Facebook’s ‘People You May Know’ feature can be really creepy. How does it work?

Company Correction — April 1, 2018: When reporting this story on how Facebook recommends connections for its “People You May Know” feature, we asked Facebook if it collected text and call data from users. The company said no.

In March 2018, we learned that Facebook does indeed collect text and call data from some Android users through its Messenger app. We went back to Facebook to ask why we were told otherwise. A company spokesperson said Facebook’s answer at the time was specific to the Facebook app, not the Messenger app. It wasn’t clear to us that this answer was specific to the core Facebook app, and the company did not offer up info at the time that Messenger was collecting this data. We assumed their denial about collecting this data was company-wide.

Here’s a statement from a Facebook spokesperson.

“Recode contacted us about a story on People You May Know and what information Facebook used to make friend suggestions. Among other examples, we were asked whether Facebook used information about who you call and text to make friend suggestions. We said that we didn’t, and we also explained that the Facebook for Android app didn’t collect this information. At the time, people could choose to share this information with Messenger, but it was not used for People You May Know.”

———

Facebook has a pretty clear and straightforward company mission: Connect everybody in the world.

One of the ways it carries out that mission is by recommending new friends for you every time you open the app or website — essentially, the company identifies other people on Facebook that it thinks you already know, and nudges you to connect with them inside Facebook’s walls.

The problem with this feature is that it can be really creepy.

Facebook previously employed user locations to recommend friends, but says it has stopped doing that; Fusion recently wrote about a psychiatrist who claims her mental health patients were being prompted to connect with one another on the service. Not good.

When my colleague Jason Del Rey and I recently experienced a number of oddly timed recommendations, we started to get curious ourselves. How does Facebook generate these eerily coincidental recommendations?

In one instance, Jason saw an acquaintance pass by him on the street, but didn’t stop to talk to him. A few hours later, Jason appeared as a recommended friend on the acquaintance’s Facebook account. In another, Jason met with a company spokesperson he hadn’t previously met. Within a few hours, that person appeared at the top of Jason’s recommendations.

I experienced other odd moments, like seeing an acquaintance I’ve known for years atop the list while waiting in the lobby of his office. In another, I looked up a new acquaintance on LinkedIn before a meeting and, hours later, Facebook recommended we connect.

In all of these instances, it sure seemed like Facebook was using some kind of tracking — either location or web tracking — to inform these recommendations. So we asked Facebook about it.

Facebook insists that the shared location in the cases above were coincidences. Instead, the most likely explanation for most of these scenarios was that the other person may have been looking at our profile or may have recently added us to their phone’s contact list.

These recommendations are, after all, a two-way street. Facebook can be a good directory for looking up basic information about others you plan to meet or call, or those you just caught up with on a street corner. And it’s possible the people recommended to us were triggering Facebook’s algorithm based on their online activity.

Still, the feature can be unsettling. So we asked Facebook a number of questions about how these recommendations come together. Here are the company’s answers, courtesy of a spokesperson and summarized by Recode.

Does Facebook use your location for friend recommendations?

No. The company claims that while it previously used location info like “whether two people live in the same city as a way to rank friend suggestions,” it’s no longer using location data at all for this product.

Does Facebook use my phone contacts to make friend recommendations?

Yes. If you share your phone contacts with Facebook or Facebook Messenger, the company will use that info to recommend your contacts as “Friends you may know.” Timing is a factor here. That means that you may be more likely to see a friend recommendation from someone you recently added to your phone, versus a contact you’ve had for years.

Do both parties need to be saved into each other’s phones?

No. If someone has added your number to their contact list, you might see them in your suggested friends list even if you’ve never added their number to your own contact list. It only takes one user to trigger a recommendation.

Can Facebook see who you call or who you text?

No. Facebook says it does not look at who you call or text. It technically could do so on an Android device because Google allows that information to be shared, but Facebook says it does not utilize this capability.

Can Facebook see who you email?

No. Facebook claims that it cannot see your emails, but there’s a caveat: Facebook says that “some common email programs automatically save contact information to your phone’s contact book when you email someone.” That includes Gmail. Remember that Facebook can see your contact book if you share it, so sending someone an email could mean they’re saved in your phone, and thus used in friend suggestions.

What about web activity? Can Facebook see who I look at on LinkedIn, for example?

Facebook does use web cookies to show you ads. But no, it doesn’t use this web activity to recommend new friends. “We do not use cookies from third-party sites to generate or rank People You May Know suggestions,” Facebook says.

This article originally appeared on Recode.net.