The Android Backup Service provides cloud storage for apps that implement Key/Value Backup. During a key/value backup operation, the app's backup data is passed to the device's backup transport. If the device is using the default Google backup transport, then the data is passed to the Android Backup Service for archival. For more information, see How backup works.
Note: Backup data from Auto Backup is not stored in Android Backup Service. Apps that support Auto Backup do not need to register for the Android Backup Service.
Registering your application with Android Backup Service does not guarantee that it will always back up data using this service from Google. If you support data backup in your application, then it will back up using whichever backup transport is enabled on the device.
For more information about how data backup works on Android and how to use it in your app, read the Data Backup guide.
In addition, users can disable data backup functionality through the Android system's privacy settings. When a user disables backup, Android Backup Service deletes all saved backup data. A user can re-enable backup on the device, but Android Backup Service will not restore any previously deleted data.