adb backup dosen't work even with allowBackup=true I noticed that for some system apps (for example chrome, which is preinstalled by default on my device) I can't do adb backup . Doing so results in the 47 bytes dummy .ab file. I checked in manifest they have allowBackup=&quot;true&quot;.

Eg for chrome this is:
allowBackup=&quot;true&quot; backupAgent=&quot;org.chromium.chrome.browser.ChromeBackupAgent&quot; extractNativeLibs=&quot;false&quot; fullBackupOnly=&quot;false&quot;.

Why this is happening? How can I backup such apps' data without root?
PS: Helium backup doesn't show system apps.
I found the reason in logcat while performing an backup:
BackupManagerService: Package com.android.chrome is key-value.

By default for abd backup keyvalue backups are disabled:
&quot;/system/bin/bu&quot; (the command that is called on-device by adb backup) help text: 

 -keyvalue|-nokeyvalue: include apps that perform key/value backups.
     (default -nokeyvalue)

Therefore you need to include the -keyvalue option to create a chrome backup:
adb backup -keyvalue -f chrome.ab com.android.chrome

This creates a backup file that contains only the chrome settings (no cache files, cookies, local data ...)