Introducing the Background Sync API

Background synchronization

Background synchronization is a powerful feature that allows developers to schedule network requests to be retried automatically in the background, even if the users close the browser or navigate away from the page. This can be particularly useful when a web application needs to perform critical network operations, such as sending messages or uploading files, but network connectivity is unreliable or intermittent.

For example, a messaging application can use background synchronization to queue up messages to be sent when network connectivity is available again. This will ensure that users can send and receive messages reliably, even if they are in an area with poor network coverage.

The Background Sync API

The Background Sync API is implemented as part of the service worker API, which provides a way for web developers to run scripts in the background, independent of the main page. This API is particularly useful for applications that need to perform operations that require a network connection but can be deferred until the user has an internet connection, such as uploading images, sending messages, or syncing data.

When a service worker is registered for a web application, it can intercept network requests made by the application and respond to them in a customized way. This enables the implementing of powerful offline capabilities, such as caching and background synchronization.

The working of the Background Sync API

To use the Background Sync API, the service worker needs to register a sync event—a special event triggered when the browser detects that the device has network connectivity again. When the sync event is triggered, the service worker can perform necessary network operations, such as sending queued messages or uploading files that previously failed due to network errors.

In other words, we store network requests if the users are offline. Then, once connectivity is reestablished, we automatically send those stored network requests in the background, even if the app is closed.

This allows the web application to maintain a seamless user experience without relying on network availability.