From the comments it sounds like the real answer is cookies: https://www.reddit.com/r/privacy/comments/am1hi0/a_created_a_fake_account_and_facebook_still/efj6tz

From the comments it sounds like the real answer is cookies: https://www.reddit.com/r/privacy/comments/am1hi0/a_created_a_fake_account_and_facebook_still/efj6tz4/?context=3 https://www.reddit.com/r/privacy/comments/am1hi0/a_created_a...