SuperTokens is an open source authentication solution offering features like: Different types of login: Email / password, Passwordless (OTP or Magic link based).

SuperTokens.com

Frontend seems to send traffic to supertokens.io/dev/oauth/redirect-to-provider, why?

Cause you must be using our dev OAuth credentials

If you switch them to your own OAuth client id / secret, that won’t happen

Oh. How did you create a Google OAuth that works for all domains? That's great, I want to do the same.

You need a proxy domain in the middle similar to what we have