The AT Protocol (Authenticated Transfer Protocol), also commonly abbreviated as ATProto, is an open communications protocol intended to be used for decentralized social networking services.
ATProto began as the "Authenticated Data Experiment" (ADX), a project within Twitter to explore the possibility of decentralizing the platform. The protocol was designed to adress various issues with other:
The AT Protocol aims to solve these issues by splitting the services necessary for modern social media platforms into independently run microservices: Specifically, it splits up data storage, indexing, and social platforms into 3 core components:
PDSes store user data, posts, likes, etc. in Personal Data Repositories, commonly referred to as repos. PDSes serve as the access point for users, allowing users to add or remove records from their repos. They also serve repository updates to other network services.
Relays act as the core indexing mechanism for the protocol, crawling PDSes for repository updates, creating a repository of all network records, and forwarding repository updates to network services through federated network-wide data streams collectively termed the Firehose.
AppViews are end-user platforms and services which consume, process, and serve content from the Firehose to user clients. AppViews query user PDSes on the user's behalf, allowing users to update their repos and interact with content within the network.
The protocol allows for integration of peripheal services for additional customization of the user's experience.