It’s the latest move by Twitter’s new owner Elon Musk to crack down on certain speech after he shut down a Twitter account last week that was tracking the flights of his private jet.

“We know that many of our users may be active on other social media platforms; however, going forward, Twitter will no longer allow free promotion of specific social media platforms on Twitter,” the company said in a statement.

The banned platforms include mainstream websites such as Facebook and Instagram, and upstart rivals Mastodon, Tribel, Nostr, Post and former President Donald Trump’s Truth Social. Twitter gave no explanation for why the blacklist included those seven websites but not others such as Parler, TikTok or LinkedIn.

Twitter is also banning promotions of third-party social media link aggregators such as Linktree, which some people use to show where they can be found on different websites.

Twitter previously took action against one of the rivals, Mastodon, after its main Twitter account tweeted about the @ElonJet controversy last week. Mastodon has grown rapidly in recent weeks as an alternative for Twitter users who are unhappy with Musk’s overhaul of Twitter since he bought the company for $44 billion in late October and began restoring accounts that ran afoul of the previous Twitter leadership’s rules against hateful conduct and other harms.

Workarounds are banned, too

Some Twitter users have included links to their new Mastodon profile and encouraged followers to find them there. That’s now banned on Twitter, as are attempts to bypass restrictions such as by spelling out “instagram dot com” and a username instead of a direct website link.

Instagram and Facebook parent company Meta didn’t immediately return a request for comment Sunday.

Musk permanently banned the @ElonJet account on Wednesday, then changed Twitter’s rules to prohibit the sharing of another person’s current location without their consent. He then took aim at journalists who were writing about the jet-tracking account, which can still be found on other sites including Mastodon, Facebook, Instagram and Truth Social, alleging that they were broadcasting “basically assassination coordinates.”

Twitter last week suspended the accounts of numerous journalists who cover the social media platform and Musk, among them reporters working for The New York Times, Washington Post, CNN, Voice of America and other publications. Many of those accounts were restored following an online poll by Musk.

Then, over the weekend, The Washington Post’s Taylor Lorenz became the latest journalist to be temporarily banned from Twitter.

Lorenz said she and another Post technology reporter were researching an article concerning Musk. She had tried to communicate with the billionaire but the attempts went unanswered, so she tried to contact him Saturday by posting a message on Twitter tagging Musk and requesting an interview.

The specific topic was not disclosed in the tweet, although it was in response to Musk tweeting about an alleged incident earlier in the week involving a “violent stalker” in Southern California and Musk’s complaints about journalists allegedly revealing his family’s location by referencing the jet-tracker account.

When she went back later Saturday to check whether there was a response on Twitter, Lorenz was met with a notification that her account was “permanently suspended.”

“I won’t say I didn’t anticipate it,” Lorenz said in a phone interview early Sunday with The Associated Press. She said she wasn’t given a specific reason for the ban.

Sally Buzbee, The Washington Post’s executive editor, said in a written statement Sunday that the “arbitrary suspension of another Post journalist further undermines Elon Musk’s claim that he intends to run Twitter as a platform dedicated to free speech.

“Again, the suspension occurred with no warning, process or explanation — this time as our reporter merely sought comment from Musk for a story,” Buzbee said. “Post journalists should be reinstated immediately, without arbitrary conditions.“

By midday Sunday, Lorenz’s account was restored, as was the tweet she thought had triggered her suspension.