SharedWorker on Android

concepts

1. Cross-Tab Counter

   Open this page in two tabs. Both connect to the same SharedWorker. Clicking +1 in one tab updates the count in the other instantly — that's the worker's shared state in action, mobile included.

2. Shared Clock

   One worker, one timer, many tabs. The motivating use case from whatwg/html #11205: every tab sees the same upstream "feed" tick through one shared connection instead of N parallel ones. Open in multiple tabs and watch them sync.

3. Collaborative Notes

   Three simulated tabs share a single SharedWorker message bus. Type in any tab and the note syncs instantly to all others — the worker is the single source of truth, the way it now works on Android too.

4. Shared State Board

   A full multi-tab dashboard via a SharedWorker: synchronized online-users list, broadcast counter, shared clipboard, and live chat — all persisted in worker memory. A connection log shows port connect/disconnect events, with a BroadcastChannel fallback for browsers without SharedWorker support.

5. Persistence Across Reload

   A counter that lives inside a SharedWorker — not in localStorage. Click "Simulate reload" to disconnect and reconnect to the same worker. The counter survives page reloads as long as at least one client is connected, showing the exact use case that's now available on Android Chrome 148+.

why it shipped

SharedWorker was disabled on Android because the process lifecycle was unpredictable; a worker could be killed without notifying its connected pages. A 2025 GitHub discussion (whatwg/html #11205) showed the problem was less severe than feared, and the long-standing demand for resource sharing across mobile tabs — single WebSocket, shared SSE, persistent WASM-SQLite — outweighed the residual risk. Re-enabling closes a feature gap with iOS Safari and Firefox Android.

references

• ChromeStatus entry
• HTML spec: SharedWorker
• whatwg/html #11205 — the discussion that reopened it
• MDN: SharedWorker