Is it possible to prevent duplicate emails from signing up?

I noticed that Auth0 allows duplicate emails to be signed up through different providers (ie, Google OAuth can sign in a gmail account, and then that same gmail can sign up through the email/password function).

I was wondering if there is any way I can prevent Auth0 from allowing this to happen when a user tries to sign up.

I know how to use the Account Linking Extension, but this method cannot prevent it completely, since it is up to the user to decide whether to merge accounts.

Is it possible to use Rules or Hooks to prevent duplicate emails from signing up?
If this is possible, please share a sample script.

Also, please let me know if there is another way.


Hi @nakatatsu711,

Welcome to the Auth0 Community!

I understand you’d like to prevent signups from users that have already created an account with the same email in a different connection/provider.

It doesn’t seem possible using a hook/pre registration action due to the fact that these don’t run for any connections that are database connection (they don’t run for social connections for example).

There are some strategies outlined in this thread:

It might be worth it to create a Feature Request for this as it seems like there is some demand.

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