How Facebook Decides What's Trending

Update - May 10, 2016: This story was based on a conversation we had in August with Facebook about how its trending feature works. A Gizmodo story published in May reports that human editors have suppressed certain conservative news stories and publications. Facebook denied that in a statement Monday.

"There are rigorous guidelines in place for the review team to ensure consistency and neutrality," a spokesperson said. "These guidelines do not permit the suppression of political perspectives. Nor do they permit the prioritization of one viewpoint over another or one news outlet over another. These guidelines do not prohibit any news outlet from appearing in Trending Topics."

Gizmodo also reported that editors were "instructed to artificially ‘inject' selected stories into the trending news module.’ We were told that humans do not choose trending topics, and Facebook has not responded to our questions asking for clarification.

This could mean a number of things: Facebook’s guidelines have changed since this story was published; Gizmodo’s story is inaccurate; the human editors were acting outside management's guideline; or Facebook gave us inaccurate information. We will update if we get an answer.

Update II - May 10, 2016: Facebook issued a lengthy statement Monday night further addressing the Gizmodo report. In it, Facebook claims: "We do not insert stories artificially into trending topics, and do not instruct our reviewers to do so."

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People get their news from Facebook — a lot of people, it turns out.

What that news is, though, depends on whom you follow and what pages you like. It also depends on what the broader Facebook community chooses to talk about. A combination of these elements determines what you see on the right side of your News Feed every time you log in.

Facebook

But how exactly does Facebook decide what to put in the Trending queue? And why is it that trends sometimes show up hours if not days after they may be trending somewhere else (cough Twitter cough)?

Facebook shows you things in your Trending line-up the same way it shows you things in your News Feed: Algorithms. It takes into account a few personal things, like where you live and what Pages you follow. But primarily it looks for two broader signals: Topics that are being mentioned a lot and topics that receive a dramatic spike in mentions.

You can’t have one without the other. For example, Kim Kardashian is mentioned often on Facebook, so the total volume of mentions is always high and isn’t a good indicator of whether or not she’s part of a trending topic. Instead, Facebook looks for a spike in mentions relative to the normal chatter around Kim (and probably other celebrities, too). Things that trend aren’t just the most highly mentioned people or topics. They have to be tied to some kind of relevant event.

This is probably a good time to mention that what is important on Facebook (e.g. Zac Efron and Jimmy Fallon smashing eggs onto their heads) may be slightly different from what’s important to the New York Times.

THIS JUST IN — BREAKING NEWS FROM FACEBOOK pic.twitter.com/IgEGfSPRrX

— EditingAndLayout (@EditingNLayout) August 13, 2015

One key for those of you who use Twitter to get your news — and there are a lot of you, too — is that "trending" on Facebook is different from "breaking." Twitter specializes in breaking news, an area where Facebook has struggled. Facebook launched its own Newswire service in early 2014 which now has just over 100,000 followers, a very small number compared to the site’s 1.5 billion users. (To be fair, the newswire is available to everyone but intended for journalists.) It has, more recently, been working on a breaking news app that sounds like a more direct competitor to Twitter, according to Business Insider.

That trending/breaking difference is an important distinction, especially for advertisers running a campaign to coincide with a specific trend. Not all trending stories on Facebook are happening right now. It’s just that people are talking about them right now, and that’s why the Super Bowl may be trending for days after the game is already over. For marketers trying to "join the conversation" on Facebook, understanding why and when something is trending is important, and still somewhat of a black box.

Advertisers want to reach as many people as possible, but they also want efficiency, which means reaching those people in as short a window as possible. Depending on the ad campaign, a long tail of mentions isn’t necessarily as effective as a quick spike, which is why TV is still very attractive to advertisers: TV has the power to gather lots of people at the same time.

Once a topic is identified as trending, it’s approved by an actual human being, who also writes a short description for the story. These people don’t get to pick what Facebook adds to the trending section. That’s done automatically by the algorithm. They just get to pick the headline.

It’s an imperfect system, sure — you’re bound to see things you don’t care about, and things that seem downright silly. (One perk of the system is that you can hide trends you don’t like.) But the next time you see "Deez Nuts" in your Trending topics, at least you’ll know to blame everyone else on Facebook.

This article originally appeared on Recode.net.

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