Threads, Meta’s text-based app to challenge Twitter, is now official. Mark Zuckerberg announced the new service one day ahead of the July 6th launch date that appeared in app stores earlier this week. Meta has begun rolling out the new service around the world, though it won’t be available within the European Union until the company addresses potential regulatory concerns.

In a blog post announcing the Twitter rival, the company described Threads as a “separate space for real-time updates and public conversations” that relies on users’ Instagram credentials but will eventually be compatible with a wider swath of decentralized services like Mastodon. For now though, Threads users log into the app and website with their existing Instagram account. The company will “carry over” existing usernames and verification status to Threads, though users have the option to further customize their profiles.

Like on Instagram, the company will rely heavily on recommendations to help people discover new accounts to follow. And Meta has been quietly testing the service with a small group of celebrities and creators, as well as its own employees, so new users won’t be greeted with an empty social network.

The service itself looks remarkably similar to Twitter though its design will feel familiar to Instagram users. It supports text posts up to 500 characters, as well as photos and videos up to five minutes. Threads will also support reposts — its version of a retweet — as well as quote posts. Users can also limit their replies, block and report other users. And posts from Threads can be easily shared to users’ Instagram Story for added visibility.

The launch comes at a particularly chaotic moment for Twitter, just days after Elon Musk announced strict rate limits that severely restricted the number of posts many users could view on the platform. The company also stopped showing tweets to logged-out users, before quietly backtracking. Musk, who has complained about AI companies training their platforms on Twitter data, blamed both unpopular moves on “data scraping.”

With Threads, Meta is challenging not just Twitter but the growing wave of Twitter alternatives like Mastodon. The company is planning to make Threads compatible with ActivityPub, the open source protocol that powers Mastodon and other decentralized services sometimes collectively referred to as the “Fediverse.”

“Our plan is to work with ActivityPub to provide you the option to stop using Threads and transfer your content to another service,” the company wrote in a blog post. “Our vision is that people using compatible apps will be able to follow and interact with people on Threads without having a Threads account, and vice versa, ushering in a new era of diverse and interconnected networks.”

As Meta explains, this means that users from Mastodon and other services that support ActivityPub will be able to follow and interact with public-facing posts on Threads. (Private accounts on threads will still be able to manually approve new followers from other services.) And other developers could one day create their own Threads-compatible features and services.

For now, it’s not clear how long it will take for Meta to fully integrate ActivityPub into Threads. In an early post on the service that was briefly viewable ahead of its official launch, Instagram head Adam Mosseri said the company was “committed” to the protocol, but didn’t provide a timeline. It’s also not clear how ActivityPub integration could affect content moderation and other safety issues. While Meta’s Threads app has the same content moderation policies as Instagram, services built by other developers are able to set their own standards and policies just as different instances on Mastodon have their own guidelines and norms. Meta notes that this will give users “the freedom to choose spaces that align with their values.”

At the moment, the biggest question facing Threads, though, is whether it has a chance at becoming a viable Twitter alternative. Since Musk took over the company last year, Twitter users have flocked to alternative platforms like Mastodon, Bluesky, T2, and others. But so far none have achieved anything close to the scale of Twitter, much less Meta. But, with more than 1 billion Instagram users, Zuckerberg and Meta are clearly hoping that they can gather momentum much more quickly than other decentralized upstarts.

“It’ll take some time, but I think there should be a public conversations app with 1 billion+ people on it,” Zuckerberg write in a post on Threads shortly after its launch. “Twitter has had the opportunity to do this but hasn’t nailed it. Hopefully we will.”

Update July 5th, 2023, 5:15 PM PT: This story has been updated to quote a post from Mark Zuckerberg’s Threads account.