starknet_getClass - STRK

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

This method returns the class definition — the Sierra program, entry points, and ABI — for a given class hash at a block. It is used to load a contract's interface and code.

Parameters

Parameter	Type	Required	Description
block_id	object | string	Yes	{block_number} or {block_hash}, or a tag
class_hash	string	Yes	The class hash to 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_getClass",
    "params": ["latest", "0x01a736d6ed154502257f02b1ccdf4d9d1089f80811cd6acad48e6b6a9d1f2003"],
    "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_getClass',
    params: ['latest', '0x01a736d6ed154502257f02b1ccdf4d9d1089f80811cd6acad48e6b6a9d1f2003'],
    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_getClass',
        'params': ['latest', '0x01a736d6ed154502257f02b1ccdf4d9d1089f80811cd6acad48e6b6a9d1f2003'],
        '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_getClass",
            "params": ["latest", "0x01a736d6ed154502257f02b1ccdf4d9d1089f80811cd6acad48e6b6a9d1f2003"],
            "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 (see fields below)

Result Object

Field	Type	Description
sierra_program	array	The Sierra bytecode of the class
entry_points_by_type	object	External, L1 handler, and constructor entry points
abi	string	JSON ABI string describing the class interface

Use Cases

• ABI Loading: Load a contract's ABI to encode calls

• Class Verification: Compare a class definition against a known build

• Tooling: Feed Sierra/ABI into analysis or codegen tools

• Interface Discovery: Enumerate a contract's entry points

Error Handling

Error	Message	Description
28 / CLASS_HASH_NOT_FOUND	Class hash not found	No class matches the supplied hash at that block
24 / BLOCK_NOT_FOUND	Block not found	No block matches the supplied block_id