diff --git a/crates/integration/contracts/ExtCode.sol b/crates/integration/contracts/ExtCode.sol
new file mode 100644
index 0000000..89249c9
--- /dev/null
+++ b/crates/integration/contracts/ExtCode.sol
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8;
+
+contract ExtCode {
+    function ExtCodeSize(address who) public view returns (uint ret) {
+        assembly {
+            ret := extcodesize(who)
+        }
+    }
+}
diff --git a/crates/integration/src/cases.rs b/crates/integration/src/cases.rs
index 6abd94c..19c1f75 100644
--- a/crates/integration/src/cases.rs
+++ b/crates/integration/src/cases.rs
@@ -1,4 +1,4 @@
-use alloy_primitives::{I256, U256};
+use alloy_primitives::{Address, I256, U256};
 use alloy_sol_types::{sol, SolCall, SolConstructor};
 
 use crate::mock_runtime::{CallOutput, State};
@@ -123,6 +123,12 @@ sol!(
     }
 );
 
+sol!(
+    contract ExtCode {
+        function ExtCodeSize(address who) public view returns (uint ret);
+    }
+);
+
 impl Contract {
     /// Execute the contract.
     ///
@@ -405,6 +411,18 @@ impl Contract {
             calldata: vec![0; 4],
         }
     }
+
+    pub fn ext_code_size(address: Address) -> Self {
+        let code = include_str!("../contracts/ExtCode.sol");
+        let name = "ExtCode";
+
+        Self {
+            name,
+            evm_runtime: crate::compile_evm_bin_runtime(name, code),
+            pvm_runtime: crate::compile_blob(name, code),
+            calldata: ExtCode::ExtCodeSizeCall::new((address,)).abi_encode(),
+        }
+    }
 }
 
 #[cfg(test)]
diff --git a/crates/integration/src/mock_runtime.rs b/crates/integration/src/mock_runtime.rs
index a380983..e29828f 100644
--- a/crates/integration/src/mock_runtime.rs
+++ b/crates/integration/src/mock_runtime.rs
@@ -730,6 +730,30 @@ fn link_host_functions(engine: &Engine) -> Linker<Transaction> {
         )
         .unwrap();
 
+    linker
+        .func_wrap(
+            runtime_api::CODE_SIZE,
+            |caller: Caller<Transaction>, address_ptr: u32| {
+                let (caller, transaction) = caller.split();
+
+                let bytes = caller.read_memory_into_vec(address_ptr, 32)?;
+                let word = U256::from_le_slice(&bytes);
+                let address = Address::from_word(word.into());
+
+                log::info!("{}", address);
+
+                Ok(transaction
+                    .state
+                    .accounts
+                    .get(&address)
+                    .and_then(|account| account.contract)
+                    .and_then(|blob_hash| transaction.state.blobs.get(&blob_hash))
+                    .map(|code| code.len())
+                    .unwrap_or_default() as u32)
+            },
+        )
+        .unwrap();
+
     linker
 }
 
diff --git a/crates/integration/src/tests.rs b/crates/integration/src/tests.rs
index c746433..96916c6 100644
--- a/crates/integration/src/tests.rs
+++ b/crates/integration/src/tests.rs
@@ -507,3 +507,18 @@ fn create_with_value() {
         }
     }
 }
+
+#[test]
+fn ext_code_size() {
+    let contract = Contract::ext_code_size(Transaction::default_address());
+    let (_, output) = assert_success(&contract, false);
+    let received = U256::from_be_slice(&output.data);
+    let expected = U256::from(contract.pvm_runtime.len());
+    assert_eq!(received, expected);
+
+    let contract = Contract::ext_code_size(Default::default());
+    let (_, output) = assert_success(&contract, false);
+    let received = U256::from_be_slice(&output.data);
+    let expected = U256::ZERO;
+    assert_eq!(received, expected);
+}
diff --git a/crates/llvm-context/src/polkavm/const/runtime_api.rs b/crates/llvm-context/src/polkavm/const/runtime_api.rs
index 3f9891d..c4c4b61 100644
--- a/crates/llvm-context/src/polkavm/const/runtime_api.rs
+++ b/crates/llvm-context/src/polkavm/const/runtime_api.rs
@@ -16,6 +16,8 @@ pub static BLOCK_NUMBER: &str = "block_number";
 
 pub static CALLER: &str = "caller";
 
+pub static CODE_SIZE: &str = "code_size";
+
 pub static DEPOSIT_EVENT: &str = "deposit_event";
 
 pub static GET_STORAGE: &str = "get_storage";
@@ -36,7 +38,7 @@ pub static VALUE_TRANSFERRED: &str = "value_transferred";
 
 /// All imported runtime API symbols..
 /// Useful for configuring common attributes and linkage.
-pub static IMPORTS: [&str; 11] = [
+pub static IMPORTS: [&str; 12] = [
     ADDRESS,
     BLOCK_NUMBER,
     CALLER,
@@ -44,6 +46,7 @@ pub static IMPORTS: [&str; 11] = [
     GET_STORAGE,
     HASH_KECCAK_256,
     INPUT,
+    INSTANTIATE,
     NOW,
     RETURN,
     SET_STORAGE,
diff --git a/crates/llvm-context/src/polkavm/evm/ext_code.rs b/crates/llvm-context/src/polkavm/evm/ext_code.rs
index 7d7c66a..ae619ab 100644
--- a/crates/llvm-context/src/polkavm/evm/ext_code.rs
+++ b/crates/llvm-context/src/polkavm/evm/ext_code.rs
@@ -1,17 +1,36 @@
 //! Translates the external code operations.
 
+use inkwell::values::BasicValue;
+
 use crate::polkavm::context::Context;
 use crate::polkavm::Dependency;
+use crate::polkavm_const::runtime_api;
 
 /// Translates the `extcodesize` instruction.
 pub fn size<'ctx, D>(
-    _context: &mut Context<'ctx, D>,
-    _address: inkwell::values::IntValue<'ctx>,
+    context: &mut Context<'ctx, D>,
+    address: inkwell::values::IntValue<'ctx>,
 ) -> anyhow::Result<inkwell::values::BasicValueEnum<'ctx>>
 where
     D: Dependency + Clone,
 {
-    todo!()
+    let address_pointer = context.build_alloca(context.word_type(), "value");
+    context.build_store(address_pointer, address)?;
+
+    let address_pointer_casted = context.builder().build_ptr_to_int(
+        address_pointer.value,
+        context.xlen_type(),
+        "address_pointer",
+    )?;
+    let value = context
+        .build_runtime_call(runtime_api::CODE_SIZE, &[address_pointer_casted.into()])
+        .unwrap_or_else(|| panic!("{} should return a value", runtime_api::CODE_SIZE))
+        .into_int_value();
+
+    Ok(context
+        .builder()
+        .build_int_z_extend(value, context.word_type(), "extcodesize")?
+        .as_basic_value_enum())
 }
 
 /// Translates the `extcodehash` instruction.
diff --git a/crates/pallet-contracts-pvm-llapi/src/polkavm_guest.c b/crates/pallet-contracts-pvm-llapi/src/polkavm_guest.c
index dc92241..0317ba3 100644
--- a/crates/pallet-contracts-pvm-llapi/src/polkavm_guest.c
+++ b/crates/pallet-contracts-pvm-llapi/src/polkavm_guest.c
@@ -73,6 +73,8 @@ POLKAVM_IMPORT(uint32_t, is_contract, uint32_t)
 
 POLKAVM_IMPORT(uint32_t, code_hash, uint32_t, uint32_t, uint32_t)
 
+POLKAVM_IMPORT(uint32_t, code_size, uint32_t)
+
 POLKAVM_IMPORT(void, own_code_hash, uint32_t, uint32_t)
 
 POLKAVM_IMPORT(uint32_t, caller_is_origin)
diff --git a/crates/solidity/src/solc/standard_json/output/error/mod.rs b/crates/solidity/src/solc/standard_json/output/error/mod.rs
index 80311ee..d8ef002 100644
--- a/crates/solidity/src/solc/standard_json/output/error/mod.rs
+++ b/crates/solidity/src/solc/standard_json/output/error/mod.rs
@@ -87,9 +87,9 @@ impl Error {
 │ usually needed in the following cases:                                                           │
 │   1. To detect whether an address belongs to a smart contract.                                   │
 │   2. To detect whether the deploy code execution has finished.                                   │
-│ zkSync Era comes with native account abstraction support (so accounts are smart contracts,       │
-│ including private-key controlled EOAs), and you should avoid differentiating between contracts   │
-│ and non-contract addresses.                                                                      │
+│ Polkadot comes with native account abstraction support (so smart contracts are just accounts     │
+│ coverned by code), and you should avoid differentiating between contracts and non-contract       |
+| addresses.                                                                                       │
 └──────────────────────────────────────────────────────────────────────────────────────────────────┘"#
             .to_owned();