chain_getFinalizedHead - Polkadot

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

This method returns the hash of the most recently finalized block. Finalized blocks are irreversible under GRANDPA finality.

Parameters

This method does not accept any parameters.

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": "chain_getFinalizedHead", "params": [], "id": "getblock.io"}'

JavaScript

example.js

const response = await fetch('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
        jsonrpc: '2.0',
        method: 'chain_getFinalizedHead',
        params: [],
        id: 'getblock.io'
    })
});

const data = await response.json();
console.log(data.result);

Python

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': 'chain_getFinalizedHead',
        'params': [],
        'id': 'getblock.io'
    }
)

print(response.json()['result'])

Response

{
    "id": "getblock.io",
    "jsonrpc": "2.0",
    "result": "0x255bc00927df8d33d561792635cbc6bde480a0a505eef5ff28630ece3fc15b32"
}

Response Parameters

Parameter	Type	Description
id	string	Request identifier matching the request
jsonrpc	string	JSON-RPC protocol version ("2.0")
result	string	Hash of the latest finalized block header

Use Cases

• Finality Checks: Read the latest irreversible block for settlement

• Safe Confirmations: Confirm a transaction is below the finalized head

• Reorg Safety: Anchor reads to finalized state to avoid reorgs

• Bridges: Prove finalized state to another chain

Error Handling

Error Code	Message	Description
-32602	Invalid params	A parameter is missing or has the wrong type or format
-32601	Method not found	The method is not available on this endpoint
-32603	Internal error	The node failed to process the request

Library Integration

The idiomatic way to call Polkadot RPC is the Polkadot.js API (@polkadot/api), which connects over WebSocket and exposes the method as api.rpc.chain.getFinalizedHead.

polkadot-js.js

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

const provider = new WsProvider('wss://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/');
const api = await ApiPromise.create({ provider });

const result = await api.rpc.chain.getFinalizedHead();
console.log(result.toHuman());