Yjs

The most-deployed JavaScript/TypeScript crdt|CRDT framework, designed for collaborative editing. The default sync layer for many local-first and real-time collab products.

What it gives you

• Shared data types — Y.Map, Y.Array, Y.Text, Y.XmlFragment, Y.XmlElement — that mutate locally and converge across replicas without coordination.
• YATA algorithm under the hood for sequence CRDTs (the text/array internals).
• Pluggable network providers — y-websocket, y-webrtc, y-leveldb, y-indexeddb. Compose persistence + transport.
• Editor bindings — first-class integration with ProseMirror, TipTap, Slate, Quill, Monaco, CodeMirror.
• Undo/redo manager that respects collaborative history.

When to pick Yjs over automerge

• Building a collaborative text editor → Yjs has the deepest editor ecosystem.
• Need rich-text with formatting (deltas, decorations) → YATA + editor bindings handle it.
• Want WebRTC peer-to-peer without a server → y-webrtc.

Pick automerge when the data model is document-shaped JSON (notes, designs, structured documents) and history/branching matters.

Used by

• Many local-first editors and SaaS collaboration features (Linear-style sync layers, collaborative IDEs).
• Mentioned in the CAP video as a representative of the modern partition-recovery toolchain alongside automerge.

See also

• crdt — the underlying theory
• automerge — the JSON-document alternative
• egwalker — newer text-CRDT algorithm Yjs’s YATA can be compared against
• local-first-software — the architecture Yjs enables