Mr. Musk did not respond to requests for comment, and Meta declined to comment.
After Mr. Musk purchased Twitter, Mastodon was an alternative service that immediately attracted attention, known as a federated platform and functioning as a collection of social networks. Started in 2016 by Eugen Rochko, a software developer who is now 29, Mastodon by design cannot enforce a platform-wide policy on what posts to post or delete. And because Mastodon’s original source code is publicly available, anyone can create their own version of the service.
Since the beginning of last month, Mastodon’s accounts have grown nearly 33 percent to six million, according to federated platform guide Fediverse.party. Mastodon has no ads and continues to be largely crowdfunded. It has hired more employees and encouraged people to start their own versions of Mastodon.
Mastodon did not respond to requests for comment.
Last month, Hive Social, a social network founded in 2019, also more than doubled its number of users to 1.8 million. Its founder, Raluca Pop, 24, attributed some of the growth to fan communities, such as those for K-pop and “Star Wars,” moving away from Twitter and finding a new home on Hive Social.
The small company is trying to capitalize on the renewed interest in raising money and hiring more employees. Hive Social is funded by loans taken out by Ms. Pop, as well as $25,000 from a private investor and more than $300,000 from a crowdfunding campaign. It has four employees and hopes to hire content moderators and more engineers, Ms Pop said.
But as people have joined, the platform has had growing pains, including multiple accounts parts same username and people do not mark content that is unsafe for work. On Thursday, Hive Social temporarily closed its servers to address security issues, Ms. Pop said.
“Twitter is going through a lot of changes with the new leadership,” said Ms. Pop. “The timing of it is more or less flawless. Everything was lined up for us.”
More established social media companies also started capturing people who left Twitter.
Tumblr, the microblogging website, posted a “reasons to join Tumblr” wire about a week after Twitter’s acquisition by Mr. Musk. It also shared memes and tumblr to post about people leaving Twitter for Tumblr. Then it started selling “Important Blue Internet Checkmarks” for $7.99 — the same price as a monthly subscription to Twitter Blue, a service Mr. Musk has promoted where people pay for features, including a verification check.