chain_getFinalizedHead - Bittensor

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

Returns the hash of the latest finalized block. Finalized blocks in Substrate are guaranteed not to be reorged — this is the safe reference for confirmed transaction reads.

Substrate native JSON-RPC method. Call against a GetBlock endpoint configured for the Substrate interface. For typed SDK access, use Polkadot.js (TypeScript) or substrateinterface (Python).

Parameters

• None

Request Example

cURL

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

JavaScript (Axios)

import axios from 'axios';

const data = JSON.stringify({
    "jsonrpc": "2.0",
    "method": "chain_getFinalizedHead",
    "params": [],
    "id": "getblock.io"
});

const config = {
    method: 'post',
    url: 'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers: {
        'Content-Type': 'application/json'
    },
    data: data
};

axios(config)
    .then(response => console.log(JSON.stringify(response.data, null, 2)))
    .catch(error => console.log(error));

Python (Requests)

import requests
import json

url = "https://go.getblock.io/<ACCESS-TOKEN>/"

payload = json.dumps({
    "jsonrpc": "2.0",
    "method": "chain_getFinalizedHead",
    "params": [],
    "id": "getblock.io"
})

headers = {
    'Content-Type': 'application/json'
}

response = requests.post(url, headers=headers, data=payload)
print(response.text)

Rust (Reqwest)

use reqwest::Client;
use serde_json::json;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();

    let payload = json!({
        "jsonrpc": "2.0",
        "method": "chain_getFinalizedHead",
        "params": [],
        "id": "getblock.io"
});

    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&payload)
        .send()
        .await?;

    let result: serde_json::Value = response.json().await?;
    println!("{:#?}", result);

    Ok(())
}

Response Example

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0xc0a6cfca5d4f9e1cb8a5c4b3d2e7a9c4f1b8e6d5c3a2b1f9e8d7c6b5a4f3e2d1c"
}

Response Parameters

Field	Type	Description
result	string	Block hash of the latest finalized block

Use Cases

• Reading state at a guaranteed-final reference point

• Indexer cursor — only process blocks up to the finalized head to avoid reorgs

• Building safe withdrawal logic that waits for finality before crediting

Error Handling

Status Code	Error Message	Cause
403	Forbidden	Missing or invalid <ACCESS-TOKEN>
-32602	Invalid params	Request parameters are missing or malformed
-32601	Method not found	Method does not exist on this interface — check whether you're calling a Substrate method on an EVM endpoint or vice versa
-32603	Internal error	Server-side error while processing the request
429	Too Many Requests	Rate limit exceeded for your plan

SDK Integration

Polkadot.js (TypeScript)

import { ApiPromise, WsProvider } from '@polkadot/api';

const provider = new WsProvider('wss://go.getblock.io/<ACCESS-TOKEN>/');
const api = await ApiPromise.create({ provider });

// Typed wrapper: api.rpc.chain.getFinalizedHead(...)
const result = await api.rpc.chain.getFinalizedHead();
console.log(result.toHuman());

// Or use the raw RPC interface for any method:
// const raw = await api.rpc.send({ method: 'chain_getFinalizedHead', params: [] });

substrateinterface (Python)

from substrateinterface import SubstrateInterface

substrate = SubstrateInterface(url="wss://go.getblock.io/<ACCESS-TOKEN>/")

# Generic RPC call:
result = substrate.rpc_request("chain_getFinalizedHead", [])
print(result)