Oauth2 flow without redirect_uri

Question

I am creating an Android/iOS app which communicates with a Node.js server and would like to identify them securely on my server using Google (and/or Facebook) and OAuth2. I\

Answer 1

The redirect_uri can be a URL with a custom URL scheme for which the client registered a handler. This is described here: What's a redirect URI? how does it apply to iOS app for OAuth2.0?. It is not so much about "redirecting" it is about a callback endpoint to your app.