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y-sweet: a Yjs server with persistence and auth

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y-sweet is an open-source server for building realtime applications on top of the Yjs CRDT library.


  • Persists document data to a network filesystem or S3-compatible storage, inspired by Figma’s infrastructure.
  • Scales horizontally with a session backend model.
  • Deploys as a native Linux process, or as a WebAssembly module on Cloudflare's edge.
  • Provides document-level access control via client tokens.
  • Written in Rust with a focus on stability and performance, building on the blazing fast y-crdt library.

y-sweet stack

The y-sweet server can be used by any Yjs app, or you can use our opinionated stack to integrate Yjs and y-sweet into a Next.js app.

  • @y-sweet/sdk, a TypeScript library for interacting with y-sweet-server from your application backend.
  • @y-sweet/react, a React hooks library for building Yjs applications.
  • A debugger for exploring Yjs document and presence state.

The goal of the y-sweet stack is to give developers the end-to-end developer ergonomics they would expect from a proprietary state-sync platform, without the lock-in.

y-sweet is MIT-licensed, and was created by Jamsocket.



Explore our collaborative examples to help you get started.

All examples are open source and live in this repository, within /examples.


Check the vanilla js example for more details.

On the server

import { DocumentManager } from '@y-sweet/sdk'

// Pass in a CONNECTION_STRING, which you can get from running npx y-sweet@latest serve locally or from y-sweet cloud
const manager = new DocumentManager(CONNECTION_STRING)

// Get the client token from the y-sweet server. The client token is like the user's "password" to edit the "myDoc123" doc.
const clientToken = await manager.getOrCreateDocAndToken('myDoc123')

On the client

import * as Y from 'yjs';
import { createYjsProvider } from '@y-sweet/client';

// Create the yjs doc and link it to the y-sweet server:
const doc = new Y.Doc();
createYjsProvider(doc, clientToken);

// Now use the doc like a normal yjs doc!
let mySharedMap = doc.getMap('thing');
mySharedMap.set("foo", 123);

// Update your UI based on `mySharedMap` changes like this, for example:
mySharedMap.observe((event) => {
  event.keysChanged.forEach((key) => {
    // do whatever you want based on the detected change:
    yourUpdateFunction(key, mySharedMap.get(key));



Package Manager Name Version Path
npm y-sweet npm js-pkg/server y-sweet crates/y-sweet y-sweet-core crates/y-sweet-core


Package Manager Name Version Path
npm @y-sweet/sdk npm js-pkg/sdk
npm @y-sweet/react npm js-pkg/react

Y-Sweet Cloud

If you were to use the open source y-sweet server alone, you would still have to set up the infrastructure for self hosting it. With Y-Sweet cloud, every document is automatically persisted. You can link your own S3-compatible storage, or just let us take care of the details.

You can try a preview for free today by following our quickstart guide.

If you are interested in being a build partner for early access to new features, please reach out.

We are committed to growing y-sweet as an open-source-first project, wherever you decide to host it.