Modifying the code inside the universal login page will not affect the context in which that code will run. Since it’s the browser that needs to open the page in a popup window, you’ll want to look at your application in order to trigger that behavior.
You’ll need a way to open the popup from the browser using JavaScript, and then have a callback page that closes the popup again after authentication (this will be your redirect; this is needed so that the popup doesn’t redirect inside its own window and stay open).
This gist is quite old so I would not recommend copy-pasting its contents directly, but the concepts should be consistent: OmniAuth login in popup · GitHub
- To log in, open a popup window with JavaScript to your Auth0 universal login page
- Upon authentication, your callback redirect should point to a page that closes the popup
I’m not a Ruby expert by any means, but from my understanding, this behavior isn’t built into the omniauth library so you will need to implement it yourself at the application-level.