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chain_subscribeFinalizedHeads

Description#

Subscribe to real‑time chain updates over WebSocket. Use to stream new or finalized heads or runtime version changes into your app.

Emits new finalized block headers. Requires WebSocket.

JavaScript (polkadot.js)#

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

const api = await ApiPromise.create({ provider: new WsProvider(S.wsBase) });
const unsub = await api.rpc.chain.subscribeFinalizedHeads((header) => {
  console.log('finalized #', header.number.toString());
});
// Later: await unsub();