Understanding Silent Push Notification Behavior and Limits on iOS

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

Frequency of Silent Push Notifications

There is no strictly defined frequency limit for triggering 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.

Generally, a device user might expect to receive approximately 1-2 silent notifications in total per hour across all apps that utilize this functionality, provided the device's conditions allow it. These conditions include 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 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 limit on the number of silent push notifications that can be sent to a device within a given timeframe. The delivery of these notifications is subject to the same dynamic factors mentioned 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.
• Respect user settings: Users can disable push notifications or background app updates at any time, which will prevent the 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. Additionally, if a user has not launched an app for an extended period, silent notifications may not be delivered.
• Avoid for critical timing: Silent push notifications are not a reliable method for implementing 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, while there are no hard-coded limits on the frequency or number of silent push notifications, their delivery is not guaranteed and depends on various dynamic factors managed by the iOS system. Designing your application with this understanding is essential for a robust and user-friendly experience.