Flutter and Firebase Authentication: How to login anonymously only once per user/IP address

Solution 1:

In Documentation it has been stated as :

If no previous anonymous account on the platform (for your specific application) has been created, when signing in anonymously Firebase will create a new unique user which will be persisted across app restarts/page reloads. If the user signs-out and re authenticates anonymously again, they will be signed-in with the previously created account.

One PR has been created to improve the document on github as when you sign out from an anonymous account, that account's UID is lost and cannot be retrieved, for more information you can refer to the thread. You can also refer to the article and video which dives into Firebase auth on Flutter.