v148 · web api · shipped
Extended lifetime shared workers
A new extendedLifetime: true option on the SharedWorker constructor keeps the worker alive after all its clients have unloaded. This lets pages hand off in-flight async work — network requests, IndexedDB writes, analytics flushes — to a shared worker that outlives any individual page, without needing a Service Worker.
at a glance
| Constructor option | new SharedWorker(url, { extendedLifetime: true }) |
|---|---|
| Effect | Worker stays alive after the last client unloads; terminates when it becomes idle (no pending tasks, microtasks, or Web Locks) |
| Standard SharedWorker | Terminates as soon as the last client disconnects |
| Shipped in | Chrome 148 (desktop + Android + WebView) |
| Origin trial ran | Chrome 139 – 148 |
| ChromeStatus | 5138641357373440 — Extended lifetime shared workers |
| Blog post | Extended lifetime shared workers — Chrome for Developers |
why it exists
Pages frequently need to complete async work (save data, flush events, finish network requests) after the user navigates away. navigator.sendBeacon() covers fire-and-forget POST, but not complex multi-step flows. Service Workers can run after page unload but add complexity — a shared scope, update lifecycle, and push infrastructure. Extended lifetime shared workers fill the gap: a shared worker with extendedLifetime: true stays alive long enough to complete in-progress work, then terminates naturally once idle.
usage
// Page code: create (or connect to) an extended-lifetime worker
const worker = new SharedWorker('/workers/persistence.js', {
extendedLifetime: true
});
worker.port.start();
// Hand off work before unloading
window.addEventListener('pagehide', () => {
worker.port.postMessage({ type: 'flush', data: pendingEvents });
});// persistence.js — shared worker
self.onconnect = (e) => {
const port = e.ports[0];
port.onmessage = async ({ data }) => {
if (data.type === 'flush') {
// Worker stays alive to complete this even after the page unloads
await fetch('/api/events', {
method: 'POST',
body: JSON.stringify(data.data)
});
}
};
port.start();
};lifetime rules
| Condition | Result |
|---|---|
| All clients connected — normal operation | Worker runs normally |
| Last client disconnects — standard SharedWorker | Worker terminates immediately |
Last client disconnects — extendedLifetime: true | Worker stays alive until idle (no tasks, no pending locks) |
| Worker holds a Web Lock indefinitely | Worker will not terminate — this is a foot-gun to avoid |
| Extended workers cannot be mixed with standard workers | A standard and extended-lifetime worker with the same URL are treated as separate workers |