Hocuspocus is the WebSocket backend that turns a regular editor into a multiplayer one: two people open the same document, type at the same time, and watch each other's words appear in place, with every keystroke merged cleanly and no save conflicts to untangle later. The server speaks the Yjs synchronization protocol, so clients built with Tiptap, ProseMirror, Slate, Quill, or Monaco editors connect over a persistent connection and exchange small updates that the conflict-free data type orders correctly regardless of arrival sequence, and awareness messages carry cursor positions and presence so collaborators see who is in the document. Teams that outgrow one process add the Redis extension to balance connections across multiple server instances, reaching very large numbers of simultaneous editors on the same documents. Persistence extensions store documents in SQLite for small deployments or in a database or S3-compatible storage through your own fetch and store callbacks, the webhook extension notifies your application when documents change, throttling guards against abusive connections, and hooks for authentication and document loading let you enforce per-document permissions before anyone joins. Developers embed the server into an existing Node.js, Bun, Deno, or Cloudflare Workers runtime, or run it as the collaboration tier beside their main application, and offline-first clients queue changes locally and synchronize when the connection returns. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.