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Bluesky is the social app with the features explained in Section 2, while the AT Protocol is the underlying decentralized foundation. We maintain this separation because the AT Protocol is designed to support multiple social modes, not just Bluesky. For example, besides a Twitter-style microblogging app, atproto could also be used to implement Reddit-style forums, long-form blogs with comments, or domain-specific social applications such as link sharing or book reviews. The same user identity, social graph, and user data storage servers can be shared between all of these apps.
- Post-Publication Addition: Several of the described social modes have been implemented by independent developers:
- Current Ecosystem Status: A unified social graph for AT Protocol applications has not yet appeared. Several apps currently use Bluesky's social graph to some degree, and nearly all apps use Bluesky's profile data directly.
The biggest constraint for new social modes is that atproto is currently designed for content that users want to make public. In particular, Bluesky user profiles, posts, follows, and likes are all public. Blocking actions are also currently public; we are investigating mechanisms for making these private. Only a small amount of user state is currently private: muted accounts and threads, notifications and their unread status, and user preferences such as content filtering settings. Private communications (direct messages) are currently handled by a centralized service run by Bluesky Social PBC; we plan to decentralize this component in the future.
- Post-Publication Addition: Private user data has been described in a series of blog posts by @dholms.at, Head of Protocol at Bluesky PBC. Additionally, active development of an implementation of private user data is ongoing, with an informal "big picture" specification available in the same branch.
- Current Ecosystem Status: A number of community proposals regarding private user data have been published: