Understanding Silent Push Notification Behavior and Limits on iOS

This article clarifies the behavior and limitations of silent (background) push notifications on iOS devices.

Frequency of silent push notifications

There is no strictly defined, hard-coded frequency limit for silent push notifications on iOS. The operating system and the device's power management features dynamically determine whether and when to deliver these notifications to apps.

Apple's own guidance is that the system may throttle delivery if the total number becomes excessive, and that the number allowed depends on current conditions — but you should not try to send more than two or three background notifications per hour for your app. Delivery also depends on network connectivity, battery level and the user's Background App Refresh settings.

It is crucial to understand that the push notification system, both on the server and on the device, reserves the right to pass on or ignore silent notifications at its discretion, potentially after an unspecified delay.

Limits on the number of silent push notifications

Similarly, there is no specific, fixed cap on how many silent push notifications can be sent to a device within a given timeframe. Delivery is subject to the same dynamic factors described above.

Best practices

• Do not rely on guaranteed delivery: Apps should never be designed with the expectation that every silent push notification will be received. The Apple Push Notification service (APNs) is designed to inform the user or app about an event of interest, not as a guaranteed data delivery mechanism.
• Design for potential non-delivery: Applications should function correctly, even if with reduced functionality, when silent push notifications are not received.
• Stay within Apple's rate guidance: aim for no more than two or three background notifications per hour, and avoid bursts.
• Respect user settings: Users can disable push notifications or Background App Refresh at any time, which prevents delivery of silent notifications. Lack of network connectivity will also prevent delivery.
• Consider app state: An app that has been force-quit by the user will not be woken in the background by a push notification. If a user has not launched an app for an extended period, silent notifications may also not be delivered.
• Avoid for critical timing: Silent push notifications are not a reliable method for features that require strict timing and guaranteed execution.

<...> Silent push notifications is not a good way to implement some functionality that demands strict timing and certain execution.

~ Apple DTS Engineer

In conclusion: there are no hard-coded limits on the frequency or number of silent push notifications, but delivery is not guaranteed and depends on dynamic factors managed by iOS. Apple's stated ceiling is two to three per hour. See Pushing background updates to your app.