Firebase Allowing Multiple Accounts from Same Email Address

Question

Within the Firebase console I have specifically set it to only allow "One account per email address". This is found on the sign-in method tab under "advanced".

I have an account created using the Google login method that has an address like "[email protected]". If I then choose to sign-in via Facebook using an account that also uses "[email protected]", Firebase is allowing it with the exception that the email address in the Users entity is null.

The Firebase documentation states:

if you don't allow multiple accounts with the same email address, a user cannot create a new account that signs in using a Google Account with the email address [email protected] if there already is an account that signs in using the email address [email protected] and a password.

Does this only count if you are trying to create a Firebase login directly with a username/password vs creating an account from two providers like Facebook and Google? I would be under the impression that if it finds a duplicate email address it should reject the registration/login. I do realize the quote states "and a password" which makes me wonder.

Answer 1

Go to Firebase Console

In the Authentication -> SIGN-IN METHOD

Scroll Down to Advanced Section Click on CHANGE and then SAVE

Answer 2

Step 1 : Go to Firebase Console > Authentication > Sign in method. Check the option preventing multiple account creation with single email id.

Step 2 :The following documentation explains how to connect multiple providers to a single account using custom method.

https://firebase.google.com/docs/auth/web/account-linking