android - What is the difference between changing package name vs applicationId

Question

What is the difference between changing package name vs applicationId to the final apk.

I know it is different for aspect of keeping source code, but lets say I got some app with package name a.b.c.d. What will be the difference in the builded apk file

1. if I rename the a.b.c.d into q.w.e.r and then build the apk file

vs

2. change the applicationId into gradle with q.w.e.r

Answer 1

The package name is just to organize your code.

The applicationId, on the other hand, is used to identify your app in the Play Store. You will change this only if you plan to generate another app based on same code.

From docs (https://developer.android.com/studio/build/application-id.html):

When you create a new project in Android Studio, the applicationId exactly matches the Java-style package name you chose during setup. However, the application ID and package name are independent of each other beyond this point. You can change your code's package name (your code namespace) and it will not affect the application ID, and vice versa (though, again, you should not change your application ID once you publish your app). However, changing the package name has other consequences you should be aware of, so see the section about modifying the package name.