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This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The ServiceWorkerGlobalScope.onsync event of the ServiceWorkerGlobalScope interface is fired whenever a SyncEvent event occurs. This is triggered when a call to SyncManager.register is made from a service worker client page. The attempt to sync is made either immediately if the network is available or as soon as the network becomes available. 


ServiceWorkerGlobalScope.onsync = function(SyncEvent) { ... }
self.addEventListener('sync', function(SyncEvent) { ... })


Specification Status Comment
Web Background Synchronization
The definition of 'onsync' in that specification.
Living Standard Adds the onsync event.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 49.0 ?[1] ? ? ?
Feature Android Android Webview Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support No support No support ? ? ? ? ? 49.0

[1] Service workers (and Push) have been disabled in the Firefox 45 Extended Support Release (ESR.)

Document Tags and Contributors

 Contributors to this page: chrisdavidmills, rolfedh, jpmedley
 Last updated by: chrisdavidmills,