As Facebook users tighten their security and privacy settings, a lot more information is coming to light about just how much Facebook really knows about each user.
When you upload something as seemingly innocent as a selfie, however, no matter how closed your account is, you are giving Facebook a large amount of data about yourself.
Every selfie you have ever uploaded to the social network has given away where and when you took the photo. Facebook can also gather what type of phone you’re using (and not just the brand and model but right down to your unique device ID), your mobile services provider, any wifi networks nearby and mobile towers.
A selfie even tells Facebook how much battery you’ve got on your phone.
If your selfie is taken in public and it includes other people, Facebook can also cross-reference the faces, using facial recognition technology, to know information about everyone included in the picture.
Source: NZ Herald