A background push notification is a silent, remote notification that helps keep your app’s data up to date. Unlike regular push notifications, background push notifications do not show app icon badges, trigger a sound, or display a message when received by your app. The system wakes the app in the background for a short time to silently initiate downloads, update content, or perform other actions.
If your app’s server-based content changes at irregular intervals, background notifications can be used to alert your app and refresh content. Background notifications are treated as a low priority; their delivery isn’t guaranteed by the system. If the total number of background notifications becomes excessive, the system may defer their delivery in a process known as throttling. If your background push notifications are throttled, they might be delayed until the next time another notification is received.
When a background notification is received by a device, the system may hold and delay the delivery of the notification, which can have the following side effects:
- If the system receives a new background notification, it only keeps the newest one and gets rid of older notifications.
- If something force quits or kills the app, the system discards held notifications.
- If the user launches the app, the system immediately delivers the held notification.