Android ADB Backup
Android backups (.ab) are backups made by Android Debug Bridge (ADB). They are the preferred way of backing up an unrooted stock android device. (Manufacturers and/or carriers may provide their own backup tools). They can be encrypted or unencrypted. They can be created via ADB backup and restored via ADB restore.
Flags
-all Backups all compatible apps
(package id) Backs up the stated package(s) if compatible.
-system backups system apps if -all or a system package Id is stated.
-nosystem does not back up system data.
-apk Backs up the .apk of the app(s)
-noapk does not back up apk files
-obb Backs up .obb (app extention) files
-shared Backs up all shared storage (/storage/emulated/0/), including SD cards and USB OTGs, so it is recommended to eject and disconnect any external storage unless you want to back up that.
-noshared does not back up shared storage.
Discontinuation
Android backups are being discontinued and fully replaced by Google Drive backups. Google drive backups cannot be downloaded, and there is a 25 MB per-app limit. You need a network sniffer to log upload traffic to capture these. The warning was there since Android 10 “Queen Cake”. In Android 12 “Snow Cone”, apps with Snow Cone’s API level with backup flag set to true and a Snow Cone device will back up to (dumb) Google Drive instead.