Building Real-Time Collaborative Editors with CRDTs and WebSockets

Real-time collaboration is one of the most challenging features in modern web applications. This article walks through building a collaborative text editor from scratch using CRDTs (specifically Yjs) and WebSocket synchronization. We cover the theory behind CRDTs versus OT (Operational Transformation), implementing undo/redo in a distributed system, handling offline edits with local persistence, and scaling WebSocket connections using Redis Pub/Sub. The tutorial includes a complete React frontend with Yjs and a Node.js backend with ws and ioredis.