X Slows Down Access to Some Rival Sites

X, the social media service formerly known as Twitter, slowed down access from its platform to rival sites such as Substack and Facebook, but on Tuesday began reversing an effort to restrict its users from quickly viewing news sites, according to a New York Times analysis.

The slowness, known in tech parlance as “throttling,” initially affected rival social networks including Facebook, Bluesky and Instagram, as well as the newsletter site Substack and news outlets including Reuters and The New York Times, according to The Times’s analysis. The delay to load links from X was relatively minor — about 4.5 seconds — but still noticeable, according to the analysis. Several of the services that were throttled have faced the ire of X’s owner, Elon Musk.

By Tuesday afternoon, the delay to reaching the news sites appeared to have lifted, according to The Times’s analysis.

X did not comment on the throttling, which was first noticed by users. The Washington Post earlier reported on X’s move to delay links to competing services.

Mr. Musk has previously slowed down access to other websites from X. Last year, he briefly blocked links to Mastodon, a competing service. In April, he also temporarily prevented users from sharing Substack links on X after the company said it planned to launch a Twitter competitor.

In recent weeks, Mr. Musk has sparred online with Mark Zuckerberg, the founder of Facebook, who has introduced a competing social media service called Threads. Mr. Musk has also called for in-person conflict, threatening this week to show up at Mr. Zuckerberg’s front door for a cage fight after the two billionaires had discussed a formal match but called it off.

“While we hope that Twitter will reverse its decision to institute a delay on Substack links, our focus is on building Substack,” the company’s founders, Chris Best, Hamish McKenzie and Jairaj Sethi, said in a statement about the throttling. “Substack was created in direct response to this kind of behavior by social media companies.”

In a post on Threads, Mr. Zuckerberg responded with a “thinking face emoji” to a post calling out the issue. Representatives for Meta, the parent company of Facebook, Instagram and Threads, did not immediately respond to a request for comment.

Charlie Stadtlander, a spokesman for The Times, said the company had not received an explanation about the delay, adding, “We would be concerned by targeted pressure applied to any news organization for unclear reasons.”

Social media services like YouTube and news outlets including CNN and The Washington Post appeared to have been unaffected by the throttling.

Mike Isaac, Justin Heideman and Hubert Mandeville contributed reporting.