Social media companies like Facebook, Twitter and LinkedIn want their users to spend more time,or do more, on their services — a concept known as engagement, said Sean Munson, an assistant professor at the University of Washington who studies the intersection of technology and behavior.

Facebook officials say that the more time users spend at its site, the more likely there will be a robust exchange of diverse viewpoints and ideas shared online. Others fear that users will create their own echo chambers, and filter out coverage they do not agree with. “And that,” Mr. Munson said, “is when you get conspiracy theories.”

Ben Smith, editor in chief of BuzzFeed, a news and entertainment site, said his rule for writing and reporting in a fragmented age is simple: “no filler.” News organizations that still publish a print edition, he said, have slots — physical holes on paper or virtual ones on a home page — that result in the publication of stories that are not necessarily the most interesting or timely, but are required to fill the space. It was partly to discourage such slot-filling that BuzzFeed did not focus on its home page when it first started, he said.

Mr. Kim of SimpleReach says he advises established media companies that “it’s dangerous to start chasing social. You’ll end up like everyone else, and you’ll lose your differentiation.” The question that older publications that are not “digital natives” like BuzzFeed have to ask themselves, Mr. Kim said, is “Are you creating content for the way that content is consumed in this environment?”

Ms. Haik, the Washington Post digital editor, is leading a team, started this year, that aims to deliver different versions of The Post’s journalism to different people, based on information about how they have come to an article, which device they are on and even, if it is a phone, which way they are holding it.

“We’re asking if there’s a different kind of storytelling, not just an ideal presentation,” she said. For instance, she said, people reading The Post on a mobile phone during the day will probably want a different kind of reading experience than those who are on a Wi-Fi connection at home in the evening.

The Post is putting time and energy into such efforts, Ms. Haik said, because it is “ultimately about sustaining our business or growing our audience.” More than half of its mobile readers, she said, are so-called millennials who consume news digitally and largely through social media sites like Facebook. Some publications have found a niche in taking the opposite approach. The Browser is edited by Robert Cottrell, a former journalist at The Financial Times and The Economist. Mr. Cottrell skims about 1,000 articles a day, he said, and then publishes five or six that he finds interesting for about 7,000 subscribers who pay $20 a year. A recent selection included the life of an early-20th-century American bricklayer and a study of great Eastern philosophers.