META Meta Platforms Inc

Facebook Inc. shed new light on how it determines what its 1.65 billion users see each time they sign on, in its latest effort to demystify its inner workings.

The social network also said it would prioritize posts from friends and family in users' news feed over content from publishers and public figures, in hopes of persuading users to spend more time on the site.

The news feed changes could mean some publishers will see readership on Facebook decline "a small amount but a noticeable amount," said Adam Mosseri, the product manager who runs Facebook's news feed. "Some publishers may go up, some publishers may go down, some publishers may go down more."

The broader explanation about how the news feed works was outlined in a two-page document the company posted on its website. Its release comes amid growing scrutiny of Facebook, after a report last month that contractors suppressed conservative viewpoints from its trending topics feature. Facebook denied bias, but revealed that humans were involved in the selection of headlines to a greater extent than it previously disclosed.

The controversy also exposed broader confusion among users about what appears in their news feeds. Facebook relies largely on an algorithm, or computer program, that combs through roughly 100,000 signals and creates a "relevancy score" for each post for a specific user. No two users have the same news feed.

On Wednesday, Facebook made clearer than it has in the past that people also are involved in selecting and prioritizing items in the news feed.

"It's important for people to understand that there's a group of people who work on news feed, not just sort of like a third party agent that acts autonomously," Mr. Mosseri said.

He said Facebook wants to show users posts that those users want to see. "That is an opinion. That isn't neutral. That's not a political bias, but that is a bias and that is reflected in our decisions and therefore it is reflected in our ranking order," Mr. Mosseri said.

Facebook tweaks the algorithm often—roughly once a month over the last 2 ½ years. Many of the changes are aimed at making the feed less promotional and repetitive. Facebook generally discloses in broad terms when and how it has altered the formula.

Each change is tested in a small group of Facebook users. There are 200 people on Facebook's news feed team, led by Mr. Mosseri.

The latest tweak came after Facebook found that users felt posts from friends were being "drowned out" by publishers, Mr. Mosseri said. Facebook has become an important source of news for many users, who spend an average of 50 minutes a day on the social network, according to the company. As a result, publishers often post hundreds of items a day. Friends, by contrast, post just a few times a week, Mr. Mosseri said.

"The thing that we're worried about is people connecting to their friends less than they want because" publishers post so often, he said.

Posts from personal connections now trump those from public figures and publishers, Facebook said. It also said it would favor what it described as "authentic" posts, rather than spam or misleading articles, colloquially known as clickbait. "People don't like seeing clickbait, they complain about it, they report it. We get bug reports," Mr. Mosseri said.

Posts widely shared by Facebook users will be less affected. Once a user shares an article, video or other content, Facebook considers it "friend content," Mr. Mosseri said. That means it will appear higher in a user's news feed.

Write to Deepa Seetharaman at Deepa.Seetharaman@wsj.com

(END) Dow Jones Newswires

June 29, 2016 10:25 ET (14:25 GMT)

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