eth_getCode - Flashblocks

Example code for the eth_getCode JSON-RPC method. Complete guide on how to use eth_getCode JSON-RPC in GetBlock Web3 documentation.

The eth_getCode method returns the bytecode at a given address. This is used to determine if an address is a smart contract and to retrieve the deployed contract code. When the block reference is "pending", Flashblocks detect contract deployments before the block seals.

Parameters

Parameter	Type	Required	Description
address	string	Yes	20-byte address to check
blockParameter	string	Yes	Block number in hex, or "pending"

Request

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "eth_getCode",
    "params": [
    "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "pending",
    ]
    "id": "getblock.io"
}'

Axios (JavaScript)

const axios = require('axios');

const response = await axios.post('https://go.getblock.io/<ACCESS-TOKEN>/', {
    jsonrpc: '2.0',
    method: 'eth_getCode',
    params: [
    '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
    'pending'],
    id: 'getblock.io'
}, {
    headers: { 'Content-Type': 'application/json' }
});

const code = response.data.result;
const isContract = code !== '0x';
console.log('Is Contract:', isContract);
console.log('Code Length:', (code.length - 2) / 2, 'bytes');

Requests (Python)

import requests

response = requests.post(
    'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'eth_getCode',
        'params': [
    '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
    'pending'],
        'id': 'getblock.io'
    }
)

result = response.json()
code = result['result']
is_contract = code != '0x'
print(f'Is Contract: {is_contract}')
print(f'Code Length: {(len(code) - 2) // 2} bytes')

Rust

use reqwest::Client;
use serde_json::{json, Value};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();
    
    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "eth_getCode",
            "params": [
    "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "pending"],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;
    
    let code = response["result"].as_str().unwrap();
    let is_contract = code != "0x";
    println!("Is Contract: {}", is_contract);
    Ok(())
}

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x608060405234801561001057600080fd5b50..."
}

Response Parameters

Parameter	Type	Description
jsonrpc	string	JSON-RPC protocol version ("2.0")
id	string	Request identifier matching the request
result	string	Bytecode at the address (hex). Returns "0x" for EOAs

Use Cases

• Contract Detection: Verify if address is a smart contract

• Security Analysis: Examine contract bytecode for vulnerabilities

• Contract Verification: Compare deployed code with source

• Proxy Detection: Identify proxy patterns in bytecode

• Contract Indexing: Catalog deployed contracts

Error Handling

Error Code	Message	Description
-32602	Invalid params	Invalid address format
-32603	Internal error	Node internal failure

SDK Integration

ethers.js

import { ethers } from 'ethers';

const provider = new ethers.JsonRpcProvider('https://go.getblock.io/<ACCESS-TOKEN>/');

// Generic JSON-RPC call — 'pending' returns Flashblocks-preconfirmed state:
const result = await provider.send('eth_code', [
    "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "pending"]);
console.log(result);

viem

import { createPublicClient, http } from 'viem';

const client = createPublicClient({
    transport: http('https://go.getblock.io/<ACCESS-TOKEN>/')
});

// viem's read methods accept blockTag: 'pending' for Flashblocks-preconfirmed state:
const result = await client.request({
    method: 'eth_code',
    params: [
    "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "pending"]
});
console.log(result);

// Typed wrappers also accept blockTag: 'pending':
// client.getBlock({ blockTag: 'pending' })