Facebook says it's changing its news feed, again. It says posts from friends and family will now come first, prioritized over posts from publishers and celebrities.

It's potentially worrisome news for media companies, whose traffic is heavily boosted by Facebook-driven clicks. But it's also only a small, vague peek into the black box that is Facebook's algorithm, which determines what version of the world is presented to the 1.65 billion people using the social network.

What Facebook released on Wednesday was a sort of guide to its " News Feed Values" ranking that determines the weight and priority of each post in your feed:

  1. "Friends and family come first."
  2. "Your feed should inform."
  3. "Your feed should entertain."

Next come sweeping approaches, such as Facebook is "a platform for all ideas" (a nod to the recent controversy over whether conservative-leaning stories get equal placement in the "Trending Topics" feature) and "authentic communication" (as in, "genuine" stories take precedence over "misleading, sensational and spammy" stories).

We still don't know how exactly Facebook's algorithm works and to what extent humans of Facebook have a hand on its tiller. As Recode says, this week's disclosure is, in a way, an acknowledgement of those concerns:

"Human beings don't cherry pick individual stories for your News Feed, but human beings do write the algorithms that determine what you see, explained Facebook VP Adam Mosseri, who oversees the News Feed product teams." 'I don't want us to talk about the algorithm as this third party,' Mosseri said. 'I want to really own the responsibility as a team and want people to understand there's a team [of Facebook employees] behind the experience.' "

This week's news is also part of an ongoing effort by Facebook to defend itself as a neutral party both politically and as a business model, which has been increasingly compared to that of a traditional media company.

The shake-up in news feed prioritization is particularly alarming to digital publishers, who have been looking to Facebook and other social media as a new venue for readership. The company's latest push has been for live broadcasts: Facebook pays leading news organizations, including NPR, to produce live video streams that run on its site.

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