yjs

Yjs is a high-performance, open-source framework for building real-time collaborative applications using conflict-free replicated data types (CRDTs). It enables multiple clients to edit shared data concurrently and ensures convergence to a consistent state without centralized locking or manual conflict resolution.

At its core, Yjs provides a shared document (Y.Doc) and a collection of data types such as Y.Text, Y.Map, Y.Array, and Y.XmlFragment. Changes are captured as compact updates that can be encoded, transmitted, and applied by other clients. Updates can be generated with encodeStateAsUpdate or encodeStateVector and applied via doc.applyUpdate. Yjs supports offline editing and later synchronization when connections are restored.

The framework is transport-agnostic, with networking and presence handled by separate providers. Popular providers include y-websocket, which syncs documents over WebSocket connections, and y-webrtc, which enables peer-to-peer synchronization. The ecosystem also offers bindings to various editor ecosystems and frameworks, allowing Yjs data structures to back editors such as ProseMirror, CodeMirror, and Quill, among others.

Common use cases include collaborative text editors, shared structured documents, and real-time dashboards or data views. Yjs emphasizes low-latency updates, strong convergence guarantees, offline capability, and modularity, making it a widely adopted foundation for building web-based collaborative tools.