How get the user id if the user isn't connected to your app?

Question

Is it possible to get the user id if the user isn't connected to your app?

Answer 1

If you have the users login name (i.e. email) you can do a query like this:

https://graph.facebook.com/search?q=USER_LOGIN&type=user&access_token=ANY_ACCESS_TOKEN

You can use any valid access token to run this request.

The resulting Data object contains user name and user id.

Answer 2

Facebook doesn't allow you that without permission!

https://graph.facebook.com/me