Since buying Twitter last year, Elon Musk has made a series of chaotic changes to the social media service that have alienated legions of users.

That’s been good news for Bluesky, an invite-only rival that has quickly gained a following since debuting in February. So far, its app has been downloaded 360,000 times from Apple’s app store worldwide, consumer data group Data.ai told Fortune, and over a million more users are on the waitlist to join. Most of the new users have been added in April, according to Bloomberg.

Bluesky was created by Jack Dorsey, who happens to also be Twitter’s co-founder. In contrast to Twitter, he wanted to build a decentralized service, meaning its user data is stored in independent servers rather than in ones owned by one company—thereby giving users more autonomy in how they interact on the platform.

“We envision an open social media ecosystem where developers have more opportunity to build and innovate, and users have more choice and control over which services they use and their experience on social media as a whole,” Jay Graber, CEO of Bluesky, wrote in a blog post last year.

Dorsey has said that one of his regrets was commercializing Twitter. If he had a chance to do it over again, he’d make it more like an open source project.

“The biggest issue and my biggest regret is that it [Twitter] became a company,” Dorsey tweeted in August, responding to a question about whether the platform turned out like he wanted it to.

Bluesky’s rise comes amid growing scrutiny over data security on social media sites as well as complaints about Twitter under Musk’s leadership. Those include Twitter requiring users to pay for blue check marks that signal their identities have been verified (these check marks were previously free) and then deciding to give away blue check marks to certain high-profile people (in some cases, dead people). Some recipients of free check marks are angry because the marks falsely make it appear as if they paid.

What Bluesky could offer

The origin story of Bluesky is closely linked to Twitter. It received its initial funding in 2021 from Twitter—Dorsey was the CEO until November of that year (it’s unclear exactly when the funding was received). Dorsey is also on Bluesky’s board. The service is still considered to be in a test phase and has a waitlist for users looking to join it. The timing of any broader rollout is unclear.

Bluesky didn’t immediately return Fortune’s request for comment.

Despite the deep links between the two social media apps, users’ search for an alternate social platform could be a direct result of Musk’s shake-up of Twitter. When Musk took over the company’s reins late last October, he fired top executives and, within weeks, half of the company’s staff. Twitter no longer has much of a content moderation team and, because of a lack of engineers, suffered occasional outages. The platform has become a breeding ground for hate speech and racist content, according to the Washington Post.

Bluesky isn’t the only alternative to Twitter that has gained momentum since Musk became the owner of a social media company. Mastodon, another decentralized service, founded in 2016, has grown rapidly. Shortly after Musk’s Twitter purchase, the number of Mastodon users increased sharply. They grew from 300,000 users in late October to 2.6 million at its peak in late November, Wired?reported. But that growth has been hard to sustain. By February, the number of downloads slumped as much as 99%.

Even with challenges, decentralized platforms could address some of the larger concerns over user data in the hands of individual companies—one of the key themes surrounding the Congressional hearing of TikTok in March.

“We believe decentralization is a means to end,” Graber wrote in a blog post in March. “The end goal is to provide choice to users, freedom to developers, and control to creators.”