Show warning when user logs in with non-existing identifier


for our mobile app and webapp we are using Universal Login with a custom login page and passwordless login.

We would like to show our users who try to login with a non-existing identifier a warning that the account does not exist yet and he explicitly needs to register first.

Now, technically both login and registration pages go through the same passwordless login flow. (I also unchecked the option to “Disable Signup” in the Passwordless settings to allow that new users can go through the ‘registration’ process.)

How can we show the users a warning that their account is not yet registered immediately after they entered their identifier address during a ‘login’? While allowing login with a new email address when they go through ‘registration’?

I see different options:

  • Custom API request after user entered identifier to check if there is an account for it (not so nice)
  • Use two different tenants (one with “Disable Signup” checked, one without) (I don’t know if that is feasible)
  • Change behavior: Show the warning only after the user has entered the code (use a rule to check if the user logs in for the first time, as explained here How to tell if a user is logged in for the first time? - #2 by mathiasconradt)

Do you see any other way without changing the behavior?

What would be your recommendation if we want to distinguish between ‘login’ and ‘registration’ even though it’s all the same from Auth0 passwordless login perspective?