ATProto Has No Instances, Unlike Mastodon
Original: There are no instances in ATProto
Why This Matters
Clarifies core architectural difference between decentralized protocols, essential for developers and users evaluating Bluesky and ATProto technology.
Article clarifies fundamental architecture difference: ATProto does not use instances like Mastodon's federated model. Author explains ATProto separates hosting and aggregation, similar to RSS/blogging infrastructure, contrasting with Mastodon's instance-based federation approach.
A blog post on overreacted.io addresses a recurring misconception about ATProto, the protocol powering Bluesky. The author explains that ATProto fundamentally differs from Mastodon's architecture. Mastodon uses "instances"—self-hosted communities functioning as independent social networks that federate with each other through message-passing between servers. Users belong to specific instances and must choose which instance's administrators to trust. ATProto instead separates hosting and aggregation as distinct layers, similar to RSS and blogging platforms. In this model, users can host their data independently while aggregation apps serve as "projections" of the underlying network without controlling user identity or data. The author traces the evolution from RSS/blogging (separated hosting and aggregation), to Facebook (centralized), to Mastodon (federated instances), positioning ATProto as a return to the hosting-aggregation separation principle. The distinction matters because asking "where are ATProto instances?" is a category error—ATProto simply does not implement the instance model.