How to save facebook user by changing app id?

Question

Facebook

There is an application on Facebook through which users enter the site.
When I log in to the site, I save the user_id that comes from facebook in order to further distinguish the user.
There was a need to change the application to Facebook, through which people pass authorization. I created a new application, changed IDs, but now, existing users who log in through this new application enter the site with a completely different user_id. That is, I cannot compare them with existing users. How to be?

Answer 1

This is possible using Business Manager + https://developers.facebook.com/docs/facebook-logi...

Answer 2

No, it's impossible