Notifications Delayed

Common reasons why App Push Notifications can be delayed or not shown quickly

Normally push notifications arrive quite quickly. The most common reason for notifications being delayed is the device has unstable or no internet connection and the notification did not arrive until the connection was made (TTL - defaults to 1 day).

When notifications are sent from iZooto, they go to Google (FCM), Apple (APNS), and other messaging servers. iZooto is responsible for sending these requests to these Push servers which then deliver them to your subscribers.

If the device receiving the push does not get it right away, it could be an issue with the FCM, APNS servers (rare) or the device had an unstable internet causing a delay (common).

Other issues can be as follows:

Delays for Notifications on Android Devices

  1. Some home and commercial WiFi routers will cause the device's connection to Google's FCM servers to be closed. The device later re-opens the connection and receives the delayed notifications. (Discussed here: https://groups.google.com/forum/#!topic/android-gcm/Y33c9ib54jY).

  2. Some custom versions of the Android OS have a "power-saving" setting that can cause notifications to be delayed or ignored. For instance, Sony Xperia devices have a Stamina Mode and other devices have similar modes discussed in our Notifications Not Shown on Device Guide.

  3. Some Android devices can enter a low power mode when their battery is low that may cause slight delays in receiving notifications. This is more common in Android 9 devices with Power Management Restrictions:

  1. Doze Mode can delay notifications even when sending with the highest priority. This depends on Android's App Standby Buckets and is subject to change.

  2. Remote images and icons, adding an image to your notification could cause the notification to be delayed as it has to wait for the full image to download first. Try omitting your image temporarily to rule this factor out.

Delays for Notifications on iOS Devices

  1. Some home and commercial WiFi routers will cause the device's connection to APNS servers to be closed. The device later re-opens the connection and receives the delayed notifications.

  2. Notifications might be delayed if "Restrict Background Data" is checked for the app. If WiFi-Optimizations is turned on in the advanced settings, or if the priority mode is enabled.

  3. "Low Power Mode" is enabled. If your Settings > Battery > Low Power Mode is enabled, this will reduce the rate at which notifications can be received or turn them off completely.

  4. Data only notifications, without a message body, are sent at a normal priority instead of high due to Apple's limitations. These can be delayed by a few minutes.

  5. Development builds of your app connect to Apple's Sandbox APN server which may be slower. We recommend testing with release modes such as with an ad-hoc or test-flight build so your app will use the Apple Production APN server to rule out any delays the Sandbox server could cause.

  6. Notification media attachments, adding an image to your notification could delay it up to 30 seconds as it downloads it. Try omitting the image temporarily to rule this factor out.

WhatsApp has a good list of instructions on troubleshooting delayed Android and iOS notifications here: https://www.whatsapp.com/faq/en/android/20887936.

Delays for notifications on Web

  1. Some home and commercial WiFi routers will cause the device's connection to VAPID servers to be closed. The device later re-opens the connection and receives the delayed notifications.

  2. Depending on the browser being used, there are a few factors that determine if notifications can be received when the browser is not running.


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