How to connect gmail and facebook with an app?

Question

I am developing an application where I want to give the user choice to login with gmail or facebook. How can I connect user's gmail or user's facebook account with my application?

Answer 1

You chose
Firebase
It is better to you they help you to connect with Google and Facebook id

Answer 2

It is free cost available on Google

Answer 3

learn OAuth2.
https://developers.google.com/identity/protocols/OAuth2

not sure with facebook, never use it
https://developers.facebook.com/docs/facebook-login/