How many time Anonymous users are created in Firebase

An anonymous user account is similar to any other user account in Firebase, except that there is no way to identify the user.

Anonymous users are not automatically removed.

Each time you call the API to create an anonymous user, a new account will be created. To re-use the existing account, you should listen for the auth state when the app starts and only create a new user account if the user isn't signed in yet.

If the same (anonymous) user signs in from multiple devices, they will get a separate account on each. If that is not what you want for your use-case, you should require one of the identified authentication methods (email/password, Facebook, Google, etc)/