There are multiple different backup techniques:

• USB
• Google Cloud
• 3rd Party

Is app data stored in a backup?

• Check the androidmanifest.xml for allowBackup .
• From API 23+ this defaults to true if omitted
• When true it means the app can be backed up
• If the device is encrypted , the backup will be encrypted too

AutoBackup

• Autobackup is also configured in the àndroidmanifest.xml
• Apps that target API 23+ automatically participate in autobackup
• Autobackup uploads app data to the users google drive account
• 25MB per user of the app
• Includes, shared prefs, internal storage, databases, external storage
• android:allowBackup must be false to disable.

Backup Rules

• Rules can be configured to only backup parts of an application as part of autobackup
• defined in androidmanifest.xml
• XML file will reside in res/xml directory

Taking a backup

adb backup -apk -nosystem com.your.app

dd if=mybackup.ab bs=24 skip=1 | openssl zlib -d > mybackup.tar

tar xvf mybackup.tar 

Restoring a backup

adb restore mybackup.ab