Fcm google

Using FCM, you can notify a client app that new email or other data is available to sync . You can send notification messages to drive user re-engagement and retention. For use cases such as instant messaging, a message can transfer a payload of up to 4000 bytes to a client app.

If you are using GCM with Intercom you will need to migrate to FCM.

Send messages to any device Firebase Cloud Messaging (FCM) provides a reliable and battery-efficient connection between your server and devices that allows you to deliver and receive messages and notifications on iOS, Android, and the web at no cost .

If the device comes back online FCM will notify the app that pending messages were deleted: When the device gets back online, FCM will call onDeletedMessages() on Android . When the app is opened, FCM will trigger FIRMessagingMessagesDeletedNotification on iOS to notify the app that pending messages were deleted.