Article

Pushing Background Updates to Your App

Deliver notifications that wake your app and update it in the background.

Overview

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).

Figure 1

Enabling the remote notifications background mode

Enabling the remote notification background mode in your project’s Capabilities tab.Enabling the remote notifications background mode

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.

Listing 1

Sample payload for a background notification

{
   "aps" : {
      "content-available" : 1
   },
   "acme1" : "bar",
   "acme2" : 42
}

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(_:didReceiveRemoteNotification:fetchCompletionHandler:) method. On watchOS, it calls your extension delegate’s didReceiveRemoteNotification(_:fetchCompletionHandler:) 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.

See Also

Server Tasks

Generating a Remote Notification

Send notifications to the user’s device with a JSON payload.

Sending Notification Requests to APNs

Transmit your remote notification payload and device token information to APNs.

Handling Notification Responses from APNs

Respond to the status codes returned by the APNs servers.