How to limit the number of authenticated users with Firebase

Question

I'm currently using Firebase for an online Android game in Kotlin (school project) to authenticate/register users. We're going to release our first version for testing, and I would like to set a limit of people that are able to sign up with Firebase (20 to be specific). Is this possible? Thank you in advance.

Answer 1

There is no way to limit the number of people that can sign in to Firebase Authentication. All authentication does is allowing you to say (and prove) that "I am Max", and there is no way to restrict in Firebase Authentication who can do that (beyond creating your own custom identity provider ).

But you can limit what these users can do in the rest of your app. If you're for example using the Firebase Realtime Database or Cloud Firestore, you'd restrict the users who can access the database with their respective server-side security rules ( Realtime Database , Cloud Firestore ).

If you have your own backend servers, you'll want to pass the ID token from the user to that server , and verify the token there to allow who can access what resources.