Web Periodic Background Synchronization API

The Periodic Background Sync API allows web applications to alert their service worker to make any updates, at a periodic time interval. Uses may include fetching latest content whilst a device is connected to Wi-Fi, or allowing background updates to an application.

The minimum time interval is set when the API is invoked; however the user agent might also take into account other factors which affect when the service worker receives the event. For instance previous website engagement, or connection to a known network.

The PeriodicSyncManager interface is available through ServiceWorkerRegistration.periodicSync. A unique tag identifier is set to 'name' the sync event, which can then be listened for within the ServiceWorker script. Once the event is received you can then run any functionality available, such as updating caches or fetching new resources.

As this API relies on service workers, functionality provided by this API is only available in a secure context.

PeriodicSyncManager

Registers tasks to be run in a service worker at periodic intervals with network connectivity. These tasks are referred to as periodic background sync requests.

PeriodicSyncEvent

Represents a synchronization event, sent to the global scope of a ServiceWorker. It provides a way to run tasks in the service worker with network connectivity.

The following additions to the Service Worker API are specified in the Periodic Background Sync specification to provide an entry point for using Periodic Background Sync.

ServiceWorkerRegistration.periodicSync Read only

Returns a reference to the PeriodicSyncManager interface for registering tasks to run at specific intervals.

onperiodicsync

An event handler fired whenever a periodicsync event occurs. This happens at timed intervals, that are specified when registering a PeriodicSyncManager.

The following examples show how to use the interface.

The following asynchronous function registers a periodic background sync at a minimum interval of one day from a browsing context:

async function registerPeriodicNewsCheck() {
  const registration = await navigator.serviceWorker.ready;
  try {
    await registration.periodicSync.register("get-latest-news", {
      minInterval: 24 * 60 * 60 * 1000,
    });
  } catch {
    console.log("Periodic Sync could not be registered!");
  }
}

This code checks to see if a Periodic Background Sync task with a given tag is registered.

navigator.serviceWorker.ready.then((registration) => {
  registration.periodicSync.getTags().then((tags) => {
    if (tags.includes("get-latest-news")) skipDownloadingLatestNewsOnPageLoad();
  });
});

The following code removes a Periodic Background Sync task to stop articles syncing in the background.

navigator.serviceWorker.ready.then((registration) => {
  registration.periodicSync.unregister("get-latest-news");
});

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") {
    event.waitUntil(fetchAndCacheLatestNews());
  }
});

• An article on using Periodic Background Sync
• A Periodic Background Sync demo app