When you download your Facebook data, you get this photos/facedata.htm page:

MyReal RealName
Facial Recognition Data
Threshold 1 3.2382398572935
Threshold 2 3.0234235928592
Threshold 3 1.7239528352435
Example Count   120

What do these numbers mean?

  • google image search for faces by typing in numbers – fie Aug 22 '14 at 1:35
  • can your face really be accurately detected with 3 floating point numbers – fie Aug 22 '14 at 1:36
  • 3 floating point numbers can hold a lot of data. 14 digits is way too much for a single measure, even though the term "Threshold" tries to make us believe this. Maybe each number actually holds 7 measures or more. – nic Aug 22 '14 at 2:17
  • Newer versions of this file also include a new field "Raw Data," which has ~1000 characters that looks like data encoded with some Base64 variant. – Kaypro II May 3 '18 at 16:13

Example count is the number of pictures of you that Facebook has.

The Threshold values and Raw Data are produced by machine learning, and any picture of you should generate similar numbers. This data helps Facebook guess whether a picture shows your face or not.

Rather than storing individual measures such as "proportion of nose", machine learning store such values that have no easily understandable meaning to humans:

So what parts of the face are these [...] numbers measuring exactly? It turns out that we have no idea. It doesn’t really matter to us. All that we care is that the network generates nearly the same numbers when looking at two different pictures of the same person.

