
-					Err(e) => {
-						debug!("Error converting pool error: {:?}", e);
-						None
-					},
+		match Decode::decode(&mut &encoded[..]) {
+			Ok(uxt) => {
+				let best_block_id = self.best_block_id()?;
+				match self.pool.submit_one(&best_block_id, uxt) {
+					Ok(hash) => Some(hash),
+					Err(e) => match e.into_pool_error() {
+						Ok(txpool::error::Error::AlreadyImported(hash)) => {
+							hash.downcast::<ComponentExHash<C>>().ok()
+								.map(|x| x.as_ref().clone())
+						},
+						Ok(e) => {
+							debug!("Error adding transaction to the pool: {:?}", e);
+							None
+						},
+						Err(e) => {
+							debug!("Error converting pool error: {:?}", e);
+							None
+						},
+					}
 				}
 			}
-		} else {
-			debug!("Error decoding transaction");
-			None
+			Err(e) => {
+				debug!("Error decoding transaction {}", e);
+				None
+			}
 		}
 	}
 
diff --git a/substrate/core/sr-api-macros/Cargo.toml b/substrate/core/sr-api-macros/Cargo.toml
index aed1c022da..3301b2fdc7 100644
--- a/substrate/core/sr-api-macros/Cargo.toml
+++ b/substrate/core/sr-api-macros/Cargo.toml
@@ -23,7 +23,7 @@ sr-version = { path = "../sr-version" }
 primitives = { package = "substrate-primitives",  path = "../primitives" }
 criterion = "0.2"
 consensus_common = { package = "substrate-consensus-common", path = "../consensus/common" }
-codec = { package = "parity-codec", version = "4.1.1" }
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 trybuild = "1.0"
 
 [[bench]]
diff --git a/substrate/core/sr-api-macros/src/decl_runtime_apis.rs b/substrate/core/sr-api-macros/src/decl_runtime_apis.rs
index c2501220b6..27f102740b 100644
--- a/substrate/core/sr-api-macros/src/decl_runtime_apis.rs
+++ b/substrate/core/sr-api-macros/src/decl_runtime_apis.rs
@@ -192,7 +192,7 @@ fn generate_native_call_generators(decl: &ItemTrait) -> Result<TokenStream> {
 		{
 			<R as #crate_::runtime_api::Decode>::decode(
 				&mut &#crate_::runtime_api::Encode::encode(input)[..]
-			).ok_or_else(|| error_desc)
+			).map_err(|_| error_desc)
 		}
 	));
 
@@ -682,9 +682,9 @@ impl<'a> ToClientSideDecl<'a> {
 								},
 								#crate_::runtime_api::NativeOrEncoded::Encoded(r) => {
 									<#ret_type as #crate_::runtime_api::Decode>::decode(&mut &r[..])
-										.ok_or_else(||
+										.map_err(|err|
 											#crate_::error::Error::CallResultDecode(
-												#function_name
+												#function_name, err
 											).into()
 										)
 								}
diff --git a/substrate/core/sr-api-macros/src/impl_runtime_apis.rs b/substrate/core/sr-api-macros/src/impl_runtime_apis.rs
index 530405068a..973fa0558a 100644
--- a/substrate/core/sr-api-macros/src/impl_runtime_apis.rs
+++ b/substrate/core/sr-api-macros/src/impl_runtime_apis.rs
@@ -77,8 +77,8 @@ fn generate_impl_call(
 		quote!(
 			#(
 				let #pnames : #ptypes = match #c_iter::runtime_api::Decode::decode(&mut #input) {
-					Some(input) => input,
-					None => panic!("Bad input data provided to {}", #fn_name_str),
+					Ok(input) => input,
+					Err(e) => panic!("Bad input data provided to {}: {}", #fn_name_str, e.what()),
 				};
 			)*
 
diff --git a/substrate/core/sr-io/Cargo.toml b/substrate/core/sr-io/Cargo.toml
index a103245721..0e6fba5bd7 100644
--- a/substrate/core/sr-io/Cargo.toml
+++ b/substrate/core/sr-io/Cargo.toml
@@ -11,7 +11,7 @@ rustc_version = "0.2"
 [dependencies]
 rstd = { package = "sr-std", path = "../sr-std", default-features = false }
 primitives = { package = "substrate-primitives", path = "../primitives", default-features = false }
-codec = { package = "parity-codec", version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 hash-db = { version = "0.15.0", default-features = false }
 libsecp256k1 = { version = "0.2.1", optional = true }
 tiny-keccak = { version = "1.4.2", optional = true }
diff --git a/substrate/core/sr-io/src/lib.rs b/substrate/core/sr-io/src/lib.rs
index 7729a1e573..ac4799513d 100644
--- a/substrate/core/sr-io/src/lib.rs
+++ b/substrate/core/sr-io/src/lib.rs
@@ -324,7 +324,7 @@ export_api! {
 
 		/// Initiates a http request given HTTP verb and the URL.
 		///
-		/// Meta is a future-reserved field containing additional, parity-codec encoded parameters.
+		/// Meta is a future-reserved field containing additional, parity-scale-codec encoded parameters.
 		/// Returns the id of newly started request.
 		fn http_request_start(
 			method: &str,
diff --git a/substrate/core/sr-io/without_std.rs b/substrate/core/sr-io/without_std.rs
index 861f94ced5..4dc28f0471 100644
--- a/substrate/core/sr-io/without_std.rs
+++ b/substrate/core/sr-io/without_std.rs
@@ -529,7 +529,7 @@ pub mod ext {
 
 		/// Initiates a http request.
 		///
-		/// `meta` is parity-codec encoded additional parameters to the request (like redirection policy,
+		/// `meta` is parity-scale-codec encoded additional parameters to the request (like redirection policy,
 		/// timeouts, certificates policy, etc). The format is not yet specified and the field is currently
 		/// only reserved for future use.
 		///
@@ -596,7 +596,7 @@ pub mod ext {
 		///
 		/// # Returns
 		///
-		/// - A pointer to parity-codec encoded vector of pairs `(HeaderKey, HeaderValue)`.
+		/// - A pointer to parity-scale-codec encoded vector of pairs `(HeaderKey, HeaderValue)`.
 		/// - In case invalid `id` is passed it returns a pointer to parity-encoded empty vector.
 		fn ext_http_response_headers(
 			id: u32,
diff --git a/substrate/core/sr-primitives/Cargo.toml b/substrate/core/sr-primitives/Cargo.toml
index f736df0e01..e161d5b887 100644
--- a/substrate/core/sr-primitives/Cargo.toml
+++ b/substrate/core/sr-primitives/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2018"
 num-traits = { version = "0.2", default-features = false }
 integer-sqrt = { version = "0.1.2" }
 serde = { version = "1.0", optional = true, features = ["derive"] }
-codec = { package = "parity-codec", version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives",  path = "../primitives", default-features = false }
 rstd = { package = "sr-std", path = "../sr-std", default-features = false }
 runtime_io = { package = "sr-io", path = "../sr-io", default-features = false }
@@ -17,7 +17,7 @@ paste = { version = "0.1"}
 
 [dev-dependencies]
 serde_json = "1.0"
-primitive-types = "0.4"
+primitive-types = "0.5.0"
 
 [features]
 default = ["std"]
diff --git a/substrate/core/sr-primitives/src/generic/digest.rs b/substrate/core/sr-primitives/src/generic/digest.rs
index 9d18f67f4c..b6d72dddf7 100644
--- a/substrate/core/sr-primitives/src/generic/digest.rs
+++ b/substrate/core/sr-primitives/src/generic/digest.rs
@@ -22,7 +22,7 @@ use serde::Serialize;
 use rstd::prelude::*;
 
 use crate::ConsensusEngineId;
-use crate::codec::{Decode, Encode, Input};
+use crate::codec::{Decode, Encode, Input, Error};
 
 /// Generic header digest.
 #[derive(PartialEq, Eq, Clone, Encode, Decode)]
@@ -221,27 +221,29 @@ impl<Hash: Encode> Encode for DigestItem<Hash> {
 	}
 }
 
+impl<Hash: Encode> codec::EncodeLike for DigestItem<Hash> {}
+
 impl<Hash: Decode> Decode for DigestItem<Hash> {
 	#[allow(deprecated)]
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
 		let item_type: DigestItemType = Decode::decode(input)?;
 		match item_type {
-			DigestItemType::ChangesTrieRoot => Some(DigestItem::ChangesTrieRoot(
+			DigestItemType::ChangesTrieRoot => Ok(DigestItem::ChangesTrieRoot(
 				Decode::decode(input)?,
 			)),
 			DigestItemType::PreRuntime => {
 				let vals: (ConsensusEngineId, Vec<u8>) = Decode::decode(input)?;
-				Some(DigestItem::PreRuntime(vals.0, vals.1))
+				Ok(DigestItem::PreRuntime(vals.0, vals.1))
 			},
 			DigestItemType::Consensus => {
 				let vals: (ConsensusEngineId, Vec<u8>) = Decode::decode(input)?;
-				Some(DigestItem::Consensus(vals.0, vals.1))
+				Ok(DigestItem::Consensus(vals.0, vals.1))
 			}
 			DigestItemType::Seal => {
 				let vals: (ConsensusEngineId, Vec<u8>) = Decode::decode(input)?;
-				Some(DigestItem::Seal(vals.0, vals.1))
+				Ok(DigestItem::Seal(vals.0, vals.1))
 			},
-			DigestItemType::Other => Some(DigestItem::Other(
+			DigestItemType::Other => Ok(DigestItem::Other(
 				Decode::decode(input)?,
 			)),
 		}
@@ -305,7 +307,7 @@ impl<'a, Hash> DigestItemRef<'a, Hash> {
 	/// Try to match this digest item to the given opaque item identifier; if it matches, then
 	/// try to cast to the given datatype; if that works, return it.
 	pub fn try_to<T: Decode>(&self, id: OpaqueDigestItemId) -> Option<T> {
-		self.try_as_raw(id).and_then(|mut x| Decode::decode(&mut x))
+		self.try_as_raw(id).and_then(|mut x| Decode::decode(&mut x).ok())
 	}
 }
 
@@ -340,6 +342,8 @@ impl<'a, Hash: Encode> Encode for DigestItemRef<'a, Hash> {
 	}
 }
 
+impl<'a, Hash: Encode> codec::EncodeLike for DigestItemRef<'a, Hash> {}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
diff --git a/substrate/core/sr-primitives/src/generic/era.rs b/substrate/core/sr-primitives/src/generic/era.rs
index c41d3eedfc..7308a8adc5 100644
--- a/substrate/core/sr-primitives/src/generic/era.rs
+++ b/substrate/core/sr-primitives/src/generic/era.rs
@@ -19,7 +19,7 @@
 #[cfg(feature = "std")]
 use serde::{Serialize, Deserialize};
 
-use crate::codec::{Decode, Encode, Input, Output};
+use crate::codec::{Decode, Encode, Input, Output, Error};
 
 /// Era period
 pub type Period = u64;
@@ -111,20 +111,22 @@ impl Encode for Era {
 	}
 }
 
+impl codec::EncodeLike for Era {}
+
 impl Decode for Era {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
 		let first = input.read_byte()?;
 		if first == 0 {
-			Some(Era::Immortal)
+			Ok(Era::Immortal)
 		} else {
 			let encoded = first as u64 + ((input.read_byte()? as u64) << 8);
 			let period = 2 << (encoded % (1 << 4));
 			let quantize_factor = (period >> 12).max(1);
 			let phase = (encoded >> 4) * quantize_factor;
 			if period >= 4 && phase < period {
-				Some(Era::Mortal(period, phase))
+				Ok(Era::Mortal(period, phase))
 			} else {
-				None
+				Err("Invalid period and phase".into())
 			}
 		}
 	}
diff --git a/substrate/core/sr-primitives/src/generic/header.rs b/substrate/core/sr-primitives/src/generic/header.rs
index 66d226b2c4..e8f40bb7b6 100644
--- a/substrate/core/sr-primitives/src/generic/header.rs
+++ b/substrate/core/sr-primitives/src/generic/header.rs
@@ -20,7 +20,7 @@
 use serde::Serialize;
 #[cfg(feature = "std")]
 use log::debug;
-use crate::codec::{Decode, Encode, Codec, Input, Output, HasCompact, EncodeAsRef};
+use crate::codec::{Decode, Encode, Codec, Input, Output, HasCompact, EncodeAsRef, Error};
 use crate::traits::{
 	self, Member, SimpleArithmetic, SimpleBitOps, MaybeDisplay, Hash as HashT, MaybeSerializeDebug,
 	MaybeSerializeDebugButNotDeserialize
@@ -60,8 +60,8 @@ impl<Number, Hash> Decode for Header<Number, Hash> where
 	Hash: HashT,
 	Hash::Output: Decode,
 {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
-		Some(Header {
+	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
+		Ok(Header {
 			parent_hash: Decode::decode(input)?,
 			number: <<Number as HasCompact>::Type>::decode(input)?.into(),
 			state_root: Decode::decode(input)?,
@@ -85,6 +85,12 @@ impl<Number, Hash> Encode for Header<Number, Hash> where
 	}
 }
 
+impl<Number, Hash> codec::EncodeLike for Header<Number, Hash> where
+	Number: HasCompact + Copy + Into<u128>,
+	Hash: HashT,
+	Hash::Output: Encode,
+{}
+
 impl<Number, Hash> traits::Header for Header<Number, Hash> where
 	Number: Member + MaybeSerializeDebug + ::rstd::hash::Hash + MaybeDisplay + SimpleArithmetic + Codec + Copy + Into<u128>,
 	Hash: HashT,
diff --git a/substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs b/substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs
index b803a20397..d87c9e045f 100644
--- a/substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs
+++ b/substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs
@@ -21,7 +21,7 @@ use std::fmt;
 
 use rstd::prelude::*;
 use runtime_io::blake2_256;
-use crate::codec::{Decode, Encode, Input};
+use crate::codec::{Decode, Encode, Input, Error};
 use crate::traits::{self, Member, MaybeDisplay, SignedExtension, Checkable, Extrinsic};
 use super::CheckedExtrinsic;
 
@@ -131,7 +131,7 @@ where
 	Call: Decode,
 	Extra: SignedExtension,
 {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
 		// This is a little more complicated than usual since the binary format must be compatible
 		// with substrate's generic `Vec<u8>` type. Basically this just means accepting that there
 		// will be a prefix of vector length (we don't need
@@ -143,10 +143,10 @@ where
 		let is_signed = version & 0b1000_0000 != 0;
 		let version = version & 0b0111_1111;
 		if version != TRANSACTION_VERSION {
-			return None
+			return Err("Invalid transaction version".into());
 		}
 
-		Some(UncheckedExtrinsic {
+		Ok(UncheckedExtrinsic {
 			signature: if is_signed { Some(Decode::decode(input)?) } else { None },
 			function: Decode::decode(input)?,
 		})
@@ -245,7 +245,7 @@ mod tests {
 	fn unsigned_codec_should_work() {
 		let ux = Ex::new_unsigned(vec![0u8; 0]);
 		let encoded = ux.encode();
-		assert_eq!(Ex::decode(&mut &encoded[..]), Some(ux));
+		assert_eq!(Ex::decode(&mut &encoded[..]), Ok(ux));
 	}
 
 	#[test]
@@ -257,7 +257,7 @@ mod tests {
 			TestExtra
 		);
 		let encoded = ux.encode();
-		assert_eq!(Ex::decode(&mut &encoded[..]), Some(ux));
+		assert_eq!(Ex::decode(&mut &encoded[..]), Ok(ux));
 	}
 
 	#[test]
@@ -270,7 +270,7 @@ mod tests {
 			TestExtra
 		);
 		let encoded = ux.encode();
-		assert_eq!(Ex::decode(&mut &encoded[..]), Some(ux));
+		assert_eq!(Ex::decode(&mut &encoded[..]), Ok(ux));
 	}
 
 	#[test]
diff --git a/substrate/core/sr-primitives/src/lib.rs b/substrate/core/sr-primitives/src/lib.rs
index 08cd4d1a05..1c9def98c1 100644
--- a/substrate/core/sr-primitives/src/lib.rs
+++ b/substrate/core/sr-primitives/src/lib.rs
@@ -694,6 +694,8 @@ impl codec::Encode for ApplyOutcome {
 	}
 }
 
+impl codec::EncodeLike for ApplyOutcome {}
+
 #[derive(Eq, PartialEq, Clone, Copy, Decode)]
 #[cfg_attr(feature = "std", derive(Debug, Serialize))]
 #[repr(u8)]
@@ -717,6 +719,8 @@ impl codec::Encode for ApplyError {
 	}
 }
 
+impl codec::EncodeLike for ApplyError {}
+
 /// Result from attempt to apply an extrinsic.
 pub type ApplyResult = Result<ApplyOutcome, ApplyError>;
 
diff --git a/substrate/core/sr-primitives/src/testing.rs b/substrate/core/sr-primitives/src/testing.rs
index 0986c4f81a..3d55e9c4b9 100644
--- a/substrate/core/sr-primitives/src/testing.rs
+++ b/substrate/core/sr-primitives/src/testing.rs
@@ -70,7 +70,9 @@ impl OpaqueKeys for UintAuthorityId {
 			)
 		}
 	}
-	fn get<T: Decode>(&self, _: KeyTypeId) -> Option<T> { self.0.using_encoded(|mut x| T::decode(&mut x)) }
+	fn get<T: Decode>(&self, _: KeyTypeId) -> Option<T> {
+		self.0.using_encoded(|mut x| T::decode(&mut x)).ok()
+	}
 }
 
 /// Digest item
@@ -136,7 +138,8 @@ impl traits::Header for Header {
 impl<'a> Deserialize<'a> for Header {
 	fn deserialize<D: Deserializer<'a>>(de: D) -> Result<Self, D::Error> {
 		let r = <Vec<u8>>::deserialize(de)?;
-		Decode::decode(&mut &r[..]).ok_or(DeError::custom("Invalid value passed into decode"))
+		Decode::decode(&mut &r[..])
+			.map_err(|e| DeError::custom(format!("Invalid value passed into decode: {}", e.what())))
 	}
 }
 
@@ -204,7 +207,8 @@ impl<Xt: 'static + Codec + Sized + Send + Sync + Serialize + Clone + Eq + Debug
 impl<'a, Xt> Deserialize<'a> for Block<Xt> where Block<Xt>: Decode {
 	fn deserialize<D: Deserializer<'a>>(de: D) -> Result<Self, D::Error> {
 		let r = <Vec<u8>>::deserialize(de)?;
-		Decode::decode(&mut &r[..]).ok_or(DeError::custom("Invalid value passed into decode"))
+		Decode::decode(&mut &r[..])
+			.map_err(|e| DeError::custom(format!("Invalid value passed into decode: {}", e.what())))
 	}
 }
 
diff --git a/substrate/core/sr-primitives/src/traits.rs b/substrate/core/sr-primitives/src/traits.rs
index f7d55dda79..ce67a888bc 100644
--- a/substrate/core/sr-primitives/src/traits.rs
+++ b/substrate/core/sr-primitives/src/traits.rs
@@ -1029,21 +1029,30 @@ pub trait OpaqueKeys: Clone {
 	/// Get the raw bytes of key with key-type ID `i`.
 	fn get_raw(&self, i: super::KeyTypeId) -> &[u8];
 	/// Get the decoded key with index `i`.
-	fn get<T: Decode>(&self, i: super::KeyTypeId) -> Option<T> { T::decode(&mut self.get_raw(i)) }
+	fn get<T: Decode>(&self, i: super::KeyTypeId) -> Option<T> {
+		T::decode(&mut self.get_raw(i)).ok()
+	}
 	/// Verify a proof of ownership for the keys.
 	fn ownership_proof_is_valid(&self, _proof: &[u8]) -> bool { true }
 }
 
+/// Input that adds infinite number of zero after wrapped input.
 struct TrailingZeroInput<'a>(&'a [u8]);
+
 impl<'a> codec::Input for TrailingZeroInput<'a> {
-	fn read(&mut self, into: &mut [u8]) -> usize {
-		let len = into.len().min(self.0.len());
-		into[..len].copy_from_slice(&self.0[..len]);
-		for i in &mut into[len..] {
+	fn remaining_len(&mut self) -> Result<Option<usize>, codec::Error> {
+		Ok(None)
+	}
+
+	fn read(&mut self, into: &mut [u8]) -> Result<(), codec::Error> {
+		let len_from_inner = into.len().min(self.0.len());
+		into[..len_from_inner].copy_from_slice(&self.0[..len_from_inner]);
+		for i in &mut into[len_from_inner..] {
 			*i = 0;
 		}
-		self.0 = &self.0[len..];
-		into.len()
+		self.0 = &self.0[len_from_inner..];
+
+		Ok(())
 	}
 }
 
@@ -1091,7 +1100,7 @@ impl<T: Encode + Decode + Default, Id: Encode + Decode + TypeId> AccountIdConver
 		x.using_encoded(|d| {
 			if &d[0..4] != Id::TYPE_ID { return None }
 			let mut cursor = &d[4..];
-			let result = Decode::decode(&mut cursor)?;
+			let result = Decode::decode(&mut cursor).ok()?;
 			if cursor.iter().all(|x| *x == 0) {
 				Some(result)
 			} else {
@@ -1104,7 +1113,7 @@ impl<T: Encode + Decode + Default, Id: Encode + Decode + TypeId> AccountIdConver
 #[cfg(test)]
 mod tests {
 	use super::AccountIdConversion;
-	use crate::codec::{Encode, Decode};
+	use crate::codec::{Encode, Decode, Input};
 
 	#[derive(Encode, Decode, Default, PartialEq, Debug)]
 	struct U32Value(u32);
@@ -1153,6 +1162,22 @@ mod tests {
 		let r = U16Value::try_from_account(&0x0100_c0da_f00dcafe_u64);
 		assert!(r.is_none());
 	}
+
+	#[test]
+	fn trailing_zero_should_work() {
+		let mut t = super::TrailingZeroInput(&[1, 2, 3]);
+		assert_eq!(t.remaining_len(), Ok(None));
+		let mut buffer = [0u8; 2];
+		assert_eq!(t.read(&mut buffer), Ok(()));
+		assert_eq!(t.remaining_len(), Ok(None));
+		assert_eq!(buffer, [1, 2]);
+		assert_eq!(t.read(&mut buffer), Ok(()));
+		assert_eq!(t.remaining_len(), Ok(None));
+		assert_eq!(buffer, [3, 0]);
+		assert_eq!(t.read(&mut buffer), Ok(()));
+		assert_eq!(t.remaining_len(), Ok(None));
+		assert_eq!(buffer, [0, 0]);
+	}
 }
 
 /// Calls a given macro a number of times with a set of fixed params and an incrementing numeral.
diff --git a/substrate/core/sr-primitives/src/transaction_validity.rs b/substrate/core/sr-primitives/src/transaction_validity.rs
index a6cc43c5a3..4d5d53baf1 100644
--- a/substrate/core/sr-primitives/src/transaction_validity.rs
+++ b/substrate/core/sr-primitives/src/transaction_validity.rs
@@ -17,7 +17,7 @@
 //! Transaction validity interface.
 
 use rstd::prelude::*;
-use crate::codec::{Encode, Decode};
+use crate::codec::{Encode, Decode, Error};
 use crate::traits::DispatchError;
 
 /// Priority for a transaction. Additive. Higher is better.
@@ -113,9 +113,9 @@ impl ValidTransaction {
 }
 
 impl Decode for TransactionValidity {
-	fn decode<I: crate::codec::Input>(value: &mut I) -> Option<Self> {
+	fn decode<I: crate::codec::Input>(value: &mut I) -> Result<Self, Error> {
 		match value.read_byte()? {
-			0 => Some(TransactionValidity::Invalid(i8::decode(value)?)),
+			0 => Ok(TransactionValidity::Invalid(i8::decode(value)?)),
 			1 => {
 				let priority = TransactionPriority::decode(value)?;
 				let requires = Vec::decode(value)?;
@@ -123,12 +123,12 @@ impl Decode for TransactionValidity {
 				let longevity = TransactionLongevity::decode(value)?;
 				let propagate = bool::decode(value).unwrap_or(true);
 
-				Some(TransactionValidity::Valid(ValidTransaction {
+				Ok(TransactionValidity::Valid(ValidTransaction {
 					priority, requires, provides, longevity, propagate,
 				}))
 			},
-			2 => Some(TransactionValidity::Unknown(i8::decode(value)?)),
-			_ => None,
+			2 => Ok(TransactionValidity::Unknown(i8::decode(value)?)),
+			_ => Err("Invalid transaction validity variant".into()),
 		}
 	}
 }
@@ -143,7 +143,7 @@ mod tests {
 			1, 5, 0, 0, 0, 0, 0, 0, 0, 4, 16, 1, 2, 3, 4, 4, 12, 4, 5, 6, 42, 0, 0, 0, 0, 0, 0, 0
 		];
 
-		assert_eq!(TransactionValidity::decode(&mut &*old_encoding), Some(TransactionValidity::Valid(ValidTransaction {
+		assert_eq!(TransactionValidity::decode(&mut &*old_encoding), Ok(TransactionValidity::Valid(ValidTransaction {
 			priority: 5,
 			requires: vec![vec![1, 2, 3, 4]],
 			provides: vec![vec![4, 5, 6]],
@@ -169,6 +169,6 @@ mod tests {
 		);
 
 		// decode back
-		assert_eq!(TransactionValidity::decode(&mut &*encoded), Some(v));
+		assert_eq!(TransactionValidity::decode(&mut &*encoded), Ok(v));
 	}
 }
diff --git a/substrate/core/sr-sandbox/Cargo.toml b/substrate/core/sr-sandbox/Cargo.toml
index 5e3aabfd23..da80b2f213 100755
--- a/substrate/core/sr-sandbox/Cargo.toml
+++ b/substrate/core/sr-sandbox/Cargo.toml
@@ -12,7 +12,7 @@ rustc_version = "0.2"
 wasmi = { version = "0.5.0", optional = true }
 primitives = { package = "substrate-primitives", path = "../primitives", default-features = false }
 rstd = { package = "sr-std", path = "../sr-std", default-features = false }
-codec = { package = "parity-codec", version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 
 [dev-dependencies]
 wabt = "~0.7.4"
diff --git a/substrate/core/sr-sandbox/without_std.rs b/substrate/core/sr-sandbox/without_std.rs
index 9fb255a523..ee5f7697fe 100755
--- a/substrate/core/sr-sandbox/without_std.rs
+++ b/substrate/core/sr-sandbox/without_std.rs
@@ -304,7 +304,7 @@ impl<T> Instance<T> {
 		match result {
 			sandbox_primitives::ERR_OK => {
 				let return_val = sandbox_primitives::ReturnValue::decode(&mut &return_val[..])
-					.ok_or(Error::Execution)?;
+					.map_err(|_| Error::Execution)?;
 				Ok(return_val)
 			}
 			sandbox_primitives::ERR_EXECUTION => Err(Error::Execution),
diff --git a/substrate/core/sr-version/Cargo.toml b/substrate/core/sr-version/Cargo.toml
index e7ce3327a0..a83d1f6415 100644
--- a/substrate/core/sr-version/Cargo.toml
+++ b/substrate/core/sr-version/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 impl-serde = { version = "0.1", optional = true }
 serde = { version = "1.0", optional = true, features = ["derive"] }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../sr-std", default-features = false }
 sr-primitives = {  path = "../sr-primitives", default-features = false }
 
@@ -16,7 +16,7 @@ default = ["std"]
 std = [
 	"impl-serde",
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"sr-primitives/std",
 ]
diff --git a/substrate/core/sr-version/src/lib.rs b/substrate/core/sr-version/src/lib.rs
index 12998cecbc..cf96fe70e2 100644
--- a/substrate/core/sr-version/src/lib.rs
+++ b/substrate/core/sr-version/src/lib.rs
@@ -27,9 +27,9 @@ use std::collections::HashSet;
 #[cfg(feature = "std")]
 use sr_primitives::traits::RuntimeApiInfo;
 
-use parity_codec::Encode;
+use codec::Encode;
 #[cfg(feature = "std")]
-use parity_codec::Decode;
+use codec::Decode;
 use sr_primitives::RuntimeString;
 pub use sr_primitives::create_runtime_str;
 
diff --git a/substrate/core/state-db/Cargo.toml b/substrate/core/state-db/Cargo.toml
index a8dad1e84e..55d66ea5f8 100644
--- a/substrate/core/state-db/Cargo.toml
+++ b/substrate/core/state-db/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2018"
 parking_lot = "0.8.0"
 log = "0.4"
 primitives = { package = "substrate-primitives", path = "../../core/primitives" }
-parity-codec = { version = "4.1.1", features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
 
 [dev-dependencies]
 env_logger = "0.6"
diff --git a/substrate/core/state-db/src/lib.rs b/substrate/core/state-db/src/lib.rs
index 4434fa4ef6..43820529d4 100644
--- a/substrate/core/state-db/src/lib.rs
+++ b/substrate/core/state-db/src/lib.rs
@@ -35,7 +35,6 @@ mod pruning;
 
 use std::fmt;
 use parking_lot::RwLock;
-use parity_codec as codec;
 use codec::Codec;
 use std::collections::{VecDeque, HashMap, hash_map::Entry};
 use noncanonical::NonCanonicalOverlay;
@@ -71,7 +70,7 @@ pub enum Error<E: fmt::Debug> {
 	/// Database backend error.
 	Db(E),
 	/// `Codec` decoding error.
-	Decoding,
+	Decoding(codec::Error),
 	/// Trying to canonicalize invalid block.
 	InvalidBlock,
 	/// Trying to insert block with invalid number.
@@ -82,11 +81,17 @@ pub enum Error<E: fmt::Debug> {
 	DiscardingPinned,
 }
 
+impl<E: fmt::Debug> From<codec::Error> for Error<E> {
+	fn from(x: codec::Error) -> Self {
+		Error::Decoding(x)
+	}
+}
+
 impl<E: fmt::Debug> fmt::Debug for Error<E> {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		match self {
 			Error::Db(e) => e.fmt(f),
-			Error::Decoding => write!(f, "Error decoding slicable value"),
+			Error::Decoding(e) => write!(f, "Error decoding slicable value: {}", e.what()),
 			Error::InvalidBlock => write!(f, "Trying to canonicalize invalid block"),
 			Error::InvalidBlockNumber => write!(f, "Trying to insert block with invalid number"),
 			Error::InvalidParent => write!(f, "Trying to insert block with unknown parent"),
diff --git a/substrate/core/state-db/src/noncanonical.rs b/substrate/core/state-db/src/noncanonical.rs
index 0d43389a0b..1017b8a211 100644
--- a/substrate/core/state-db/src/noncanonical.rs
+++ b/substrate/core/state-db/src/noncanonical.rs
@@ -23,7 +23,7 @@
 use std::fmt;
 use std::collections::{HashMap, VecDeque, hash_map::Entry};
 use super::{Error, DBValue, ChangeSet, CommitSet, MetaDb, Hash, to_meta_key};
-use crate::codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use log::trace;
 
 const NON_CANONICAL_JOURNAL: &[u8] = b"noncanonical_journal";
@@ -116,7 +116,7 @@ impl<BlockHash: Hash, Key: Hash> NonCanonicalOverlay<BlockHash, Key> {
 		let last_canonicalized = db.get_meta(&to_meta_key(LAST_CANONICAL, &()))
 			.map_err(|e| Error::Db(e))?;
 		let last_canonicalized = match last_canonicalized {
-			Some(buffer) => Some(<(BlockHash, u64)>::decode(&mut buffer.as_slice()).ok_or(Error::Decoding)?),
+			Some(buffer) => Some(<(BlockHash, u64)>::decode(&mut buffer.as_slice())?),
 			None => None,
 		};
 		let mut levels = VecDeque::new();
@@ -134,7 +134,7 @@ impl<BlockHash: Hash, Key: Hash> NonCanonicalOverlay<BlockHash, Key> {
 					let journal_key = to_journal_key(block, index);
 					match db.get_meta(&journal_key).map_err(|e| Error::Db(e))? {
 						Some(record) => {
-							let record: JournalRecord<BlockHash, Key> = Decode::decode(&mut record.as_slice()).ok_or(Error::Decoding)?;
+							let record: JournalRecord<BlockHash, Key> = Decode::decode(&mut record.as_slice())?;
 							let inserted = record.inserted.iter().map(|(k, _)| k.clone()).collect();
 							let overlay = BlockOverlay {
 								hash: record.hash.clone(),
diff --git a/substrate/core/state-db/src/pruning.rs b/substrate/core/state-db/src/pruning.rs
index 078745c7a2..21f472fe69 100644
--- a/substrate/core/state-db/src/pruning.rs
+++ b/substrate/core/state-db/src/pruning.rs
@@ -23,7 +23,7 @@
 //! The changes are journaled in the DB.
 
 use std::collections::{HashMap, HashSet, VecDeque};
-use crate::codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use crate::{CommitSet, Error, MetaDb, to_meta_key, Hash};
 use log::{trace, warn};
 
@@ -69,7 +69,7 @@ impl<BlockHash: Hash, Key: Hash> RefWindow<BlockHash, Key> {
 		let last_pruned = db.get_meta(&to_meta_key(LAST_PRUNED, &()))
 			.map_err(|e| Error::Db(e))?;
 		let pending_number: u64 = match last_pruned {
-			Some(buffer) => u64::decode(&mut buffer.as_slice()).ok_or(Error::Decoding)? + 1,
+			Some(buffer) => u64::decode(&mut buffer.as_slice())? + 1,
 			None => 0,
 		};
 		let mut block = pending_number;
@@ -86,7 +86,7 @@ impl<BlockHash: Hash, Key: Hash> RefWindow<BlockHash, Key> {
 			let journal_key = to_journal_key(block);
 			match db.get_meta(&journal_key).map_err(|e| Error::Db(e))? {
 				Some(record) => {
-					let record: JournalRecord<BlockHash, Key> = Decode::decode(&mut record.as_slice()).ok_or(Error::Decoding)?;
+					let record: JournalRecord<BlockHash, Key> = Decode::decode(&mut record.as_slice())?;
 					trace!(target: "state-db", "Pruning journal entry {} ({} inserted, {} deleted)", block, record.inserted.len(), record.deleted.len());
 					pruning.import(&record.hash, journal_key, record.inserted.into_iter(), record.deleted);
 				},
diff --git a/substrate/core/state-machine/Cargo.toml b/substrate/core/state-machine/Cargo.toml
index c7a15bf957..bb00cfcbb7 100644
--- a/substrate/core/state-machine/Cargo.toml
+++ b/substrate/core/state-machine/Cargo.toml
@@ -14,7 +14,7 @@ trie-root = "0.15.0"
 trie = { package = "substrate-trie", path = "../trie" }
 primitives = { package = "substrate-primitives", path = "../primitives" }
 panic-handler = { package = "substrate-panic-handler", path = "../panic-handler" }
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 num-traits = "0.2"
 
 [dev-dependencies]
diff --git a/substrate/core/state-machine/src/changes_trie/build.rs b/substrate/core/state-machine/src/changes_trie/build.rs
index d32d28906f..e1e3f6a808 100644
--- a/substrate/core/state-machine/src/changes_trie/build.rs
+++ b/substrate/core/state-machine/src/changes_trie/build.rs
@@ -18,7 +18,7 @@
 
 use std::collections::BTreeMap;
 use std::collections::btree_map::Entry;
-use parity_codec::Decode;
+use codec::Decode;
 use hash_db::Hasher;
 use num_traits::One;
 use crate::backend::Backend;
@@ -156,13 +156,13 @@ fn prepare_digest_input<'a, S, H, Number>(
 
 			let extrinsic_prefix = ExtrinsicIndex::key_neutral_prefix(digest_build_block.clone());
 			trie_storage.for_keys_with_prefix(&extrinsic_prefix, |key|
-				if let Some(InputKey::ExtrinsicIndex::<Number>(trie_key)) = Decode::decode(&mut &key[..]) {
+				if let Ok(InputKey::ExtrinsicIndex::<Number>(trie_key)) = Decode::decode(&mut &key[..]) {
 					insert_to_map(trie_key.key);
 				});
 
 			let digest_prefix = DigestIndex::key_neutral_prefix(digest_build_block.clone());
 			trie_storage.for_keys_with_prefix(&digest_prefix, |key|
-				if let Some(InputKey::DigestIndex::<Number>(trie_key)) = Decode::decode(&mut &key[..]) {
+				if let Ok(InputKey::DigestIndex::<Number>(trie_key)) = Decode::decode(&mut &key[..]) {
 					insert_to_map(trie_key.key);
 				});
 
@@ -173,7 +173,7 @@ fn prepare_digest_input<'a, S, H, Number>(
 
 #[cfg(test)]
 mod test {
-	use parity_codec::Encode;
+	use codec::Encode;
 	use primitives::Blake2Hasher;
 	use primitives::storage::well_known_keys::EXTRINSIC_INDEX;
 	use crate::backend::InMemory;
diff --git a/substrate/core/state-machine/src/changes_trie/changes_iterator.rs b/substrate/core/state-machine/src/changes_trie/changes_iterator.rs
index 66d09c98d4..f7342cc60f 100644
--- a/substrate/core/state-machine/src/changes_trie/changes_iterator.rs
+++ b/substrate/core/state-machine/src/changes_trie/changes_iterator.rs
@@ -19,7 +19,7 @@
 
 use std::cell::RefCell;
 use std::collections::VecDeque;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use hash_db::{HashDB, Hasher, EMPTY_PREFIX};
 use num_traits::One;
 use trie::{Recorder, MemoryDB};
@@ -249,8 +249,7 @@ impl<'a, RS, S, H, Number> DrilldownIteratorEssence<'a, RS, S, H, Number>
 					let extrinsics_key = ExtrinsicIndex { block: block.clone(), key: self.key.to_vec() }.encode();
 					let extrinsics = trie_reader(&self.storage, trie_root, &extrinsics_key);
 					if let Some(extrinsics) = extrinsics? {
-						let extrinsics: Option<ExtrinsicIndexValue> = Decode::decode(&mut &extrinsics[..]);
-						if let Some(extrinsics) = extrinsics {
+						if let Ok(extrinsics) = ExtrinsicIndexValue::decode(&mut &extrinsics[..]) {
 							self.extrinsics.extend(extrinsics.into_iter().rev().map(|e| (block.clone(), e)));
 						}
 					}
@@ -259,8 +258,7 @@ impl<'a, RS, S, H, Number> DrilldownIteratorEssence<'a, RS, S, H, Number>
 				let blocks_key = DigestIndex { block: block.clone(), key: self.key.to_vec() }.encode();
 				let blocks = trie_reader(&self.storage, trie_root, &blocks_key);
 				if let Some(blocks) = blocks? {
-					let blocks: Option<DigestIndexValue<Number>> = Decode::decode(&mut &blocks[..]);
-					if let Some(blocks) = blocks {
+					if let Ok(blocks) = <DigestIndexValue<Number>>::decode(&mut &blocks[..]) {
 						// filter level0 blocks here because we tend to use digest blocks,
 						// AND digest block changes could also include changes for out-of-range blocks
 						let begin = self.begin.clone();
diff --git a/substrate/core/state-machine/src/changes_trie/input.rs b/substrate/core/state-machine/src/changes_trie/input.rs
index ae939c028b..8da4f1a386 100644
--- a/substrate/core/state-machine/src/changes_trie/input.rs
+++ b/substrate/core/state-machine/src/changes_trie/input.rs
@@ -16,7 +16,7 @@
 
 //! Different types of changes trie input pairs.
 
-use parity_codec::{Decode, Encode, Input, Output};
+use codec::{Decode, Encode, Input, Output, Error};
 use crate::changes_trie::BlockNumber;
 
 /// Key of { changed key => set of extrinsic indices } mapping.
@@ -95,6 +95,8 @@ impl<Number: BlockNumber> Encode for ExtrinsicIndex<Number> {
 	}
 }
 
+impl<Number: BlockNumber> codec::EncodeLike for ExtrinsicIndex<Number> {}
+
 impl<Number: BlockNumber> DigestIndex<Number> {
 	pub fn key_neutral_prefix(block: Number) -> Vec<u8> {
 		let mut prefix = vec![2];
@@ -112,18 +114,20 @@ impl<Number: BlockNumber> Encode for DigestIndex<Number> {
 	}
 }
 
+impl<Number: BlockNumber> codec::EncodeLike for DigestIndex<Number> {}
+
 impl<Number: BlockNumber> Decode for InputKey<Number> {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
 		match input.read_byte()? {
-			1 => Some(InputKey::ExtrinsicIndex(ExtrinsicIndex {
+			1 => Ok(InputKey::ExtrinsicIndex(ExtrinsicIndex {
 				block: Decode::decode(input)?,
 				key: Decode::decode(input)?,
 			})),
-			2 => Some(InputKey::DigestIndex(DigestIndex {
+			2 => Ok(InputKey::DigestIndex(DigestIndex {
 				block: Decode::decode(input)?,
 				key: Decode::decode(input)?,
 			})),
-			_ => None,
+			_ => Err("Invalid input key variant".into()),
 		}
 	}
 }
diff --git a/substrate/core/state-machine/src/changes_trie/mod.rs b/substrate/core/state-machine/src/changes_trie/mod.rs
index 48ba9eac95..b29a515d74 100644
--- a/substrate/core/state-machine/src/changes_trie/mod.rs
+++ b/substrate/core/state-machine/src/changes_trie/mod.rs
@@ -49,7 +49,7 @@ pub use self::prune::{prune, oldest_non_pruned_trie};
 use hash_db::{Hasher, Prefix};
 use crate::backend::Backend;
 use num_traits::{One, Zero};
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use primitives;
 use crate::changes_trie::build::prepare_input;
 use crate::overlayed_changes::OverlayedChanges;
diff --git a/substrate/core/state-machine/src/ext.rs b/substrate/core/state-machine/src/ext.rs
index 7f0fa1de3f..8c54806dd9 100644
--- a/substrate/core/state-machine/src/ext.rs
+++ b/substrate/core/state-machine/src/ext.rs
@@ -338,7 +338,7 @@ where
 #[cfg(test)]
 mod tests {
 	use hex_literal::hex;
-	use parity_codec::Encode;
+	use codec::Encode;
 	use primitives::{Blake2Hasher};
 	use primitives::storage::well_known_keys::EXTRINSIC_INDEX;
 	use crate::backend::InMemory;
diff --git a/substrate/core/state-machine/src/lib.rs b/substrate/core/state-machine/src/lib.rs
index d2ffc23b78..b98228e9b2 100644
--- a/substrate/core/state-machine/src/lib.rs
+++ b/substrate/core/state-machine/src/lib.rs
@@ -22,7 +22,7 @@ use std::{fmt, panic::UnwindSafe, result, marker::PhantomData};
 use std::borrow::Cow;
 use log::warn;
 use hash_db::Hasher;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use primitives::{
 	storage::well_known_keys, NativeOrEncoded, NeverNativeValue, offchain,
 };
@@ -938,7 +938,7 @@ pub(crate) fn set_changes_trie_config(
 ) -> Result<(), Box<dyn Error>> {
 	let config = match config {
 		Some(v) => Some(Decode::decode(&mut &v[..])
-			.ok_or_else(|| Box::new("Failed to decode changes trie configuration".to_owned()) as Box<dyn Error>)?),
+			.map_err(|_| Box::new("Failed to decode changes trie configuration".to_owned()) as Box<dyn Error>)?),
 		None => None,
 	};
 
@@ -972,7 +972,7 @@ where
 #[cfg(test)]
 mod tests {
 	use std::collections::HashMap;
-	use parity_codec::Encode;
+	use codec::Encode;
 	use overlayed_changes::OverlayedValue;
 	use super::*;
 	use super::backend::InMemory;
diff --git a/substrate/core/state-machine/src/overlayed_changes.rs b/substrate/core/state-machine/src/overlayed_changes.rs
index 34bf8ca3c5..8c4160760b 100644
--- a/substrate/core/state-machine/src/overlayed_changes.rs
+++ b/substrate/core/state-machine/src/overlayed_changes.rs
@@ -18,7 +18,7 @@
 
 #[cfg(test)] use std::iter::FromIterator;
 use std::collections::{HashMap, BTreeSet};
-use parity_codec::Decode;
+use codec::Decode;
 use crate::changes_trie::{NO_EXTRINSIC_INDEX, Configuration as ChangesTrieConfig};
 use primitives::storage::well_known_keys::EXTRINSIC_INDEX;
 
@@ -267,7 +267,7 @@ impl OverlayedChanges {
 	/// Inserts storage entry responsible for current extrinsic index.
 	#[cfg(test)]
 	pub(crate) fn set_extrinsic_index(&mut self, extrinsic_index: u32) {
-		use parity_codec::Encode;
+		use codec::Encode;
 		self.prospective.top.insert(EXTRINSIC_INDEX.to_vec(), OverlayedValue {
 			value: Some(extrinsic_index.encode()),
 			extrinsics: None,
@@ -284,7 +284,7 @@ impl OverlayedChanges {
 		match self.changes_trie_config.is_some() {
 			true => Some(
 				self.storage(EXTRINSIC_INDEX)
-					.and_then(|idx| idx.and_then(|idx| Decode::decode(&mut &*idx)))
+					.and_then(|idx| idx.and_then(|idx| Decode::decode(&mut &*idx).ok()))
 					.unwrap_or(NO_EXTRINSIC_INDEX)),
 			false => None,
 		}
diff --git a/substrate/core/state-machine/src/testing.rs b/substrate/core/state-machine/src/testing.rs
index 73c0b38ef4..89290a59e2 100644
--- a/substrate/core/state-machine/src/testing.rs
+++ b/substrate/core/state-machine/src/testing.rs
@@ -27,7 +27,7 @@ use crate::changes_trie::{
 };
 use primitives::offchain;
 use primitives::storage::well_known_keys::{CHANGES_TRIE_CONFIG, CODE, HEAP_PAGES};
-use parity_codec::Encode;
+use codec::Encode;
 use super::{ChildStorageKey, Externalities, OverlayedChanges};
 
 const EXT_NOT_ALLOWED_TO_FAIL: &str = "Externalities not allowed to fail within runtime";
diff --git a/substrate/core/state-machine/src/trie_backend.rs b/substrate/core/state-machine/src/trie_backend.rs
index 18c1b0eeca..739044dd50 100644
--- a/substrate/core/state-machine/src/trie_backend.rs
+++ b/substrate/core/state-machine/src/trie_backend.rs
@@ -194,9 +194,8 @@ impl<S: TrieBackendStorage<H>, H: Hasher> Backend<H> for TrieBackend<S, H> where
 pub mod tests {
 	use std::collections::HashSet;
 	use primitives::{Blake2Hasher, H256};
-	use parity_codec::Encode;
-	use trie::{TrieMut, PrefixedMemoryDB};
-	use trie::trie_types::TrieDBMut;
+	use codec::Encode;
+	use trie::{TrieMut, PrefixedMemoryDB, trie_types::TrieDBMut};
 	use super::*;
 
 	fn test_db() -> (PrefixedMemoryDB<Blake2Hasher>, H256) {
diff --git a/substrate/core/test-client/Cargo.toml b/substrate/core/test-client/Cargo.toml
index bd3b0db2ce..163cc2ab14 100644
--- a/substrate/core/test-client/Cargo.toml
+++ b/substrate/core/test-client/Cargo.toml
@@ -12,7 +12,7 @@ executor = { package = "substrate-executor", path = "../executor" }
 futures-preview = "0.3.0-alpha.17"
 hash-db = "0.15.0"
 keyring = { package = "substrate-keyring", path = "../keyring" }
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 primitives = { package = "substrate-primitives", path = "../primitives" }
 sr-primitives = {  path = "../sr-primitives" }
 state_machine = { package = "substrate-state-machine", path = "../state-machine" }
diff --git a/substrate/core/test-client/src/client_ext.rs b/substrate/core/test-client/src/client_ext.rs
index a256dd8be5..b29a7db471 100644
--- a/substrate/core/test-client/src/client_ext.rs
+++ b/substrate/core/test-client/src/client_ext.rs
@@ -26,7 +26,7 @@ use sr_primitives::Justification;
 use sr_primitives::traits::{Block as BlockT};
 use sr_primitives::generic::BlockId;
 use primitives::Blake2Hasher;
-use parity_codec::alloc::collections::hash_map::HashMap;
+use codec::alloc::collections::hash_map::HashMap;
 
 /// Extension trait for a test client.
 pub trait ClientExt<Block: BlockT>: Sized {
diff --git a/substrate/core/test-runtime/Cargo.toml b/substrate/core/test-runtime/Cargo.toml
index 03ba10c5fb..03c95a5c27 100644
--- a/substrate/core/test-runtime/Cargo.toml
+++ b/substrate/core/test-runtime/Cargo.toml
@@ -8,7 +8,7 @@ build = "build.rs"
 [dependencies]
 log = { version = "0.4", optional = true }
 serde = { version = "1.0", optional = true, features = ["derive"] }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 keyring = { package = "substrate-keyring", path = "../keyring", optional = true }
 substrate-client = { path = "../client", default-features = false }
 primitives = { package = "substrate-primitives", path = "../primitives", default-features = false }
@@ -48,7 +48,7 @@ std = [
 	"serde",
 	"substrate-client/std",
 	"keyring",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"runtime_io/std",
 	"runtime_support/std",
diff --git a/substrate/core/test-runtime/src/genesismap.rs b/substrate/core/test-runtime/src/genesismap.rs
index da7d9cf4ef..8d5be8355e 100644
--- a/substrate/core/test-runtime/src/genesismap.rs
+++ b/substrate/core/test-runtime/src/genesismap.rs
@@ -19,7 +19,7 @@
 use std::collections::HashMap;
 use runtime_io::{blake2_256, twox_128};
 use super::{AuthorityId, AccountId, WASM_BINARY};
-use parity_codec::{Encode, KeyedVec, Joiner};
+use codec::{Encode, KeyedVec, Joiner};
 use primitives::{ChangesTrieConfiguration, map, storage::well_known_keys};
 use sr_primitives::traits::Block;
 
diff --git a/substrate/core/test-runtime/src/lib.rs b/substrate/core/test-runtime/src/lib.rs
index 98d2437059..6492d27bbe 100644
--- a/substrate/core/test-runtime/src/lib.rs
+++ b/substrate/core/test-runtime/src/lib.rs
@@ -23,7 +23,7 @@ pub mod genesismap;
 pub mod system;
 
 use rstd::{prelude::*, marker::PhantomData};
-use parity_codec::{Encode, Decode, Input};
+use codec::{Encode, Decode, Input, Error};
 
 use primitives::Blake2Hasher;
 use trie_db::{TrieMut, Trie};
@@ -214,6 +214,8 @@ impl<B: BlockT> Encode for DecodeFails<B> {
 	}
 }
 
+impl<B: BlockT> codec::EncodeLike for DecodeFails<B> {}
+
 impl<B: BlockT> DecodeFails<B> {
 	/// Create a new instance.
 	pub fn new() -> DecodeFails<B> {
@@ -224,9 +226,8 @@ impl<B: BlockT> DecodeFails<B> {
 }
 
 impl<B: BlockT> Decode for DecodeFails<B> {
-	fn decode<I: Input>(_: &mut I) -> Option<Self> {
-		// decoding always fails
-		None
+	fn decode<I: Input>(_: &mut I) -> Result<Self, Error> {
+		Err("DecodeFails always fails".into())
 	}
 }
 
diff --git a/substrate/core/test-runtime/src/system.rs b/substrate/core/test-runtime/src/system.rs
index 30cd105328..c108672c83 100644
--- a/substrate/core/test-runtime/src/system.rs
+++ b/substrate/core/test-runtime/src/system.rs
@@ -25,7 +25,7 @@ use sr_primitives::traits::{Hash as HashT, BlakeTwo256, Header as _};
 use sr_primitives::generic;
 use sr_primitives::{ApplyError, ApplyOutcome, ApplyResult};
 use sr_primitives::transaction_validity::{TransactionValidity, ValidTransaction};
-use parity_codec::{KeyedVec, Encode};
+use codec::{KeyedVec, Encode};
 use super::{
 	AccountId, BlockNumber, Extrinsic, Transfer, H256 as Hash, Block, Header, Digest, AuthorityId
 };
diff --git a/substrate/core/transaction-pool/Cargo.toml b/substrate/core/transaction-pool/Cargo.toml
index 6d2465922b..c18a50778d 100644
--- a/substrate/core/transaction-pool/Cargo.toml
+++ b/substrate/core/transaction-pool/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2018"
 derive_more = "0.14.0"
 futures = "0.1"
 log = "0.4"
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 parking_lot = "0.8.0"
 sr-primitives = { path = "../sr-primitives" }
 client = { package = "substrate-client", path = "../client" }
diff --git a/substrate/core/transaction-pool/graph/Cargo.toml b/substrate/core/transaction-pool/graph/Cargo.toml
index 2ecb6ab188..8010b07ac4 100644
--- a/substrate/core/transaction-pool/graph/Cargo.toml
+++ b/substrate/core/transaction-pool/graph/Cargo.toml
@@ -16,5 +16,5 @@ sr-primitives = { path = "../../sr-primitives" }
 [dev-dependencies]
 assert_matches = "1.3.0"
 env_logger = "0.6.1"
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 test_runtime = { package = "substrate-test-runtime", path = "../../test-runtime" }
diff --git a/substrate/core/transaction-pool/graph/src/pool.rs b/substrate/core/transaction-pool/graph/src/pool.rs
index 8f76a17ed9..6eec0d222f 100644
--- a/substrate/core/transaction-pool/graph/src/pool.rs
+++ b/substrate/core/transaction-pool/graph/src/pool.rs
@@ -454,7 +454,7 @@ mod tests {
 	use super::*;
 	use sr_primitives::transaction_validity::ValidTransaction;
 	use futures::Stream;
-	use parity_codec::Encode;
+	use codec::Encode;
 	use test_runtime::{Block, Extrinsic, Transfer, H256, AccountId};
 	use assert_matches::assert_matches;
 	use crate::watcher;
diff --git a/substrate/core/transaction-pool/src/api.rs b/substrate/core/transaction-pool/src/api.rs
index 668a9b8013..c0c4c787a5 100644
--- a/substrate/core/transaction-pool/src/api.rs
+++ b/substrate/core/transaction-pool/src/api.rs
@@ -21,7 +21,7 @@ use std::{
 	marker::PhantomData,
 };
 use client::{runtime_api::TaggedTransactionQueue, blockchain::HeaderBackend};
-use parity_codec::Encode;
+use codec::Encode;
 use txpool;
 use primitives::{
 	H256,
diff --git a/substrate/core/transaction-pool/src/tests.rs b/substrate/core/transaction-pool/src/tests.rs
index 7fb94936d2..71ed988e5e 100644
--- a/substrate/core/transaction-pool/src/tests.rs
+++ b/substrate/core/transaction-pool/src/tests.rs
@@ -17,7 +17,7 @@
 
 use super::*;
 
-use parity_codec::Encode;
+use codec::Encode;
 use txpool::{self, Pool};
 use test_client::{runtime::{AccountId, Block, Hash, Index, Extrinsic, Transfer}, AccountKeyring::{self, *}};
 use sr_primitives::{
diff --git a/substrate/core/trie/Cargo.toml b/substrate/core/trie/Cargo.toml
index 8659462bc4..82945d90f3 100644
--- a/substrate/core/trie/Cargo.toml
+++ b/substrate/core/trie/Cargo.toml
@@ -2,7 +2,7 @@
 name = "substrate-trie"
 version = "2.0.0"
 authors = ["Parity Technologies <admin@parity.io>"]
-description = "Patricia trie stuff using a parity-codec node format"
+description = "Patricia trie stuff using a parity-scale-codec node format"
 repository = "https://github.com/paritytech/parity-common"
 license = "GPL-3.0"
 edition = "2018"
@@ -12,7 +12,7 @@ name = "bench"
 harness = false
 
 [dependencies]
-codec = { package = "parity-codec", version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 rstd = { package = "sr-std", path = "../sr-std", default-features = false }
 hash-db = { version = "0.15.0", default-features = false }
 trie-db = { version = "0.15.0", default-features = false }
diff --git a/substrate/core/trie/src/error.rs b/substrate/core/trie/src/error.rs
index 1e386146d3..c18db37f35 100644
--- a/substrate/core/trie/src/error.rs
+++ b/substrate/core/trie/src/error.rs
@@ -12,22 +12,36 @@ use std::fmt;
 use std::error::Error as StdError;
 
 #[derive(Debug, PartialEq, Eq, Clone)]
-/// Error concerning the Parity-Codec based decoder.
+/// Error for trie node decoding.
 pub enum Error {
 	/// Bad format.
 	BadFormat,
+	/// Decoding error.
+	Decode(codec::Error)
+}
+
+impl From<codec::Error> for Error {
+	fn from(x: codec::Error) -> Self {
+		Error::Decode(x)
+	}
 }
 
 #[cfg(feature="std")]
 impl StdError for Error {
 	fn description(&self) -> &str {
-		"codec error"
+		match self {
+			Error::BadFormat => "Bad format error",
+			Error::Decode(_) => "Decoding error",
+		}
 	}
 }
 
 #[cfg(feature="std")]
 impl fmt::Display for Error {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		fmt::Debug::fmt(&self, f)
+		match self {
+			Error::Decode(e) => write!(f, "Decode error: {}", e.what()),
+			Error::BadFormat => write!(f, "Bad format"),
+		}
 	}
 }
diff --git a/substrate/core/trie/src/node_codec.rs b/substrate/core/trie/src/node_codec.rs
index 8c01beda6b..950f0c726f 100644
--- a/substrate/core/trie/src/node_codec.rs
+++ b/substrate/core/trie/src/node_codec.rs
@@ -49,7 +49,7 @@ impl<H: Hasher> NodeCodecT<H> for NodeCodec<H> {
 
 	fn decode(data: &[u8]) -> rstd::result::Result<Node, Self::Error> {
 		let input = &mut &*data;
-		let head = NodeHeader::decode(input).ok_or(Error::BadFormat)?;
+		let head = NodeHeader::decode(input)?;
 		match head {
 			NodeHeader::Null => Ok(Node::Empty),
 			NodeHeader::Branch(has_value, nibble_count) => {
@@ -69,7 +69,7 @@ impl<H: Hasher> NodeCodecT<H> for NodeCodec<H> {
 				let bitmap_slice = take(input, BITMAP_LENGTH).ok_or(Error::BadFormat)?;
 				let bitmap = Bitmap::decode(&bitmap_slice[..])?;
 				let value = if has_value {
-					let count = <Compact<u32>>::decode(input).ok_or(Error::BadFormat)?.0 as usize;
+					let count = <Compact<u32>>::decode(input)?.0 as usize;
 					Some(take(input, count).ok_or(Error::BadFormat)?)
 				} else {
 					None
@@ -78,7 +78,7 @@ impl<H: Hasher> NodeCodecT<H> for NodeCodec<H> {
 
 				for i in 0..nibble_ops::NIBBLE_LENGTH {
 					if bitmap.value_at(i) {
-						let count = <Compact<u32>>::decode(input).ok_or(Error::BadFormat)?.0 as usize;
+						let count = <Compact<u32>>::decode(input)?.0 as usize;
 						children[i] = Some(take(input, count).ok_or(Error::BadFormat)?);
 					}
 				}
@@ -98,7 +98,7 @@ impl<H: Hasher> NodeCodecT<H> for NodeCodec<H> {
 					nibble_data,
 					nibble_ops::number_padding(nibble_count),
 				);
-				let count = <Compact<u32>>::decode(input).ok_or(Error::BadFormat)?.0 as usize;
+				let count = <Compact<u32>>::decode(input)?.0 as usize;
 				Ok(Node::Leaf(nibble_slice, take(input, count).ok_or(Error::BadFormat)?))
 			}
 		}
@@ -229,11 +229,8 @@ const BITMAP_LENGTH: usize = 2;
 pub(crate) struct Bitmap(u16);
 
 impl Bitmap {
-
 	pub fn decode(data: &[u8]) -> Result<Self, Error> {
-		u16::decode(&mut &data[..])
-			.ok_or(Error::BadFormat)
-			.map(|v|Bitmap(v))
+		Ok(Bitmap(u16::decode(&mut &data[..])?))
 	}
 
 	pub fn value_at(&self, i: usize) -> bool {
diff --git a/substrate/core/trie/src/node_header.rs b/substrate/core/trie/src/node_header.rs
index e4c38bd075..50d3d87250 100644
--- a/substrate/core/trie/src/node_header.rs
+++ b/substrate/core/trie/src/node_header.rs
@@ -50,18 +50,20 @@ impl Encode for NodeHeader {
 	}
 }
 
+impl codec::EncodeLike for NodeHeader {}
+
 impl Decode for NodeHeader {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+	fn decode<I: Input>(input: &mut I) -> Result<Self, codec::Error> {
 		let i = input.read_byte()?;
 		if i == trie_constants::EMPTY_TRIE {
-			return Some(NodeHeader::Null);
+			return Ok(NodeHeader::Null);
 		}
 		match i & (0b11 << 6) {
-			trie_constants::LEAF_PREFIX_MASK => Some(NodeHeader::Leaf(decode_size(i, input)?)),
-			trie_constants::BRANCH_WITHOUT_MASK => Some(NodeHeader::Branch(false, decode_size(i, input)?)),
-			trie_constants::BRANCH_WITH_MASK => Some(NodeHeader::Branch(true, decode_size(i, input)?)),
+			trie_constants::LEAF_PREFIX_MASK => Ok(NodeHeader::Leaf(decode_size(i, input)?)),
+			trie_constants::BRANCH_WITHOUT_MASK => Ok(NodeHeader::Branch(false, decode_size(i, input)?)),
+			trie_constants::BRANCH_WITH_MASK => Ok(NodeHeader::Branch(true, decode_size(i, input)?)),
 			// do not allow any special encoding
-			_ => None,
+			_ => Err("Unallowed encoding".into()),
 		}
 	}
 }
@@ -103,18 +105,18 @@ fn encode_size_and_prefix(size: usize, prefix: u8, out: &mut impl Output) {
 }
 
 /// Decode size only from stream input and header byte.
-fn decode_size(first: u8, input: &mut impl Input) -> Option<usize> {
+fn decode_size(first: u8, input: &mut impl Input) -> Result<usize, codec::Error> {
 	let mut result = (first & 255u8 >> 2) as usize;
 	if result < 63 {
-		return Some(result);
+		return Ok(result);
 	}
 	result -= 1;
 	while result <= trie_constants::NIBBLE_SIZE_BOUND {
 		let n = input.read_byte()? as usize;
 		if n < 255 {
-			return Some(result + n + 1);
+			return Ok(result + n + 1);
 		}
 		result += 255;
 	}
-	Some(trie_constants::NIBBLE_SIZE_BOUND)
+	Ok(trie_constants::NIBBLE_SIZE_BOUND)
 }
diff --git a/substrate/core/utils/fork-tree/Cargo.toml b/substrate/core/utils/fork-tree/Cargo.toml
index c41914e07a..fa37161dc2 100644
--- a/substrate/core/utils/fork-tree/Cargo.toml
+++ b/substrate/core/utils/fork-tree/Cargo.toml
@@ -5,4 +5,4 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-parity-codec = { version = "4.1.1", features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", features = ["derive"] }
diff --git a/substrate/core/utils/fork-tree/src/lib.rs b/substrate/core/utils/fork-tree/src/lib.rs
index c6debe859a..5a7480e065 100644
--- a/substrate/core/utils/fork-tree/src/lib.rs
+++ b/substrate/core/utils/fork-tree/src/lib.rs
@@ -20,7 +20,7 @@
 #![warn(missing_docs)]
 
 use std::fmt;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 
 /// Error occured when iterating with the tree.
 #[derive(Clone, Debug, PartialEq)]
diff --git a/substrate/node-template/Cargo.toml b/substrate/node-template/Cargo.toml
index ad626beb0b..ea48ff7f68 100644
--- a/substrate/node-template/Cargo.toml
+++ b/substrate/node-template/Cargo.toml
@@ -17,7 +17,7 @@ log = "0.4"
 tokio = "0.1"
 exit-future = "0.1"
 parking_lot = "0.8.0"
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 trie-root = "0.15.0"
 sr-io = { path = "../core/sr-io" }
 substrate-cli = { path = "../core/cli" }
diff --git a/substrate/node-template/runtime/Cargo.toml b/substrate/node-template/runtime/Cargo.toml
index 1bde247930..878374cf6a 100644
--- a/substrate/node-template/runtime/Cargo.toml
+++ b/substrate/node-template/runtime/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true, features = ["derive"] }
 safe-mix = { version = "1.0", default-features = false }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default_features = false }
 runtime-io = { package = "sr-io", path = "../../core/sr-io", default_features = false }
 version = { package = "sr-version", path = "../../core/sr-version", default_features = false }
@@ -31,7 +31,7 @@ wasm-builder-runner = { package = "substrate-wasm-builder-runner", version = "1.
 [features]
 default = ["std"]
 std = [
-	"parity-codec/std",
+	"codec/std",
 	"client/std",
 	"rstd/std",
 	"runtime-io/std",
diff --git a/substrate/node/cli/Cargo.toml b/substrate/node/cli/Cargo.toml
index d3d48ebe01..f95f688ac3 100644
--- a/substrate/node/cli/Cargo.toml
+++ b/substrate/node/cli/Cargo.toml
@@ -12,7 +12,7 @@ tokio = "0.1.7"
 futures = "0.1"
 exit-future = "0.1"
 cli = { package = "substrate-cli", path = "../../core/cli" }
-parity-codec = { version = "4.1.1" }
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 sr-io = { path = "../../core/sr-io" }
 client = { package = "substrate-client", path = "../../core/client" }
 primitives = { package = "substrate-primitives", path = "../../core/primitives" }
diff --git a/substrate/node/cli/src/factory_impl.rs b/substrate/node/cli/src/factory_impl.rs
index dffd084c5f..41ac992abb 100644
--- a/substrate/node/cli/src/factory_impl.rs
+++ b/substrate/node/cli/src/factory_impl.rs
@@ -21,11 +21,10 @@
 use rand::{Rng, SeedableRng};
 use rand::rngs::StdRng;
 
-use parity_codec::Decode;
+use codec::{Encode, Decode};
 use keyring::sr25519::Keyring;
 use node_runtime::{Call, CheckedExtrinsic, UncheckedExtrinsic, SignedExtra, BalancesCall, ExistentialDeposit};
 use primitives::{sr25519, crypto::Pair};
-use parity_codec::Encode;
 use sr_primitives::{generic::Era, traits::{Block as BlockT, Header as HeaderT, SignedExtension}};
 use substrate_service::ServiceFactory;
 use transaction_factory::RuntimeAdapter;
diff --git a/substrate/node/cli/src/service.rs b/substrate/node/cli/src/service.rs
index 8fbd425da3..0b887bb55a 100644
--- a/substrate/node/cli/src/service.rs
+++ b/substrate/node/cli/src/service.rs
@@ -265,7 +265,7 @@ mod tests {
 	use node_primitives::DigestItem;
 	use node_runtime::{BalancesCall, Call, UncheckedExtrinsic};
 	use node_runtime::constants::{currency::CENTS, time::SLOT_DURATION};
-	use parity_codec::{Encode, Decode};
+	use codec::{Encode, Decode};
 	use primitives::{
 		crypto::Pair as CryptoPair, blake2_256,
 		sr25519::Public as AddressPublic, H256,
diff --git a/substrate/node/executor/Cargo.toml b/substrate/node/executor/Cargo.toml
index 44a56ee4a6..d1886c2ab6 100644
--- a/substrate/node/executor/Cargo.toml
+++ b/substrate/node/executor/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 
 [dependencies]
 trie-root = "0.15.0"
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 runtime_io = { package = "sr-io", path = "../../core/sr-io" }
 state_machine = { package = "substrate-state-machine", path = "../../core/state-machine" }
 substrate-executor = { path = "../../core/executor" }
diff --git a/substrate/node/executor/src/lib.rs b/substrate/node/executor/src/lib.rs
index 572d0ca149..711fdcdb69 100644
--- a/substrate/node/executor/src/lib.rs
+++ b/substrate/node/executor/src/lib.rs
@@ -40,7 +40,7 @@ mod tests {
 	use {balances, contracts, indices, staking, system, timestamp};
 	use runtime_io;
 	use substrate_executor::WasmExecutor;
-	use parity_codec::{Encode, Decode, Joiner};
+	use codec::{Encode, Decode, Joiner};
 	use keyring::{AccountKeyring, Ed25519Keyring, Sr25519Keyring};
 	use runtime_support::{Hashable, StorageValue, StorageMap, assert_eq_error_rate, traits::Currency};
 	use state_machine::{CodeExecutor, Externalities, TestExternalities as CoreTestExternalities};
diff --git a/substrate/node/primitives/Cargo.toml b/substrate/node/primitives/Cargo.toml
index 36ea1eb414..05fb231205 100644
--- a/substrate/node/primitives/Cargo.toml
+++ b/substrate/node/primitives/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true, features = ["derive"] }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives", path = "../../core/primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
@@ -18,7 +18,7 @@ pretty_assertions = "0.5"
 [features]
 default = ["std"]
 std = [
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"rstd/std",
 	"sr-primitives/std",
diff --git a/substrate/node/runtime/Cargo.toml b/substrate/node/runtime/Cargo.toml
index c40e6d7796..da6180889e 100644
--- a/substrate/node/runtime/Cargo.toml
+++ b/substrate/node/runtime/Cargo.toml
@@ -8,7 +8,7 @@ build = "build.rs"
 [dependencies]
 integer-sqrt = { version = "0.1.2" }
 safe-mix = { version = "1.0", default-features = false }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
 client = { package = "substrate-client", path = "../../core/client", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
@@ -50,7 +50,7 @@ no_std = [
 	"contracts/core",
 ]
 std = [
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"rstd/std",
 	"sr-primitives/std",
diff --git a/substrate/node/runtime/src/lib.rs b/substrate/node/runtime/src/lib.rs
index 06285571ba..f89e1f4a86 100644
--- a/substrate/node/runtime/src/lib.rs
+++ b/substrate/node/runtime/src/lib.rs
@@ -80,7 +80,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
 	spec_version: 129,
-	impl_version: 129,
+	impl_version: 130,
 	apis: RUNTIME_API_VERSIONS,
 };
 
diff --git a/substrate/srml/assets/Cargo.toml b/substrate/srml/assets/Cargo.toml
index d1526c8be8..2badb46130 100644
--- a/substrate/srml/assets/Cargo.toml
+++ b/substrate/srml/assets/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true }
-parity-codec = { version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 # Needed for various traits. In our case, `OnFinalize`.
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 # Needed for type-safe access to storage DB.
@@ -23,7 +23,7 @@ runtime_io = { package = "sr-io", path = "../../core/sr-io" }
 default = ["std"]
 std = [
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"sr-primitives/std",
 	"srml-support/std",
 	"system/std",
diff --git a/substrate/srml/aura/Cargo.toml b/substrate/srml/aura/Cargo.toml
index 9ce3658283..6ce9c87c5c 100644
--- a/substrate/srml/aura/Cargo.toml
+++ b/substrate/srml/aura/Cargo.toml
@@ -5,7 +5,7 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 serde = { version = "1.0", optional = true }
 inherents = { package = "substrate-inherents", path = "../../core/inherents", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
@@ -27,7 +27,7 @@ runtime_io = { package = "sr-io", path = "../../core/sr-io" }
 default = ["std"]
 std = [
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"srml-support/std",
 	"sr-primitives/std",
diff --git a/substrate/srml/aura/src/lib.rs b/substrate/srml/aura/src/lib.rs
index 1402cb1d9e..a79b5c46a5 100644
--- a/substrate/srml/aura/src/lib.rs
+++ b/substrate/srml/aura/src/lib.rs
@@ -51,7 +51,7 @@
 pub use timestamp;
 
 use rstd::{result, prelude::*};
-use parity_codec::Encode;
+use codec::Encode;
 use srml_support::{decl_storage, decl_module, Parameter, storage::StorageValue, traits::Get};
 use sr_primitives::{
 	traits::{SaturatedConversion, Saturating, Zero, One, Member, IsMember, TypedKey},
@@ -65,7 +65,7 @@ use inherents::{RuntimeString, InherentIdentifier, InherentData, ProvideInherent
 use inherents::{InherentDataProviders, ProvideInherentData};
 use substrate_consensus_aura_primitives::{AURA_ENGINE_ID, ConsensusLog};
 #[cfg(feature = "std")]
-use parity_codec::Decode;
+use codec::Decode;
 
 mod mock;
 mod tests;
@@ -138,7 +138,7 @@ impl ProvideInherentData for InherentDataProvider {
 	}
 
 	fn error_to_string(&self, error: &[u8]) -> Option<String> {
-		RuntimeString::decode(&mut &error[..]).map(Into::into)
+		RuntimeString::decode(&mut &error[..]).map(Into::into).ok()
 	}
 }
 
diff --git a/substrate/srml/authorship/Cargo.toml b/substrate/srml/authorship/Cargo.toml
index 29de88ba2c..f470675b4b 100644
--- a/substrate/srml/authorship/Cargo.toml
+++ b/substrate/srml/authorship/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 
 [dependencies]
 primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 srml-support = { path = "../support", default-features = false }
@@ -17,7 +17,7 @@ runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features =
 [features]
 default = ["std"]
 std = [
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"sr-primitives/std",
 	"rstd/std",
diff --git a/substrate/srml/authorship/src/lib.rs b/substrate/srml/authorship/src/lib.rs
index 2325dac5f3..e46e2f232d 100644
--- a/substrate/srml/authorship/src/lib.rs
+++ b/substrate/srml/authorship/src/lib.rs
@@ -25,7 +25,7 @@ use rstd::collections::btree_set::BTreeSet;
 use srml_support::{decl_module, decl_storage, for_each_tuple, StorageValue};
 use srml_support::traits::{FindAuthor, VerifySeal, Get};
 use srml_support::dispatch::Result as DispatchResult;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use system::ensure_none;
 use sr_primitives::traits::{SimpleArithmetic, Header as HeaderT, One, Zero};
 use sr_primitives::weights::SimpleDispatchInfo;
@@ -382,7 +382,7 @@ mod tests {
 		{
 			for (id, data) in digests {
 				if id == TEST_ID {
-					return u64::decode(&mut &data[..]);
+					return u64::decode(&mut &data[..]).ok();
 				}
 			}
 
@@ -409,8 +409,8 @@ mod tests {
 			for (id, seal) in seals {
 				if id == TEST_ID {
 					match u64::decode(&mut &seal[..]) {
-						None => return Err("wrong seal"),
-						Some(a) => {
+						Err(_) => return Err("wrong seal"),
+						Ok(a) => {
 							if a != author {
 								return Err("wrong author in seal");
 							}
diff --git a/substrate/srml/babe/Cargo.toml b/substrate/srml/babe/Cargo.toml
index ba47d8e278..2e2d3c84b0 100644
--- a/substrate/srml/babe/Cargo.toml
+++ b/substrate/srml/babe/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 hex-literal = "0.2"
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 serde = { version = "1.0.93", optional = true }
 inherents = { package = "substrate-inherents", path = "../../core/inherents", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
@@ -28,7 +28,7 @@ primitives = { package = "substrate-primitives",  path = "../../core/primitives"
 default = ["std"]
 std = [
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"srml-support/std",
 	"sr-primitives/std",
diff --git a/substrate/srml/babe/src/lib.rs b/substrate/srml/babe/src/lib.rs
index 8e72fdffd4..02099aace8 100644
--- a/substrate/srml/babe/src/lib.rs
+++ b/substrate/srml/babe/src/lib.rs
@@ -28,7 +28,7 @@ use sr_primitives::{generic::DigestItem, ConsensusEngineId};
 use sr_primitives::traits::{IsMember, SaturatedConversion, Saturating, RandomnessBeacon, Convert};
 #[cfg(feature = "std")]
 use timestamp::TimestampInherentData;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use inherents::{RuntimeString, InherentIdentifier, InherentData, ProvideInherent, MakeFatalError};
 #[cfg(feature = "std")]
 use inherents::{InherentDataProviders, ProvideInherentData};
@@ -103,7 +103,7 @@ impl ProvideInherentData for InherentDataProvider {
 	}
 
 	fn error_to_string(&self, error: &[u8]) -> Option<String> {
-		RuntimeString::decode(&mut &error[..]).map(Into::into)
+		RuntimeString::decode(&mut &error[..]).map(Into::into).ok()
 	}
 }
 
@@ -186,7 +186,7 @@ decl_module! {
 				.iter()
 				.filter_map(|s| s.as_pre_runtime())
 				.filter_map(|(id, mut data)| if id == BABE_ENGINE_ID {
-					RawBabePreDigest::decode(&mut data)
+					RawBabePreDigest::decode(&mut data).ok()
 				} else {
 					None
 				})
@@ -219,7 +219,7 @@ impl<T: Trait> FindAuthor<u32> for Module<T> {
 	{
 		for (id, mut data) in digests.into_iter() {
 			if id == BABE_ENGINE_ID {
-				return Some(RawBabePreDigest::decode(&mut data)?.authority_index);
+				return Some(RawBabePreDigest::decode(&mut data).ok()?.authority_index);
 			}
 		}
 		return None;
diff --git a/substrate/srml/balances/Cargo.toml b/substrate/srml/balances/Cargo.toml
index f096d506a4..d3ac0c96b3 100644
--- a/substrate/srml/balances/Cargo.toml
+++ b/substrate/srml/balances/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true }
 safe-mix = { version = "1.0", default-features = false}
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 substrate-keyring = { path = "../../core/keyring", optional = true }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
@@ -24,7 +24,7 @@ std = [
 	"serde",
 	"safe-mix/std",
 	"substrate-keyring",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"srml-support/std",
 	"sr-primitives/std",
diff --git a/substrate/srml/balances/src/lib.rs b/substrate/srml/balances/src/lib.rs
index bff5e90c32..b1aefccc67 100644
--- a/substrate/srml/balances/src/lib.rs
+++ b/substrate/srml/balances/src/lib.rs
@@ -151,7 +151,7 @@
 
 use rstd::prelude::*;
 use rstd::{cmp, result, mem};
-use parity_codec::{Codec, Encode, Decode};
+use codec::{Codec, Encode, Decode};
 use srml_support::{StorageValue, StorageMap, Parameter, decl_event, decl_storage, decl_module};
 use srml_support::traits::{
 	UpdateBalanceOutcome, Currency, OnFreeBalanceZero, OnUnbalanced,
diff --git a/substrate/srml/collective/Cargo.toml b/substrate/srml/collective/Cargo.toml
index 83d25593e4..7aaba7c29f 100644
--- a/substrate/srml/collective/Cargo.toml
+++ b/substrate/srml/collective/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true }
 safe-mix = { version = "1.0", default-features = false}
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
@@ -23,7 +23,7 @@ balances = { package = "srml-balances", path = "../balances" }
 default = ["std"]
 std = [
 	"safe-mix/std",
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"rstd/std",
 	"serde",
diff --git a/substrate/srml/contracts/Cargo.toml b/substrate/srml/contracts/Cargo.toml
index 33c32c8ea2..a013571edf 100644
--- a/substrate/srml/contracts/Cargo.toml
+++ b/substrate/srml/contracts/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true, features = ["derive"] }
 pwasm-utils = { version = "0.6.1", default-features = false }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 parity-wasm = { version = "0.31", default-features = false }
 wasmi-validation = { version = "0.1", default-features = false }
 primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
@@ -33,7 +33,7 @@ core = [
 ]
 std = [
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"sr-primitives/std",
 	"runtime-io/std",
diff --git a/substrate/srml/contracts/src/lib.rs b/substrate/srml/contracts/src/lib.rs
index 15d7b37a45..d28ee362eb 100644
--- a/substrate/srml/contracts/src/lib.rs
+++ b/substrate/srml/contracts/src/lib.rs
@@ -98,7 +98,7 @@ use crate::wasm::{WasmLoader, WasmVm};
 use serde::{Serialize, Deserialize};
 use primitives::crypto::UncheckedFrom;
 use rstd::{prelude::*, marker::PhantomData};
-use parity_codec::{Codec, Encode, Decode};
+use codec::{Codec, Encode, Decode};
 use runtime_io::blake2_256;
 use sr_primitives::traits::{
 	Hash, StaticLookup, Zero, MaybeSerializeDebug, Member
diff --git a/substrate/srml/contracts/src/tests.rs b/substrate/srml/contracts/src/tests.rs
index 5a53d8426f..80bb7af518 100644
--- a/substrate/srml/contracts/src/tests.rs
+++ b/substrate/srml/contracts/src/tests.rs
@@ -26,7 +26,7 @@ use crate::{
 };
 use assert_matches::assert_matches;
 use hex_literal::*;
-use parity_codec::{Decode, Encode, KeyedVec};
+use codec::{Decode, Encode, KeyedVec};
 use runtime_io;
 use runtime_io::with_externalities;
 use sr_primitives::testing::{Digest, DigestItem, Header, UintAuthorityId, H256};
diff --git a/substrate/srml/contracts/src/wasm/mod.rs b/substrate/srml/contracts/src/wasm/mod.rs
index 2c29b1ead1..f1db63870b 100644
--- a/substrate/srml/contracts/src/wasm/mod.rs
+++ b/substrate/srml/contracts/src/wasm/mod.rs
@@ -23,7 +23,7 @@ use crate::exec::{Ext, EmptyOutputBuf, VmExecResult};
 use crate::gas::GasMeter;
 
 use rstd::prelude::*;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use sandbox;
 
 #[macro_use]
diff --git a/substrate/srml/contracts/src/wasm/runtime.rs b/substrate/srml/contracts/src/wasm/runtime.rs
index 006ec5aad2..2c631d71d5 100644
--- a/substrate/srml/contracts/src/wasm/runtime.rs
+++ b/substrate/srml/contracts/src/wasm/runtime.rs
@@ -26,7 +26,7 @@ use sandbox;
 use system;
 use rstd::prelude::*;
 use rstd::mem;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use sr_primitives::traits::{Bounded, SaturatedConversion};
 
 /// Enumerates all possible *special* trap conditions.
@@ -325,12 +325,12 @@ define_env!(Env, <E: Ext>,
 		let callee = {
 			let callee_buf = read_sandbox_memory(ctx, callee_ptr, callee_len)?;
 			<<E as Ext>::T as system::Trait>::AccountId::decode(&mut &callee_buf[..])
-				.ok_or_else(|| sandbox::HostError)?
+				.map_err(|_| sandbox::HostError)?
 		};
 		let value = {
 			let value_buf = read_sandbox_memory(ctx, value_ptr, value_len)?;
 			BalanceOf::<<E as Ext>::T>::decode(&mut &value_buf[..])
-				.ok_or_else(|| sandbox::HostError)?
+				.map_err(|_| sandbox::HostError)?
 		};
 		let input_data = read_sandbox_memory(ctx, input_data_ptr, input_data_len)?;
 
@@ -399,12 +399,12 @@ define_env!(Env, <E: Ext>,
 	) -> u32 => {
 		let code_hash = {
 			let code_hash_buf = read_sandbox_memory(ctx, code_hash_ptr, code_hash_len)?;
-			<CodeHash<<E as Ext>::T>>::decode(&mut &code_hash_buf[..]).ok_or_else(|| sandbox::HostError)?
+			<CodeHash<<E as Ext>::T>>::decode(&mut &code_hash_buf[..]).map_err(|_| sandbox::HostError)?
 		};
 		let value = {
 			let value_buf = read_sandbox_memory(ctx, value_ptr, value_len)?;
 			BalanceOf::<<E as Ext>::T>::decode(&mut &value_buf[..])
-				.ok_or_else(|| sandbox::HostError)?
+				.map_err(|_| sandbox::HostError)?
 		};
 		let input_data = read_sandbox_memory(ctx, input_data_ptr, input_data_len)?;
 
@@ -569,7 +569,7 @@ define_env!(Env, <E: Ext>,
 		let call = {
 			let call_buf = read_sandbox_memory(ctx, call_ptr, call_len)?;
 			<<<E as Ext>::T as Trait>::Call>::decode(&mut &call_buf[..])
-				.ok_or_else(|| sandbox::HostError)?
+				.map_err(|_| sandbox::HostError)?
 		};
 
 		// Charge gas for dispatching this call.
@@ -618,12 +618,12 @@ define_env!(Env, <E: Ext>,
 		let dest = {
 			let dest_buf = read_sandbox_memory(ctx, dest_ptr, dest_len)?;
 			<<E as Ext>::T as system::Trait>::AccountId::decode(&mut &dest_buf[..])
-				.ok_or_else(|| sandbox::HostError)?
+				.map_err(|_| sandbox::HostError)?
 		};
 		let code_hash = {
 			let code_hash_buf = read_sandbox_memory(ctx, code_hash_ptr, code_hash_len)?;
 			<CodeHash<<E as Ext>::T>>::decode(&mut &code_hash_buf[..])
-				.ok_or_else(|| sandbox::HostError)?
+				.map_err(|_| sandbox::HostError)?
 		};
 		let rent_allowance = {
 			let rent_allowance_buf = read_sandbox_memory(
@@ -632,7 +632,7 @@ define_env!(Env, <E: Ext>,
 				rent_allowance_len
 			)?;
 			BalanceOf::<<E as Ext>::T>::decode(&mut &rent_allowance_buf[..])
-				.ok_or_else(|| sandbox::HostError)?
+				.map_err(|_| sandbox::HostError)?
 		};
 		let delta = {
 			// We don't use `with_capacity` here to not eagerly allocate the user specified amount
@@ -717,7 +717,7 @@ define_env!(Env, <E: Ext>,
 			_ => {
 				let topics_buf = read_sandbox_memory(ctx, topics_ptr, topics_len)?;
 				Vec::<TopicOf<<E as Ext>::T>>::decode(&mut &topics_buf[..])
-					.ok_or_else(|| sandbox::HostError)?
+					.map_err(|_| sandbox::HostError)?
 			}
 		};
 
@@ -757,7 +757,7 @@ define_env!(Env, <E: Ext>,
 		let value = {
 			let value_buf = read_sandbox_memory(ctx, value_ptr, value_len)?;
 			BalanceOf::<<E as Ext>::T>::decode(&mut &value_buf[..])
-				.ok_or_else(|| sandbox::HostError)?
+				.map_err(|_| sandbox::HostError)?
 		};
 		ctx.ext.set_rent_allowance(value);
 
diff --git a/substrate/srml/democracy/Cargo.toml b/substrate/srml/democracy/Cargo.toml
index baf1488d42..b6341a8225 100644
--- a/substrate/srml/democracy/Cargo.toml
+++ b/substrate/srml/democracy/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true, features = ["derive"] }
 safe-mix = { version = "1.0", default-features = false}
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
@@ -23,7 +23,7 @@ default = ["std"]
 std = [
 	"serde",
 	"safe-mix/std",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"runtime_io/std",
 	"srml-support/std",
diff --git a/substrate/srml/democracy/src/lib.rs b/substrate/srml/democracy/src/lib.rs
index ae53a53bb8..332ad91358 100644
--- a/substrate/srml/democracy/src/lib.rs
+++ b/substrate/srml/democracy/src/lib.rs
@@ -22,7 +22,7 @@ use rstd::prelude::*;
 use rstd::{result, convert::TryFrom};
 use sr_primitives::traits::{Zero, Bounded, CheckedMul, CheckedDiv, EnsureOrigin, Hash};
 use sr_primitives::weights::SimpleDispatchInfo;
-use parity_codec::{Encode, Decode, Input, Output};
+use codec::{Encode, Decode, Input, Output, Error};
 use srml_support::{
 	decl_module, decl_storage, decl_event, ensure,
 	StorageValue, StorageMap, Parameter, Dispatchable, IsSubType, EnumerableStorageMap,
@@ -154,12 +154,15 @@ impl Encode for Vote {
 	}
 }
 
+impl codec::EncodeLike for Vote {}
+
 impl Decode for Vote {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+	fn decode<I: Input>(input: &mut I) -> core::result::Result<Self, Error> {
 		let b = input.read_byte()?;
-		Some(Vote {
+		Ok(Vote {
 			aye: (b & 0b1000_0000) == 0b1000_0000,
-			conviction: Conviction::try_from(b & 0b0111_1111).ok()?,
+			conviction: Conviction::try_from(b & 0b0111_1111)
+				.map_err(|_| Error::from("Invalid conviction"))?,
 		})
 	}
 }
diff --git a/substrate/srml/democracy/src/vote_threshold.rs b/substrate/srml/democracy/src/vote_threshold.rs
index 96e5849e43..d304c36f32 100644
--- a/substrate/srml/democracy/src/vote_threshold.rs
+++ b/substrate/srml/democracy/src/vote_threshold.rs
@@ -18,7 +18,7 @@
 
 #[cfg(feature = "std")]
 use serde::{Serialize, Deserialize};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use sr_primitives::traits::{Zero, IntegerSquareRoot};
 use rstd::ops::{Add, Mul, Div, Rem};
 
diff --git a/substrate/srml/elections/Cargo.toml b/substrate/srml/elections/Cargo.toml
index dc004471d5..d6043bb2d0 100644
--- a/substrate/srml/elections/Cargo.toml
+++ b/substrate/srml/elections/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true }
 safe-mix = { version = "1.0", default-features = false}
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
@@ -23,7 +23,7 @@ balances = { package = "srml-balances", path = "../balances" }
 default = ["std"]
 std = [
 	"safe-mix/std",
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"rstd/std",
 	"serde",
diff --git a/substrate/srml/elections/src/lib.rs b/substrate/srml/elections/src/lib.rs
index 0e761c94c8..e8fbb75dc3 100644
--- a/substrate/srml/elections/src/lib.rs
+++ b/substrate/srml/elections/src/lib.rs
@@ -35,7 +35,7 @@ use srml_support::{
 		OnUnbalanced, ReservableCurrency, WithdrawReason, WithdrawReasons, ChangeMembers
 	}
 };
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use system::{self, ensure_signed, ensure_root};
 
 // no polynomial attacks:
diff --git a/substrate/srml/example/Cargo.toml b/substrate/srml/example/Cargo.toml
index 2cbd707f18..87069a487a 100644
--- a/substrate/srml/example/Cargo.toml
+++ b/substrate/srml/example/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true }
-parity-codec = { version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 srml-support = { path = "../support", default-features = false }
 system = { package = "srml-system", path = "../system", default-features = false }
 balances = { package = "srml-balances", path = "../balances", default-features = false }
@@ -20,7 +20,7 @@ primitives = { package = "substrate-primitives",  path = "../../core/primitives"
 default = ["std"]
 std = [
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"sr-primitives/std",
 	"srml-support/std",
 	"system/std",
diff --git a/substrate/srml/executive/Cargo.toml b/substrate/srml/executive/Cargo.toml
index e732c9b636..e398a95189 100644
--- a/substrate/srml/executive/Cargo.toml
+++ b/substrate/srml/executive/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
@@ -25,7 +25,7 @@ std = [
 	"rstd/std",
 	"srml-support/std",
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"sr-primitives/std",
 	"runtime_io/std",
 	"system/std",
diff --git a/substrate/srml/executive/src/lib.rs b/substrate/srml/executive/src/lib.rs
index 062badd932..54ea3a3f14 100644
--- a/substrate/srml/executive/src/lib.rs
+++ b/substrate/srml/executive/src/lib.rs
@@ -82,7 +82,7 @@ use sr_primitives::{generic::Digest, traits::{
 	OnInitialize, NumberFor, Block as BlockT, OffchainWorker, ValidateUnsigned
 }};
 use srml_support::Dispatchable;
-use parity_codec::{Codec, Encode};
+use codec::{Codec, Encode};
 use system::{extrinsics_root, DigestOf};
 use sr_primitives::{ApplyOutcome, ApplyError};
 use sr_primitives::transaction_validity::TransactionValidity;
diff --git a/substrate/srml/finality-tracker/Cargo.toml b/substrate/srml/finality-tracker/Cargo.toml
index 3dfd453c75..65ac540b6b 100644
--- a/substrate/srml/finality-tracker/Cargo.toml
+++ b/substrate/srml/finality-tracker/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", default-features = false, features = ["derive"] }
-parity-codec = { version = "4.1.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
 inherents = { package = "substrate-inherents", path = "../../core/inherents", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
@@ -21,7 +21,7 @@ sr-io = { path = "../../core/sr-io", default-features = false }
 default = ["std"]
 std = [
 	"serde/std",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"srml-support/std",
 	"sr-primitives/std",
diff --git a/substrate/srml/finality-tracker/src/lib.rs b/substrate/srml/finality-tracker/src/lib.rs
index f0e2ae0f54..4c3d975d7e 100644
--- a/substrate/srml/finality-tracker/src/lib.rs
+++ b/substrate/srml/finality-tracker/src/lib.rs
@@ -25,13 +25,13 @@ use inherents::{
 use srml_support::StorageValue;
 use sr_primitives::traits::{One, Zero, SaturatedConversion};
 use rstd::{prelude::*, result, cmp, vec};
-use parity_codec::Decode;
+use codec::Decode;
 use srml_support::{decl_module, decl_storage, for_each_tuple};
 use srml_support::traits::Get;
 use srml_system::{ensure_none, Trait as SystemTrait};
 
 #[cfg(feature = "std")]
-use parity_codec::Encode;
+use codec::Encode;
 
 /// The identifier for the `finalnum` inherent.
 pub const INHERENT_IDENTIFIER: InherentIdentifier = *b"finalnum";
diff --git a/substrate/srml/generic-asset/Cargo.toml b/substrate/srml/generic-asset/Cargo.toml
index 0e10e15590..65e21c3b11 100644
--- a/substrate/srml/generic-asset/Cargo.toml
+++ b/substrate/srml/generic-asset/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 support = { package = "srml-support", path = "../support", default-features = false }
@@ -20,7 +20,7 @@ primitives = { package = "substrate-primitives",  path = "../../core/primitives"
 default = ["std"]
 std =[
     "serde/std",
-    "parity-codec/std",
+    "codec/std",
     "rstd/std",
     "sr-primitives/std",
     "support/std",
diff --git a/substrate/srml/generic-asset/src/lib.rs b/substrate/srml/generic-asset/src/lib.rs
index 60d1f0a3ff..57369b100e 100644
--- a/substrate/srml/generic-asset/src/lib.rs
+++ b/substrate/srml/generic-asset/src/lib.rs
@@ -151,7 +151,7 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use parity_codec::{Decode, Encode, HasCompact, Input, Output};
+use codec::{Decode, Encode, HasCompact, Input, Output, Error};
 
 use sr_primitives::traits::{
 	CheckedAdd, CheckedSub, MaybeSerializeDebug, Member, One, Saturating, SimpleArithmetic, Zero, Bounded
@@ -284,10 +284,12 @@ impl<AccountId: Encode> Encode for PermissionVersions<AccountId> {
 	}
 }
 
+impl<AccountId: Encode> codec::EncodeLike for PermissionVersions<AccountId> {}
+
 impl<AccountId: Decode> Decode for PermissionVersions<AccountId> {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+	fn decode<I: Input>(input: &mut I) -> core::result::Result<Self, Error> {
 		let version = PermissionVersionNumber::decode(input)?;
-		Some(
+		Ok(
 			match version {
 				PermissionVersionNumber::V1 => PermissionVersions::V1(Decode::decode(input)?)
 			}
@@ -484,7 +486,7 @@ decl_storage! {
 				config.endowed_accounts.iter().for_each(|account_id| {
 					storage.insert(
 						<FreeBalance<T>>::key_for(asset_id, account_id),
-						<T::Balance as parity_codec::Encode>::encode(&config.initial_balance)
+						<T::Balance as codec::Encode>::encode(&config.initial_balance)
 					);
 				});
 			});
diff --git a/substrate/srml/grandpa/Cargo.toml b/substrate/srml/grandpa/Cargo.toml
index 478cddd153..2466b8e012 100644
--- a/substrate/srml/grandpa/Cargo.toml
+++ b/substrate/srml/grandpa/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true, features = ["derive"] }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
 substrate-finality-grandpa-primitives = { path = "../../core/finality-grandpa/primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
@@ -23,7 +23,7 @@ runtime_io = { package = "sr-io", path = "../../core/sr-io" }
 default = ["std"]
 std = [
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"substrate-finality-grandpa-primitives/std",
 	"rstd/std",
diff --git a/substrate/srml/grandpa/src/lib.rs b/substrate/srml/grandpa/src/lib.rs
index 6f1c897e53..3f4b26c17d 100644
--- a/substrate/srml/grandpa/src/lib.rs
+++ b/substrate/srml/grandpa/src/lib.rs
@@ -31,7 +31,7 @@
 pub use substrate_finality_grandpa_primitives as fg_primitives;
 
 use rstd::prelude::*;
-use parity_codec::{self as codec, Encode, Decode};
+use codec::{self as codec, Encode, Decode, Error};
 use srml_support::{
 	decl_event, decl_storage, decl_module, dispatch::Result, storage::StorageValue
 };
@@ -78,11 +78,11 @@ pub struct StoredPendingChange<N> {
 }
 
 impl<N: Decode> Decode for StoredPendingChange<N> {
-	fn decode<I: codec::Input>(value: &mut I) -> Option<Self> {
+	fn decode<I: codec::Input>(value: &mut I) -> core::result::Result<Self, Error> {
 		let old = OldStoredPendingChange::decode(value)?;
 		let forced = <Option<N>>::decode(value).unwrap_or(None);
 
-		Some(StoredPendingChange {
+		Ok(StoredPendingChange {
 			scheduled_at: old.scheduled_at,
 			delay: old.delay,
 			next_authorities: old.next_authorities,
diff --git a/substrate/srml/grandpa/src/mock.rs b/substrate/srml/grandpa/src/mock.rs
index 637ae7c25f..4e5d133b9e 100644
--- a/substrate/srml/grandpa/src/mock.rs
+++ b/substrate/srml/grandpa/src/mock.rs
@@ -22,7 +22,7 @@ use sr_primitives::{Perbill, DigestItem, traits::IdentityLookup, testing::{Heade
 use runtime_io;
 use srml_support::{impl_outer_origin, impl_outer_event, parameter_types};
 use primitives::{H256, Blake2Hasher};
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use crate::{AuthorityId, GenesisConfig, Trait, Module, ConsensusLog};
 use substrate_finality_grandpa_primitives::GRANDPA_ENGINE_ID;
 
diff --git a/substrate/srml/im-online/Cargo.toml b/substrate/srml/im-online/Cargo.toml
index c015e5e4c5..60be1a89c2 100644
--- a/substrate/srml/im-online/Cargo.toml
+++ b/substrate/srml/im-online/Cargo.toml
@@ -5,7 +5,7 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
@@ -18,7 +18,7 @@ system = { package = "srml-system", path = "../system", default-features = false
 [features]
 default = ["std"]
 std = [
-	"parity-codec/std",
+	"codec/std",
 	"sr-primitives/std",
 	"rstd/std",
 	"serde",
diff --git a/substrate/srml/im-online/src/lib.rs b/substrate/srml/im-online/src/lib.rs
index 8254cb6078..19875d9a37 100644
--- a/substrate/srml/im-online/src/lib.rs
+++ b/substrate/srml/im-online/src/lib.rs
@@ -74,7 +74,7 @@ use primitives::{
 	offchain::StorageKind,
 	sr25519, ed25519,
 };
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use sr_primitives::{
 	ApplyError, traits::{Member, IsMember, Extrinsic as ExtrinsicT},
 	transaction_validity::{TransactionValidity, TransactionLongevity, ValidTransaction},
@@ -216,7 +216,7 @@ decl_module! {
 				// we run only when a local authority key is configured
 				if let Ok(key) = sr_io::pubkey(CryptoKey::AuthorityKey) {
 					let authority_id = <T as Trait>::AuthorityId::decode(&mut &key[..])
-						.ok_or(OffchainErr::DecodeAuthorityId)?;
+						.map_err(|_| OffchainErr::DecodeAuthorityId)?;
 					let network_state =
 						sr_io::network_state().map_err(|_| OffchainErr::NetworkState)?;
 					let heartbeat_data = Heartbeat {
@@ -282,7 +282,7 @@ decl_module! {
 				match last_gossip {
 					Some(last) => {
 						let worker_status: WorkerStatus<T::BlockNumber> = Decode::decode(&mut &last[..])
-							.ok_or(OffchainErr::DecodeWorkerStatus)?;
+							.map_err(|_| OffchainErr::DecodeWorkerStatus)?;
 
 						let was_aborted = !worker_status.done && worker_status.gossipping_at < now;
 
diff --git a/substrate/srml/indices/Cargo.toml b/substrate/srml/indices/Cargo.toml
index c500cf5f87..3cbf1d88de 100644
--- a/substrate/srml/indices/Cargo.toml
+++ b/substrate/srml/indices/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true }
 safe-mix = { version = "1.0", default-features = false}
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 substrate-keyring = { path = "../../core/keyring", optional = true }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 runtime-io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
@@ -25,7 +25,7 @@ std = [
 	"serde",
 	"safe-mix/std",
 	"substrate-keyring",
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"rstd/std",
 	"runtime-io/std",
diff --git a/substrate/srml/indices/src/address.rs b/substrate/srml/indices/src/address.rs
index c76585d216..caef4728fb 100644
--- a/substrate/srml/indices/src/address.rs
+++ b/substrate/srml/indices/src/address.rs
@@ -19,7 +19,8 @@
 #[cfg(feature = "std")]
 use std::fmt;
 use rstd::convert::TryInto;
-use crate::{Member, Decode, Encode, Input, Output};
+use crate::Member;
+use codec::{Encode, Decode, Input, Output, Error};
 
 /// An indices-aware address, which can be either a direct `AccountId` or
 /// an index.
@@ -54,16 +55,16 @@ impl<AccountId, AccountIndex> From<AccountId> for Address<AccountId, AccountInde
 	}
 }
 
-fn need_more_than<T: PartialOrd>(a: T, b: T) -> Option<T> {
-	if a < b { Some(b) } else { None }
+fn need_more_than<T: PartialOrd>(a: T, b: T) -> Result<T, Error> {
+	if a < b { Ok(b) } else { Err("Invalid range".into()) }
 }
 
 impl<AccountId, AccountIndex> Decode for Address<AccountId, AccountIndex> where
 	AccountId: Member + Decode,
 	AccountIndex: Member + Decode + PartialOrd<AccountIndex> + Ord + From<u32> + Copy,
 {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
-		Some(match input.read_byte()? {
+	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
+		Ok(match input.read_byte()? {
 			x @ 0x00..=0xef => Address::Index(AccountIndex::from(x as u32)),
 			0xfc => Address::Index(AccountIndex::from(
 				need_more_than(0xef, u16::decode(input)?)? as u32
@@ -75,7 +76,7 @@ impl<AccountId, AccountIndex> Decode for Address<AccountId, AccountIndex> where
 				need_more_than(0xffffffffu32.into(), Decode::decode(input)?)?
 			),
 			0xff => Address::Id(Decode::decode(input)?),
-			_ => return None,
+			_ => return Err("Invalid address variant".into()),
 		})
 	}
 }
@@ -114,6 +115,11 @@ impl<AccountId, AccountIndex> Encode for Address<AccountId, AccountIndex> where
 	}
 }
 
+impl<AccountId, AccountIndex> codec::EncodeLike for Address<AccountId, AccountIndex> where
+	AccountId: Member + Encode,
+	AccountIndex: Member + Encode + PartialOrd<AccountIndex> + Ord + Copy + From<u32> + TryInto<u32>,
+{}
+
 impl<AccountId, AccountIndex> Default for Address<AccountId, AccountIndex> where
 	AccountId: Member + Default,
 	AccountIndex: Member,
@@ -125,7 +131,7 @@ impl<AccountId, AccountIndex> Default for Address<AccountId, AccountIndex> where
 
 #[cfg(test)]
 mod tests {
-	use crate::{Encode, Decode};
+	use codec::{Encode, Decode};
 
 	type Address = super::Address<[u8; 8], u32>;
 	fn index(i: u32) -> Address { super::Address::Index(i) }
@@ -135,7 +141,7 @@ mod tests {
 		if let Some(ref a) = a {
 			assert_eq!(d, &a.encode()[..]);
 		}
-		assert_eq!(Address::decode(&mut &d[..]), a);
+		assert_eq!(Address::decode(&mut &d[..]).ok(), a);
 	}
 
 	#[test]
diff --git a/substrate/srml/indices/src/lib.rs b/substrate/srml/indices/src/lib.rs
index 0bfd6d6054..5bf838f321 100644
--- a/substrate/srml/indices/src/lib.rs
+++ b/substrate/srml/indices/src/lib.rs
@@ -20,7 +20,7 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use rstd::{prelude::*, result, marker::PhantomData, convert::TryInto};
-use parity_codec::{Encode, Decode, Codec, Input, Output};
+use codec::{Encode, Codec};
 use srml_support::{StorageValue, StorageMap, Parameter, decl_module, decl_event, decl_storage};
 use sr_primitives::traits::{One, SimpleArithmetic, StaticLookup, Member};
 use system::{IsDeadAccount, OnNewAccount};
diff --git a/substrate/srml/metadata/Cargo.toml b/substrate/srml/metadata/Cargo.toml
index cdb7a41ff8..9fc9c6e46d 100644
--- a/substrate/srml/metadata/Cargo.toml
+++ b/substrate/srml/metadata/Cargo.toml
@@ -5,7 +5,7 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 serde = { version = "1.0", optional = true, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 primitives = { package = "substrate-primitives", path = "../../core/primitives", default-features = false }
@@ -13,7 +13,7 @@ primitives = { package = "substrate-primitives", path = "../../core/primitives",
 [features]
 default = ["std"]
 std = [
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"primitives/std",
 	"serde",
diff --git a/substrate/srml/metadata/src/lib.rs b/substrate/srml/metadata/src/lib.rs
index f518de5057..329b543d1a 100644
--- a/substrate/srml/metadata/src/lib.rs
+++ b/substrate/srml/metadata/src/lib.rs
@@ -25,8 +25,8 @@
 #[cfg(feature = "std")]
 use serde::Serialize;
 #[cfg(feature = "std")]
-use parity_codec::{Decode, Input};
-use parity_codec::{Encode, Output};
+use codec::{Decode, Input, Error};
+use codec::{Encode, Output};
 use rstd::vec::Vec;
 
 #[cfg(feature = "std")]
@@ -59,11 +59,13 @@ impl<B, O> Encode for DecodeDifferent<B, O> where B: Encode + 'static, O: Encode
 	}
 }
 
+impl<B, O> codec::EncodeLike for DecodeDifferent<B, O> where B: Encode + 'static, O: Encode + 'static {}
+
 #[cfg(feature = "std")]
 impl<B, O> Decode for DecodeDifferent<B, O> where B: 'static, O: Decode + 'static {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
-		<O>::decode(input).and_then(|val| {
-			Some(DecodeDifferent::Decoded(val))
+	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
+		<O>::decode(input).map(|val| {
+			DecodeDifferent::Decoded(val)
 		})
 	}
 }
@@ -144,6 +146,8 @@ impl<E: Encode> Encode for FnEncode<E> {
 	}
 }
 
+impl<E: Encode> codec::EncodeLike for FnEncode<E> {}
+
 impl<E: Encode + PartialEq> PartialEq for FnEncode<E> {
 	fn eq(&self, other: &Self) -> bool {
 		self.0().eq(&other.0())
@@ -223,6 +227,8 @@ impl Encode for DefaultByteGetter {
 	}
 }
 
+impl codec::EncodeLike for DefaultByteGetter {}
+
 impl PartialEq<DefaultByteGetter> for DefaultByteGetter {
 	fn eq(&self, other: &DefaultByteGetter) -> bool {
 		let left = self.0.default_byte();
@@ -333,10 +339,12 @@ impl Encode for RuntimeMetadataDeprecated {
 	fn encode_to<W: Output>(&self, _dest: &mut W) {}
 }
 
+impl codec::EncodeLike for RuntimeMetadataDeprecated {}
+
 #[cfg(feature = "std")]
 impl Decode for RuntimeMetadataDeprecated {
-	fn decode<I: Input>(_input: &mut I) -> Option<Self> {
-		unimplemented!()
+	fn decode<I: Input>(_input: &mut I) -> Result<Self, Error> {
+		Err("Decoding is not supported".into())
 	}
 }
 
diff --git a/substrate/srml/session/Cargo.toml b/substrate/srml/session/Cargo.toml
index a5dfb713d1..66d47f4c35 100644
--- a/substrate/srml/session/Cargo.toml
+++ b/substrate/srml/session/Cargo.toml
@@ -7,7 +7,7 @@ edition =  "2018"
 [dependencies]
 serde = { version = "1.0", optional = true }
 safe-mix = { version = "1.0", default-features = false}
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 srml-support = { path = "../support", default-features = false }
@@ -26,7 +26,7 @@ historical = ["substrate-trie"]
 std = [
 	"serde",
 	"safe-mix/std",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"srml-support/std",
 	"sr-primitives/std",
diff --git a/substrate/srml/session/src/historical.rs b/substrate/srml/session/src/historical.rs
index 1e8e7faaaf..e35df3011c 100644
--- a/substrate/srml/session/src/historical.rs
+++ b/substrate/srml/session/src/historical.rs
@@ -26,7 +26,7 @@
 //! Afterwards, the proofs can be fed to a consensus module when reporting misbehavior.
 
 use rstd::prelude::*;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use sr_primitives::KeyTypeId;
 use sr_primitives::traits::{Convert, OpaqueKeys, Hash as HashT};
 use srml_support::{
@@ -235,13 +235,13 @@ impl<T: Trait> ProvingTrie<T> {
 		let val_idx = (key_id, key_data).using_encoded(|s| {
 			trie.get_with(s, &mut recorder)
 				.ok()?
-				.and_then(|raw| u32::decode(&mut &*raw))
+				.and_then(|raw| u32::decode(&mut &*raw).ok())
 		})?;
 
 		val_idx.using_encoded(|s| {
 			trie.get_with(s, &mut recorder)
 				.ok()?
-				.and_then(|raw| <IdentificationTuple<T>>::decode(&mut &*raw))
+				.and_then(|raw| <IdentificationTuple<T>>::decode(&mut &*raw).ok())
 		})?;
 
 		Some(recorder.drain().into_iter().map(|r| r.data).collect())
@@ -258,11 +258,11 @@ impl<T: Trait> ProvingTrie<T> {
 		let trie = TrieDB::new(&self.db, &self.root).ok()?;
 		let val_idx = (key_id, key_data).using_encoded(|s| trie.get(s))
 			.ok()?
-			.and_then(|raw| u32::decode(&mut &*raw))?;
+			.and_then(|raw| u32::decode(&mut &*raw).ok())?;
 
 		val_idx.using_encoded(|s| trie.get(s))
 			.ok()?
-			.and_then(|raw| <IdentificationTuple<T>>::decode(&mut &*raw))
+			.and_then(|raw| <IdentificationTuple<T>>::decode(&mut &*raw).ok())
 	}
 
 }
diff --git a/substrate/srml/session/src/lib.rs b/substrate/srml/session/src/lib.rs
index a189a91da2..8b9e8b1566 100644
--- a/substrate/srml/session/src/lib.rs
+++ b/substrate/srml/session/src/lib.rs
@@ -120,7 +120,7 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use rstd::{prelude::*, marker::PhantomData, ops::{Sub, Rem}};
-use parity_codec::Decode;
+use codec::Decode;
 use sr_primitives::KeyTypeId;
 use sr_primitives::weights::SimpleDispatchInfo;
 use sr_primitives::traits::{Convert, Zero, Member, OpaqueKeys, TypedKey};
diff --git a/substrate/srml/staking/Cargo.toml b/substrate/srml/staking/Cargo.toml
index 5feab0f516..5428d663f3 100644
--- a/substrate/srml/staking/Cargo.toml
+++ b/substrate/srml/staking/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true }
 safe-mix = { version = "1.0", default-features = false}
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 substrate-keyring = { path = "../../core/keyring", optional = true }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
@@ -31,7 +31,7 @@ std = [
 	"serde",
 	"safe-mix/std",
 	"substrate-keyring",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"runtime_io/std",
 	"srml-support/std",
diff --git a/substrate/srml/staking/src/lib.rs b/substrate/srml/staking/src/lib.rs
index dd540e78b1..11aa4f3c7d 100644
--- a/substrate/srml/staking/src/lib.rs
+++ b/substrate/srml/staking/src/lib.rs
@@ -284,7 +284,7 @@ mod benches;
 #[cfg(feature = "std")]
 use runtime_io::with_storage;
 use rstd::{prelude::*, result, collections::btree_map::BTreeMap};
-use parity_codec::{HasCompact, Encode, Decode};
+use codec::{HasCompact, Encode, Decode};
 use srml_support::{
 	StorageValue, StorageMap, EnumerableStorageMap, decl_module, decl_event,
 	decl_storage, ensure, traits::{
diff --git a/substrate/srml/sudo/Cargo.toml b/substrate/srml/sudo/Cargo.toml
index 6f7d290396..d0e2d5dbc5 100644
--- a/substrate/srml/sudo/Cargo.toml
+++ b/substrate/srml/sudo/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 sr-std = { path = "../../core/sr-std", default-features = false }
 sr-io = { path = "../../core/sr-io", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
@@ -22,7 +22,7 @@ primitives = { package = "substrate-primitives",  path = "../../core/primitives"
 default = ["std"]
 std = [
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"sr-std/std",
 	"sr-io/std",
 	"sr-primitives/std",
diff --git a/substrate/srml/support/Cargo.toml b/substrate/srml/support/Cargo.toml
index 99fa2dbb38..2befc11b19 100644
--- a/substrate/srml/support/Cargo.toml
+++ b/substrate/srml/support/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true, features = ["derive"] }
-codec = { package = "parity-codec", version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 srml-metadata = { path = "../metadata", default-features = false }
 sr-std = { path = "../../core/sr-std", default-features = false }
 runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
diff --git a/substrate/srml/support/src/storage/hashed/generator.rs b/substrate/srml/support/src/storage/hashed/generator.rs
index 4d367fb2a8..19c4440c85 100644
--- a/substrate/srml/support/src/storage/hashed/generator.rs
+++ b/substrate/srml/support/src/storage/hashed/generator.rs
@@ -208,7 +208,7 @@ pub trait StorageValue<T: codec::Codec> {
 		let new_val = <T as codec::EncodeAppend>::append(
 			storage.get_raw(Self::key()).unwrap_or_default(),
 			items,
-		).ok_or_else(|| "Could not append given item")?;
+		).map_err(|_| "Could not append given item")?;
 		storage.put_raw(Self::key(), &new_val);
 		Ok(())
 	}
@@ -286,7 +286,7 @@ pub trait AppendableStorageMap<K: codec::Codec, V: codec::Codec>: StorageMap<K,
 		let new_val = <V as codec::EncodeAppend>::append(
 			storage.get_raw(&k[..]).unwrap_or_default(),
 			items,
-		).ok_or_else(|| "Could not append given item")?;
+		).map_err(|_| "Could not append given item")?;
 		storage.put_raw(&k[..], &new_val);
 		Ok(())
 	}
diff --git a/substrate/srml/support/src/storage/unhashed/generator.rs b/substrate/srml/support/src/storage/unhashed/generator.rs
index 26cb4b73e5..a5385af8fb 100644
--- a/substrate/srml/support/src/storage/unhashed/generator.rs
+++ b/substrate/srml/support/src/storage/unhashed/generator.rs
@@ -234,7 +234,7 @@ pub trait StorageDoubleMap<K1: codec::Encode, K2: codec::Encode, V: codec::Codec
 		let new_val = <V as codec::EncodeAppend>::append(
 			storage.get_raw(&key).unwrap_or_default(),
 			items,
-		).ok_or_else(|| "Could not append given item")?;
+		).map_err(|_| "Could not append given item")?;
 		storage.put_raw(&key, &new_val);
 		Ok(())
 	}
diff --git a/substrate/srml/support/test/Cargo.toml b/substrate/srml/support/test/Cargo.toml
index a4152dae2f..fa3a04d3bc 100644
--- a/substrate/srml/support/test/Cargo.toml
+++ b/substrate/srml/support/test/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", default-features = false, features = ["derive"] }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 runtime_io = { package = "sr-io", path = "../../../core/sr-io", default-features = false }
 srml-support = { version = "2", path = "../", default-features = false }
 inherents = { package = "substrate-inherents", path = "../../../core/inherents", default-features = false }
@@ -18,7 +18,7 @@ pretty_assertions = "0.6.1"
 default = ["std"]
 std = [
 	"serde/std",
-	"parity-codec/std",
+	"codec/std",
 	"runtime_io/std",
 	"srml-support/std",
 	"inherents/std",
diff --git a/substrate/srml/support/test/tests/final_keys.rs b/substrate/srml/support/test/tests/final_keys.rs
index 54c08d5e5f..0b16db3de7 100644
--- a/substrate/srml/support/test/tests/final_keys.rs
+++ b/substrate/srml/support/test/tests/final_keys.rs
@@ -17,7 +17,7 @@
 use runtime_io::{with_externalities, Blake2Hasher};
 use srml_support::{StorageValue, StorageMap, StorageDoubleMap};
 use srml_support::storage::unhashed;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 
 pub trait Trait {
 	type Origin;
diff --git a/substrate/srml/support/test/tests/genesisconfig.rs b/substrate/srml/support/test/tests/genesisconfig.rs
index 717c7105b5..b190fa8b74 100644
--- a/substrate/srml/support/test/tests/genesisconfig.rs
+++ b/substrate/srml/support/test/tests/genesisconfig.rs
@@ -15,7 +15,7 @@
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
 pub trait Trait {
-    type BlockNumber: parity_codec::Codec + Default;
+    type BlockNumber: codec::Codec + Default;
     type Origin;
 }
 
@@ -41,4 +41,4 @@ fn init_genesis_config() {
 	GenesisConfig::<Test> {
 		t: Default::default(),
 	};
-}
\ No newline at end of file
+}
diff --git a/substrate/srml/support/test/tests/instance.rs b/substrate/srml/support/test/tests/instance.rs
index 863532ff09..f77b4a284a 100644
--- a/substrate/srml/support/test/tests/instance.rs
+++ b/substrate/srml/support/test/tests/instance.rs
@@ -45,7 +45,7 @@ mod module1 {
 		type Event: From<Event<Self, I>> + Into<<Self as system::Trait>::Event>;
 		type Origin: From<Origin<Self, I>>;
 		type SomeParameter: Get<u32>;
-		type GenericType: Default + Clone + parity_codec::Codec;
+		type GenericType: Default + Clone + codec::Codec;
 	}
 
 	srml_support::decl_module! {
diff --git a/substrate/srml/system/Cargo.toml b/substrate/srml/system/Cargo.toml
index 35ddfabd6e..9816555621 100644
--- a/substrate/srml/system/Cargo.toml
+++ b/substrate/srml/system/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 [dependencies]
 serde = { version = "1.0", optional = true, features = ["derive"] }
 safe-mix = { version = "1.0", default-features = false}
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
@@ -22,7 +22,7 @@ default = ["std"]
 std = [
 	"serde",
 	"safe-mix/std",
-	"parity-codec/std",
+	"codec/std",
 	"primitives/std",
 	"rstd/std",
 	"runtime_io/std",
diff --git a/substrate/srml/system/src/lib.rs b/substrate/srml/system/src/lib.rs
index ac8357f5ca..d3a87cd38b 100644
--- a/substrate/srml/system/src/lib.rs
+++ b/substrate/srml/system/src/lib.rs
@@ -95,7 +95,7 @@ use srml_support::{
 	Parameter, for_each_tuple, traits::{Contains, Get}
 };
 use safe_mix::TripletMix;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 
 #[cfg(any(feature = "std", test))]
 use runtime_io::{twox_128, TestExternalities, Blake2Hasher};
@@ -140,8 +140,8 @@ impl<AccountId> IsDeadAccount<AccountId> for () {
 }
 
 /// Compute the trie root of a list of extrinsics.
-pub fn extrinsics_root<H: Hash, E: parity_codec::Encode>(extrinsics: &[E]) -> H::Output {
-	extrinsics_data_root::<H>(extrinsics.iter().map(parity_codec::Encode::encode).collect())
+pub fn extrinsics_root<H: Hash, E: codec::Encode>(extrinsics: &[E]) -> H::Output {
+	extrinsics_data_root::<H>(extrinsics.iter().map(codec::Encode::encode).collect())
 }
 
 /// Compute the trie root of a list of extrinsics.
@@ -412,7 +412,7 @@ decl_storage! {
 			_: &mut sr_primitives::ChildrenStorageOverlay,
 			config: &GenesisConfig|
 		{
-			use parity_codec::Encode;
+			use codec::Encode;
 
 			storage.insert(well_known_keys::CODE.to_vec(), config.code.clone());
 			storage.insert(well_known_keys::EXTRINSIC_INDEX.to_vec(), 0u32.encode());
diff --git a/substrate/srml/timestamp/Cargo.toml b/substrate/srml/timestamp/Cargo.toml
index 765573ce46..9b066a1505 100644
--- a/substrate/srml/timestamp/Cargo.toml
+++ b/substrate/srml/timestamp/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 inherents = { package = "substrate-inherents", path = "../../core/inherents", default-features = false }
@@ -21,7 +21,7 @@ primitives = { package = "substrate-primitives",  path = "../../core/primitives"
 default = ["std"]
 std = [
 	"inherents/std",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"sr-primitives/std",
 	"srml-support/std",
diff --git a/substrate/srml/timestamp/src/lib.rs b/substrate/srml/timestamp/src/lib.rs
index cc439da8ee..bc9533e6e6 100644
--- a/substrate/srml/timestamp/src/lib.rs
+++ b/substrate/srml/timestamp/src/lib.rs
@@ -91,9 +91,9 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use rstd::{result, ops::{Mul, Div}, cmp};
-use parity_codec::Encode;
+use codec::Encode;
 #[cfg(feature = "std")]
-use parity_codec::Decode;
+use codec::Decode;
 #[cfg(feature = "std")]
 use inherents::ProvideInherentData;
 use srml_support::{StorageValue, Parameter, decl_storage, decl_module, for_each_tuple};
@@ -133,7 +133,7 @@ impl InherentError {
 	#[cfg(feature = "std")]
 	pub fn try_from(id: &InherentIdentifier, data: &[u8]) -> Option<Self> {
 		if id == &INHERENT_IDENTIFIER {
-			<InherentError as parity_codec::Decode>::decode(&mut &data[..])
+			<InherentError as codec::Decode>::decode(&mut &data[..]).ok()
 		} else {
 			None
 		}
diff --git a/substrate/srml/treasury/Cargo.toml b/substrate/srml/treasury/Cargo.toml
index 4314d959b3..ae2681e11b 100644
--- a/substrate/srml/treasury/Cargo.toml
+++ b/substrate/srml/treasury/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 serde = { version = "1.0", optional = true, features = ["derive"] }
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 srml-support = { path = "../support", default-features = false }
@@ -21,7 +21,7 @@ primitives = { package = "substrate-primitives",  path = "../../core/primitives"
 default = ["std"]
 std = [
 	"serde",
-	"parity-codec/std",
+	"codec/std",
 	"rstd/std",
 	"sr-primitives/std",
 	"srml-support/std",
diff --git a/substrate/srml/treasury/src/lib.rs b/substrate/srml/treasury/src/lib.rs
index 702fe3048e..1cf3277199 100644
--- a/substrate/srml/treasury/src/lib.rs
+++ b/substrate/srml/treasury/src/lib.rs
@@ -80,7 +80,7 @@ use sr_primitives::traits::{
 	Zero, EnsureOrigin, StaticLookup, CheckedSub, CheckedMul, AccountIdConversion
 };
 use sr_primitives::weights::SimpleDispatchInfo;
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use system::ensure_signed;
 
 type BalanceOf<T> = <<T as Trait>::Currency as Currency<<T as system::Trait>::AccountId>>::Balance;
diff --git a/substrate/subkey/Cargo.toml b/substrate/subkey/Cargo.toml
index 3e0079cedf..da97ace38e 100644
--- a/substrate/subkey/Cargo.toml
+++ b/substrate/subkey/Cargo.toml
@@ -17,7 +17,7 @@ substrate-bip39 = "0.2.2"
 schnorrkel = "0.1.1"
 hex = "0.3"
 hex-literal = "0.2"
-parity-codec = "4.1.1"
+codec = { package = "parity-scale-codec", version = "1.0.0" }
 system = { package = "srml-system", path = "../srml/system" }
 balances = { package = "srml-balances", path = "../srml/balances" }
 
diff --git a/substrate/subkey/src/main.rs b/substrate/subkey/src/main.rs
index 4a63138bf6..c123e88ec2 100644
--- a/substrate/subkey/src/main.rs
+++ b/substrate/subkey/src/main.rs
@@ -26,7 +26,7 @@ use primitives::{
 	ed25519, sr25519, hexdisplay::HexDisplay, Pair, Public, blake2_256,
 	crypto::{Ss58Codec, set_default_ss58_version, Ss58AddressFormat}
 };
-use parity_codec::{Encode, Decode};
+use codec::{Encode, Decode};
 use sr_primitives::generic::Era;
 use node_primitives::{Balance, Index, Hash};
 use node_runtime::{Call, UncheckedExtrinsic, BalancesCall, Runtime};
@@ -165,7 +165,7 @@ fn execute<C: Crypto>(matches: clap::ArgMatches) where
 			let genesis_hash: Hash = match matches.value_of("genesis").unwrap_or("alex") {
 				"elm" => hex!["10c08714a10c7da78f40a60f6f732cf0dba97acfb5e2035445b032386157d5c3"].into(),
 				"alex" => hex!["dcd1346701ca8396496e52aa2785b1748deb6db09551b72159dcb3e08991025b"].into(),
-				h => hex::decode(h).ok().and_then(|x| Decode::decode(&mut &x[..]))
+				h => hex::decode(h).ok().and_then(|x| Decode::decode(&mut &x[..]).ok())
 					.expect("Invalid genesis hash or unrecognised chain identifier"),
 			};
 
@@ -203,12 +203,12 @@ fn execute<C: Crypto>(matches: clap::ArgMatches) where
 			let call = matches.value_of("call")
 				.expect("call is required; thus it can't be None; qed");
 			let function: Call = hex::decode(&call).ok()
-				.and_then(|x| Decode::decode(&mut &x[..])).unwrap();
+				.and_then(|x| Decode::decode(&mut &x[..]).ok()).unwrap();
 
 			let genesis_hash: Hash = match matches.value_of("genesis").unwrap_or("alex") {
 				"elm" => hex!["10c08714a10c7da78f40a60f6f732cf0dba97acfb5e2035445b032386157d5c3"].into(),
 				"alex" => hex!["dcd1346701ca8396496e52aa2785b1748deb6db09551b72159dcb3e08991025b"].into(),
-				h => hex::decode(h).ok().and_then(|x| Decode::decode(&mut &x[..]))
+				h => hex::decode(h).ok().and_then(|x| Decode::decode(&mut &x[..]).ok())
 					.expect("Invalid genesis hash or unrecognised chain identifier"),
 			};
 
@@ -289,7 +289,7 @@ mod tests {
 	fn should_work() {
 		let s = "0123456789012345678901234567890123456789012345678901234567890123";
 
-		let d1: Hash = hex::decode(s).ok().and_then(|x| Decode::decode(&mut &x[..])).unwrap();
+		let d1: Hash = hex::decode(s).ok().and_then(|x| Decode::decode(&mut &x[..]).ok()).unwrap();
 
 		let d2: Hash = {
 			let mut gh: [u8; 32] = Default::default();
diff --git a/substrate/test-utils/transaction-factory/Cargo.toml b/substrate/test-utils/transaction-factory/Cargo.toml
index 1c4cf5a5d5..f3c392c3d6 100644
--- a/substrate/test-utils/transaction-factory/Cargo.toml
+++ b/substrate/test-utils/transaction-factory/Cargo.toml
@@ -9,7 +9,7 @@ cli = { package = "substrate-cli", path = "../../core/cli" }
 client = { package = "substrate-client", path = "../../core/client" }
 consensus_common = { package = "substrate-consensus-common", path = "../../core/consensus/common" }
 log = "0.4"
-parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 primitives = { package = "substrate-primitives", path = "../../core/primitives", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 substrate-service = { path = "../../core/service" }
@@ -17,6 +17,6 @@ substrate-service = { path = "../../core/service" }
 [features]
 default = ["std"]
 std = [
-	"parity-codec/std",
+	"codec/std",
 	"sr-primitives/std",
 ]
diff --git a/substrate/test-utils/transaction-factory/src/lib.rs b/substrate/test-utils/transaction-factory/src/lib.rs
index 11b080f14f..ab7dfb8cea 100644
--- a/substrate/test-utils/transaction-factory/src/lib.rs
+++ b/substrate/test-utils/transaction-factory/src/lib.rs
@@ -33,7 +33,7 @@ use consensus_common::{
 	SelectChain
 };
 use consensus_common::block_import::BlockImport;
-use parity_codec::{Decode, Encode};
+use codec::{Decode, Encode};
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{
 	Block as BlockT, Header as HeaderT, ProvideRuntimeApi, SimpleArithmetic,