ServiceWorkerGlobalScope: sync event

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

Note: This feature is only available in Service Workers.

The sync event of the ServiceWorkerGlobalScope interface is fired when the page (or worker) that registered the event with the SyncManager is running and as soon as network connectivity is available.

This event is not cancelable and does not bubble.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

js
addEventListener("sync", (event) => {});

onsync = (event) => {};

Event type

A SyncEvent. Inherits from ExtendableEvent and Event.

Event ExtendableEvent SyncEvent

Event properties

Inherits properties from its ancestor, ExtendableEvent and Event.

SyncEvent.tag Read only

Returns the developer-defined identifier for this SyncEvent.

SyncEvent.lastChance Read only

Returns true if the user agent will not make further synchronization attempts after the current attempt.

Examples

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

js
self.addEventListener("sync", (event) => {
  if (event.tag === "sync-messages") {
    event.waitUntil(sendOutboxMessages());
  }
});

You can also set up the event handler using the onsync property:

js
self.onsync = (event) => {
  // ...
};

Specifications

Specification
Web Background Synchronization
# dom-serviceworkerglobalscope-onsync

Browser compatibility

BCD tables only load in the browser

See also