← Communication & Background
Background Sync
Probing…Background Sync is a web platform capability in the Communication & Background category. Defer work until connectivity returns. Supported in Chromium 49+; not available in Firefox and Safari. Requires a secure context (HTTPS or localhost).
Secure context
Permission background-sync: unknown
Try it
Loading demo…
Code
const reg = await navigator.serviceWorker.ready
await reg.sync.register('demo-sync-tag')
const tags = await reg.sync.getTags()
// In the service worker:
// self.addEventListener('sync', e => {
// if (e.tag === 'demo-sync-tag') e.waitUntil(replayQueue())
// })Browser support
Chromium
49
Firefox
No
Safari
No
Frequently asked questions
Which browsers support Background Sync?
Supported in Chromium 49+; not available in Firefox and Safari.
Does Background Sync require HTTPS?
Yes. Background Sync needs a secure context, so it only works over HTTPS (or on localhost during development).
What is Background Sync used for?
Defer work until connectivity returns.
Can I try Background Sync in my browser?
Yes. shwcs.net runs a live Background Sync demo that probes your current browser and lets you try the API. Everything runs locally — nothing is sent anywhere.