Is the user_id from the facebook api unique?

Question

When I have users register on my website I store their user_id, and use that all over the site as a reference to who they are. (actually havent done it just planning) I want to make sure this user id is unique the the user though and doesnt change?

Answer 1

Yes,the user_id in facebook is unique for each facebook user.

You can try by comparing the userids for multiple facebook user accounts.