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The PeriodicSyncEvent interface of the Web Periodic Background Synchronization API provides a way to run tasks in the service worker with network connectivity.

An instance of this event is passed to the ServiceWorkerGlobalScope.onperiodicsync handler. This happens periodically, at an interval greater than or equal to that set in the PeriodicSyncManager.register() method. Other implementation-specific factors such as the user's engagement with the site decide the actual interval.


Creates a new PeriodicSyncEvent object. This constructor is not typically used. The browser creates these objects itself and provides them to ServiceWorkerGlobalScope.onperiodicsync callback.


PeriodicSyncEvent.tag Read only
Returns the developer-defined identifier for this PeriodicSyncEvent. Multiple tags can be used by the web app to run different periodic tasks at different frequencies.


Inherits methods from its parent ExtendableEvent.


The following example shows how to respond to a periodic sync event in the service worker.

self.addEventListener('periodicsync', event => {
  if (event.tag == 'get-latest-news') {

fetchAndCacheLatestNews is a developer defined function.


Specification Status Comment
Web Periodic Background Synchronization
The definition of 'PeriodicSyncEvent' in that specification.
Working Draft Initial definition.

Browser compatibility

BCD tables only load in the browser

See also