Broadcast Channel

Broadcast Channel

BroadcastChannel is a publish/subscribe bus for one origin: every tab, iframe and worker that opens a channel with the same name receives each message, except the sender. It needs no server and no port passing, and it is Baseline Widely available. A classic use is logging out every tab at once.

Page script opened in tabs B and C, then A (A posts after 500 ms)JavaScript

const channel = new BroadcastChannel('auth');
channel.onmessage = ({ data }) => console.log(`${location.hash} got`, JSON.stringify(data));
const logout = () => channel.postMessage({ type: 'logout', at: new Date().toISOString() });
if (location.hash === '#tab-A') setTimeout(logout, 500);

Output

#tab-C got {"type":"logout","at":"2026-09-15T16:43:13.362Z"}
#tab-B got {"type":"logout","at":"2026-09-15T16:43:13.362Z"}

Messages are structured clones, so functions cannot be sent. Call channel.close() when a component unmounts.

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