Image by Jim Cooke/GMG

Facebook is constantly watching you. Now, you can watch Facebook back. Gizmodo Media Group’s Special Projects Desk is releasing a tool for people who want to study the friend recommendations Facebook chooses to give them. It’s called the “People You May Know Inspector.” To use the tool:

  1. Download the app installer on a Mac computer. (This won’t work on a smartphone or non Mac.)
  2. Once you’ve downloaded the app installer, open it and copy the PYMK Inspector app to your Applications folder
  3. Go to your Applications folder and open the app. You should see it pop up in your task bar.
  4. Go to Inspector settings and enter your Facebook credentials. (For those who have two-factor turned on, you’ll need to enter your second factor the first time you run the app.)
  5. You can test that it is working correctly by clicking on ‘Run it now.’

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Why we made this:

Facebook’s “People You May Know” feature has consistently mystified and unnerved users in the decade that it has been in existence: A familiar face pops up in the box, but you have no mutual Facebook friends with the person. How did Facebook figure out who your second-grade teacher was? Why is your ex’s new girlfriend’s mom there? How does Facebook know who your gynecologist or psychiatrist is?

We’ve written a lot of stories about People You May Know—PYMK, as Facebook likes to call it—trying to figure out more about what’s inside the algorithmic black box. What is fascinating about the feature is how many ways Facebook theoretically could link people, given the huge amount of data it has: location information from their smartphones, Wi-Fi networks they’ve used, IP addresses they’ve signed in from, the contact books of millions, which accounts they’ve looked at on Facebook...

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The company says it mainly relies on uploaded contacts, mutual friends, and shared networks (like schools or jobs)—yet it also says that there are dozens and dozens of other, unspecified kinds of information it may use.

Even if Facebook has given you an intrusive (or harmful) recommendation—as when it exposes sex workers’ real names to clients or refers a doctor’s patients to each other—the company won’t show you the data it used to make the connection. (Sometimes Facebook itself seems confused about how exactly the feature works.)

Since Facebook won’t discuss the input it uses, the alternative is to study the output it produces: to track your friend suggestions and see how they change from day to day. By looking at recommendations or patterns of recommendations, it’s possible to find connections that Facebook’s public explanations won’t cover and to try to figure out how they happened.

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We made the PYMK Inspector app (download link) to enable Facebook users to do this. Once you download it to your computer and enter your Facebook credentials, it will check your “People You May Know” suggestions every 6 hours and save that information to your computer, so you can review who has appeared there, and when, and how often.

We designed this tool with your privacy in mind. Your Facebook password and any data gathered from Facebook are stored on your computer. Only you have access. We gather no data, though if you see something (or rather someone) interesting, we’d love to hear from you. We made it open source; here is a link to the source code for the tool. We also commissioned a security review from Trail of Bits.

We’ve been using the tool since the beginning of the summer. Testing it internally, we’ve already uncovered some strange things. It’s how one of us discovered Facebook was recommending an unknown relative. And we’ve documented the fact that some people don’t have any friend recommendations at all. The “People You May Know” module doesn’t appear for our editor Tom Scocca, not sprinkled throughout the site and not on the Friend Request page where it appears for everyone else.

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Though Tom doesn’t see the tool anymore, he still appears in it. He was recommended to us as a friend, just one time, in the middle of June. (We didn’t friend him. Sorry, Tom!) While we actually know Tom, he only appeared in PYMK that one time, whereas other people we don’t seem to know have appeared there day after day, for months at a time.

Now we’re inviting you to join us in the research. If you’re curious about how Facebook is tracking your own connections, please download the tool and start studying your own results. If you see something you can’t explain, or something Facebook shouldn’t know, tell us about it. With your help, maybe we can see a little more clearly into the black box.


Contact the Special Projects Desk

This post was produced by the Special Projects Desk of Gizmodo Media. Reach our team by phone, text, Signal, or WhatsApp at (917) 999-6143, email us at tips@gizmodomedia.com, or contact us securely using SecureDrop.

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