Prevent Firebase Auth from creating multiple users with the same email from different providers

I have Email/Password & Google enabled as providers. I’m able to create a user with both providers and as a result I have two users with the same identifier (email) in Firebase. I need the identifier to be unique.

An answer in a rather old but same question on Stack Overflow says to:

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

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But this option doesn’t exist for me. The only thing I see under advanced is SMS Multi-factor Authentication. Is this maybe available on the Blaze plan (I have Spark) or was this removed over the years?

If there’s no setting, should this be set up with rules or do I need to do additional checks before calling either signInWithPopup or createUserWithEmailAndPassword?

>Solution :

That option is now on the authentication settings page (Authentication > Settings) and is called User account linking.