xRegistry is a specification for a generic, extensible metadata registry and the HTTP API to query it. It defines a common resource model (“groups” containing “resources” with versioned “versions”) and a standard set of conventions for discovery, pagination, filtering, and references, so that different kinds of metadata registries all look the same from a client’s perspective.
On top of that core model, xRegistry defines domain-specific specs that instantiate it: the Schema Registry spec for managing JSON Schema, Avro, and Protobuf; the Message Definitions spec for CloudEvents and async message payloads; and the Endpoints spec for describing where producers and consumers can reach those messages. In practice that means a single API can serve schemas, event type definitions, and endpoint metadata in an interoperable way, rather than each tool inventing its own registry shape.
xRegistry is a CNCF sandbox project and is being driven by contributors from Microsoft, Google, and the CloudEvents community. The reference server is available at github.com/xregistry/server, and the specs cover both the wire format (JSON over HTTP) and filesystem representations so registries can be checked into Git.