chain_subscribeFinalizedHeads

Description

Creates a subscription that pushes every newly finalized block header. Useful for indexers that only act on finalized data.

Parameters

This method does not require parameters.

Notification Payload

Field	Type	Description
number	string	Block number in hex
hash	string	Block hash
parentHash	string	Parent block hash
stateRoot	string	State root
digest	object	Consensus digest items

JavaScript Example

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

const provider = new WsProvider('wss://api-astar.n.dwellir.com/YOUR_API_KEY');
const api = await ApiPromise.create({ provider });

api.rpc.chain.subscribeFinalizedHeads((header) => {
  console.log(`Finalized block #${header.number.toString()} (${header.hash.toHex()})`);
});

WebSocket JSON-RPC Example

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "chain_subscribeFinalizedHeads",
  "params": []
}

A notification payload will arrive on the same connection with method: "chain_finalizedHead" and the header data in params.result.