AT Protocol

The AT Protocol is a shared rulebook that different social networks can adhere to. Such rulebooks are called protocols: they specify how programs exchange data with one another. In classic networks like Instagram, account, posts, and app all belong to a single company. The AT Protocol separates these three things. Your account and your posts reside at a location of your choosing, and the app is merely a view onto them. If you switch apps, you take your name and followers with you. The protocol has been developed since 2022 by a team around the Bluesky project.

What switching accounts without starting over changes

In today’s networks, moving is practically impossible. Anyone who leaves X loses their followers, their old posts, and their name. This dependency gives the platform a great deal of power. It can change rules, the amount of advertising, or prices, because no one can simply walk away. Experts call this effect lock-in.

The AT Protocol is meant to undo exactly that. Identity is not tied to the provider but to the user’s own identifier. This account comes with a digital key that can be used to prove posts are genuine. That’s why the word “Authenticated” appears in the name.

For companies and investors this is interesting because it shifts the business model. If users can leave at any time, a network becomes harder to monetize through coercion. Providers then have to win people over with better features instead. Whether this works economically remains an open question.

Data store, relay, and view

The protocol splits a social network into several building blocks. The first is the personal data store, known in technical jargon as the Personal Data Server. It holds your posts, likes, and your follower list. This store can sit with a company or on your own machine.

The second building block does the collecting: a so-called relay continuously reads out all open data stores. It bundles the new posts into one large stream of events. This resembles a news agency that pulls together reports from many sources. This stream is then further processed by services that build a view from it.

This view is what you see as an app: a timeline, search results, profiles. Because the data stream is open, anyone can offer their own views. This gives rise, for example, to self-built feeds with custom rules, such as showing only posts about astronomy. Moderation, too, is its own building block: filter lists can be subscribed to from independent providers. One important difference from Mastodon: there, you belong to a server, whereas here the server is merely a storage location.

Bluesky and what’s emerging alongside it

The protocol is most visible in Bluesky. The service launched in 2023 initially by invitation only and later grew to millions of accounts. At first glance it looks like Twitter. The difference lies underneath, in the shared data structure.

Further applications are emerging around the protocol. There are photo apps, blogging tools, and video services that use the same accounts. A profile created once works in all of them. Some users even link their account to their own web address as a display name.

Critical questions arise here in business news. Operating relays is expensive, because they process enormous amounts of data. Many such servers are currently run by the company behind Bluesky itself. A common misconception, therefore, is that the network is already fully decentralized. Technically, the openness is built in, but in practice much still rests with a single provider.