Facebook has overhauled how it ranks the posts, videos and photos that appear in its users’ News Feeds, introducing major changes on Thursday designed to put what friends and family have to say first.

In short, you’ll see more posts from friends that have spurred lively debates in the comments. And you’ll see fewer cooking videos from brands and publications. Prioritizing what your friends and family share is part of an effort by Facebook to help people spend time on the site in what it thinks is a more meaningful way.

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Facebook is making the changes by tinkering under the hood, reconfiguring its algorithms that guess what you may be most interested in. Here’s what it means for you.

Facebook is not being coy about this: Those third-party organizations that took over large swaths of your News Feed years ago — sites that post funny pictures and memes, sell you clothing, or deliver articles about the world — will have the visibility of their posts scaled back under the new arrangement.

In a post on the company’s blog Thursday, the head of its News Feed team, Adam Mosseri, wrote that showing more posts from friends and family “means we’ll show less public content, including videos and other posts from publishers or businesses.”

For many people, that news will come as a relief. In December, Facebook itself acknowledged that passive consumption of information — surfing shopping websites or reading news articles like this one — is often bad for your mood. (Sorry!)

It gestured toward a 2015 paper in the Journal of Experimental Psychology that showed that passive usage of the website, even for just 10 minutes a day, had a negative effect on students’ sense of well-being.

Those who still want to see posts from their favorite brands and trusted, wonderful publishers, one of whose articles you may be reading at this very moment, will be able to. The options under the News Feed tab on Facebook will allow users to prioritize the pages (and friends) whose posts they are most interested in.

And Mr. Mosseri explained that other posts that your Facebook connections find engaging will also rise to the top. Conversations stemming from live videos, celebrities’ posts, private groups and other highly interactive post types will be among those highlighted on the new News Feed.

Without that kind of explicit direction, though, Facebook’s top priority will remain posts from your friends and family.

“To do this, we will predict which posts you might want to interact with your friends about, and show these posts higher in feed,” Mr. Mosseri wrote. A video attached to his postsaid that indicators the algorithm takes into account are likes, comments and shares.

Facebook will remain customizable, with the options that allow you to limit your exposure to certain people — even if those people are your pesky siblings or that one over-the-top uncle. One option is to quietly “snooze” a Facebook friend, which will cause their posts to disappear from your feed for 30 days.

Facebook says that it has long been its policy that “friends and family come first,” language that appeared in the site’s “News Feed Values,” which were posted in 2016.

Facebook expects you’ll spend less time on the site.

Implicit in the changes that Facebook introduced this week is that for many users, the News Feed had become mindless scrolling, moving from one autoplaying video to the next, without offering people much of substance. It was serving up junk food.

In an interview with The New York Times, Mark Zuckerberg said that it was the company’s expectation that many users would be gravitating to other sites to get their viral fix. But with more than two billion monthly users, Facebook has gained a foothold that allows it to play a longer game. And Mr. Zuckerberg said that if people begin to feel better while on the site, that Facebook’s business, and its users, will benefit.

“I expect the time people spend on Facebook and some measures of engagement will go down,” he said in his post about the changes. “But I also expect the time you do spend on Facebook will be more valuable.”