Yjs

Overview

Yjs is a library for building real-time collaborative multi-user applications. It exposes Shared Types that behave like normal data types but sync automatically across users and devices.

Unlike traditional approaches that require a central server for coordination, Yjs is network agnostic and works with any communication protocol. It is designed for developers building collaborative editors, whiteboards, note-taking apps, and any multi-user tool that needs real-time state synchronization.

Key Benefits

• Shared Types sync automatically across users without manual conflict resolution code.
• Offline support lets users edit locally and sync later when connectivity returns.
• Network agnostic design works without a central server, making systems faster and more fault tolerant.
• Over 900k weekly downloads make Yjs the most popular engine for building collaborative applications.
• Rich ecosystem of integrations with popular editor libraries and web frameworks.

How It Works

You define shared data types (like text, arrays, maps) that behave like normal JavaScript data types. Yjs uses a CRDT (Conflict-free Replicated Data Type) under the hood to automatically merge changes from multiple users without conflicts. You connect users through any transport layer — WebSocket, WebRTC, or Matrix — and Yjs handles the synchronization and conflict resolution.

Use Cases

• Collaborative document editors like Proton Docs, Evernote, and Gitbook use Yjs for real-time co-authoring.
• Project management platforms like ClickUp, Monday, and Shopify rely on Yjs for shared task boards and lists.
• Code editors and IDEs such as Eclipse Theia, Codeanywhere, and JupyterLab integrate Yjs for multi-user coding sessions.
• Note-taking apps including Joplin, Outline, Supernotes, and Affine use Yjs to sync notes across devices and users.
• Whiteboarding and drawing tools like the Yjs Drawing Demo enable real-time collaborative sketching.
• Cloud IDE and machine learning platforms like AWS SageMaker use Yjs for shared notebook environments.

Why Choose This Product

Yjs is best suited for developers who need to add real-time collaboration to web applications without building custom conflict resolution logic. It is open source, network agnostic, and has the largest ecosystem of integrations among collaborative CRDT libraries. The library is maintained by Kevin Jahns and supported by a community forum and Discord server.