Deliver notifications that wake your app and update it in the background.
If your app’s server-based content changes infrequently or at irregular intervals, you can use background notifications to notify your app when new content becomes available. A background notification is a remote notification that doesn’t display an alert, play a sound, or badge your app’s icon. It wakes your app in the background and gives it time to initiate downloads from your server and update its content.
Enable the Remote Notifications Capability
To receive background notifications, you must add the remote notifications background mode to your app. In the Signing & Capability tab, add the Background Modes capability, then select the Remote notification checkbox (Figure 1).
For watchOS, add this capability to your WatchKit Extension.
Create a Background Notification
To send a background notification, create a remote notification with an
aps dictionary that includes only the
content-available key, as shown in Listing 1. You may include custom keys in the payload, but the
aps dictionary must not contain any keys that would trigger user interactions.
Additionally, the notification’s POST request should contain the
apns-push-type header field with a value of
background, and the
apns-priority field with a value of
5. The APNs server requires the
apns-push-type field when sending push notifications to Apple Watch, and recommends it for all platforms. For more information, see Create and Send a POST Request to APNs.
Receive Background Notifications
When a device receives a background notification, the system may hold and delay the delivery of the notification, which can have the following side effects:
When the system receives a new background notification, it discards the older notification and only holds the newest one.
If something force quits or kills the app, the system discards the held notification.
If the user launches the app, the system immediately delivers the held notification.
To deliver a background notification, the system wakes your app in the background. On iOS it then calls your app delegate’s
application(_: method. On watchOS, it calls your extension delegate’s
did method. Your app has 30 seconds to perform any tasks and call the provided completion handler. For more information, see Handling Notifications and Notification-Related Actions.