starknet_getClassAt - STRK

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

This method returns the class definition of the contract deployed at a given address at a block, resolving the class hash for you. It combines class-hash lookup and class fetch.

Parameters

Parameter	Type	Required	Description
block_id	object | string	Yes	{block_number} or {block_hash}, or a tag
contract_address	string	Yes	The contract address to resolve and fetch

Request

cURL

curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "starknet_getClassAt",
    "params": ["latest", "0x049d36570d4e46f48e99674bd3fcc84644ddd6b96f7c741b1562b82f9e004dc7"],
    "id": "getblock.io"
}'

Axios

example.js

const axios = require('axios');

const response = await axios.post('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', {
    jsonrpc: '2.0',
    method: 'starknet_getClassAt',
    params: ['latest', '0x049d36570d4e46f48e99674bd3fcc84644ddd6b96f7c741b1562b82f9e004dc7'],
    id: 'getblock.io'
}, {
    headers: { 'Content-Type': 'application/json' }
});

console.log(response.data.result);

Request

example.py

import requests

response = requests.post(
    'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'starknet_getClassAt',
        'params': ['latest', '0x049d36570d4e46f48e99674bd3fcc84644ddd6b96f7c741b1562b82f9e004dc7'],
        'id': 'getblock.io'
    }
)

print(response.json())

Rust

example.rs

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://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "starknet_getClassAt",
            "params": ["latest", "0x049d36570d4e46f48e99674bd3fcc84644ddd6b96f7c741b1562b82f9e004dc7"],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;

    println!("Result: {}", response["result"]);
    Ok(())
}

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": {
        "contract_class_version": "0.1.0",
        "sierra_program": [
            "0x1",
            "0x3",
            "0x..."
        ],
        "entry_points_by_type": {
            "EXTERNAL": [
                {
                    "selector": "0x2e4263afad30923c891518314c3c95dbe830a16874e8abc5777a9a20b54c76e",
                    "function_idx": 0
                }
            ],
            "L1_HANDLER": [],
            "CONSTRUCTOR": []
        },
        "abi": "[{\"type\":\"function\",\"name\":\"balanceOf\"}]"
    }
}

Response Parameters

Parameter	Type	Description
jsonrpc	string	JSON-RPC protocol version ("2.0")
id	string	Request identifier matching the request
result	object	Class definition of the deployed contract

Use Cases

• One-Call ABI: Fetch a deployed contract's ABI by address

• Interface Discovery: Enumerate entry points for an address

• Tooling: Load code and ABI directly from an address

• Verification: Confirm a deployed contract's class contents

Error Handling

Error	Message	Description
20 / CONTRACT_NOT_FOUND	Contract not found	No contract exists at the address at that block
24 / BLOCK_NOT_FOUND	Block not found	No block matches the supplied block_id