What is the default android:sharedUserId set if android:sharedUserId was not set

Question

From the documentation:

The name of a Linux user ID that will be shared with other applications. By default, Android assigns each application its own unique user ID.

Say I have an app that does not specify android:sharedUserId in the AndroidManifest.xml file.

Is the default sharedUserId Android generates (see above documentation) set in the build (same for this app on all devices) or is a different sharedUserId being generated on each device the app is installed?

Answer 1

Android generate random unique ID for each application you installed on your device.

You can get this value by:

adb shell dumpsys package com.example.myapp | grep userId=

or in code with :

int uId = getPackageManager().getApplicationInfo("com.example.myapp",PackageManager.GET_META_DATA).uid;

But if you set android:sharedUserId with the same value for two or more apps, they will all share the same ID — provided that their certificate sets are identical.

Apps with the same user ID can access each other's data and, if desired, run in the same process.