What Happens with Push Notifications When a Device Is Offline?

Push notifications are a powerful tool for real-time communication with users. However, there are times when a user's device may be offline due to various reasons such as being out of network coverage, in airplane mode, or simply turned off. This article explains what happens with push notifications when a device is offline and the mechanisms in place to ensure delivery.

How Push Notifications Work

Before diving into what happens when a device is offline, it's important to understand how push notifications work. Push notifications are sent from an app server to a push notification service (such as Apple Push Notification Service (APNs) for iOS, Firebase Cloud Messaging (FCM) for Android, or Web Push for web applications). The push notification service then delivers the notification to the user's device.

Handling Offline Devices

When a device is offline, the push notification service cannot immediately deliver the notification. However, push notification services have mechanisms in place to handle such scenarios and ensure that notifications are delivered once the device comes back online.

Apple Push Notification Service (APNs)

APNs stores the push notifications for offline devices and attempts to deliver them once the device reconnects to the network. APNs retains the notifications for a limited period, typically up to a few days. If the device remains offline beyond this period, the notifications may be discarded.

Firebase Cloud Messaging (FCM)

FCM also stores push notifications for offline devices and delivers them when the device comes back online. FCM allows developers to set a time-to-live (TTL) value for each notification, which specifies how long the notification should be stored if the device is offline. The TTL can range from a few seconds to several weeks. If the TTL expires before the device comes online, the notification is discarded.

Web Push

Web Push notifications are handled similarly. The push service stores the notifications for offline devices and delivers them when the device reconnects. The retention period for Web Push notifications varies depending on the push service provider and the TTL value set by the developer.

Best Practices for Handling Offline Scenarios

To ensure that your push notifications are effectively delivered even when devices are offline, consider the following best practices:

Set Appropriate TTL Values

Set appropriate TTL values for your push notifications based on the urgency and relevance of the message. For time-sensitive notifications, use shorter TTL values, while for less urgent notifications, use longer TTL values to increase the chances of delivery.

Use Notification Priorities

Use notification priorities to indicate the importance of your messages. High-priority notifications are more likely to be delivered promptly once the device comes online, while low-priority notifications may be delayed or discarded if the device remains offline for an extended period.

Implement Fallback Mechanisms

Implement fallback mechanisms to ensure that important messages reach your users even if push notifications are not delivered. For example, you can send an email or an in-app message as a backup to ensure that the user receives the information.

Monitor Delivery Status

Monitor the delivery status of your push notifications to identify any issues with offline devices. Use the analytics and reporting features provided by push notification services to track the delivery and engagement rates of your notifications.

Conclusion

When a device is offline, push notifications are stored by the push notification service and delivered once the device reconnects to the network. By setting appropriate TTL values, using notification priorities, implementing fallback mechanisms, and monitoring delivery status, you can ensure that your push notifications are effectively delivered even when devices are offline.

Consider these best practices to enhance the reliability and effectiveness of your push notification strategy and provide a better experience for your users.