Can the Firebase user id change?

Question

Can the Firebase user id change? What I talk about is this, FirebaseAuth.getInstance().getCurrentUser().getUid() If user delete his account like it is described

Answer 1

As said by @user663031, the answer "no" is correct.

To add on to @user663031's answer, I'm working on a project, but I have to switch between the live database and the test database. I created a user (in firebase authentication) in both test & live environment with the same email address & password, however the id's are different.

In order to achieve proper tests in both environments, I had to change id stored in real time database so that it matches the "unchangeable id" in authentication.