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10.2.5 • Public • Published

WebRTC connector for Yjs

Propagates document updates peer-to-peer to all users using WebRTC.

  • Fast message propagation
  • Encryption and authorization over untrusted signaling servers
  • No setup required, public signaling servers are available
  • Very little server load
  • Not suited for a large amount of collaborators on a single document (each peer is connected to each other)



npm i y-webrtc

Client code

import * as Y from 'yjs'
import { WebrtcProvider } from 'y-webrtc'

const ydoc = new Y.Doc()
// clients connected to the same room-name share document updates
const provider = new WebrtcProvider('your-room-name', ydoc, { password: 'optional-room-password' })
const yarray = ydoc.get('array', Y.Array)


The peers find each other by connecting to a signaling server. This package implements a small signaling server in ./bin/server.js.

# start signaling server
PORT=4444 node ./bin/server.js

Peers using the same signaling server will find each other. You can specify several custom signaling servers like so:

const provider = new WebrtcProvider('your-room-name', ydoc, { signaling: ['wss://y-webrtc-ckynwnzncc.now.sh', 'ws://localhost:4444'] })

There is also an interesting article about setting up a scalable "serverless" signaling server by Ronny Roeller: https://medium.com/collaborne-engineering/serverless-yjs-72d0a84326a2

Communication Restrictions

y-webrtc is restricted by the number of peers that the web browser can create. By default, every client is connected to every other client up until the maximum number of conns is reached. The clients will still sync if every client is connected at least indirectly to every other client. Theoretically, y-webrtc allows an unlimited number of users, but at some point it can't be guaranteed anymore that the clients sync any longer**. Because we don't want to be greedy, y-webrtc has a restriction to connect to a maximum of 20 + math.floor(random.rand() * 15) peers. The value has a random factor in order to prevent clients to form clusters, that can't connect to other clients. The value can be adjusted using the maxConn option. I.e.

const provider = new WebrtcProvider('your-room-name', ydoc, { maxConns: 70 + math.floor(random.rand() * 70) })

** A gifted mind could use this as an exercise and calculate the probability of clusters forming depending on the number of peers in the network. The default value was used to connect at least 100 clients at a conference meeting on a bad network connection.

Use y-webrtc for conferencing solutions

Just listen to the "peers" event from the provider to listen for more incoming WebRTC connections and use the simple-peer API to share streams. More help on this would be welcome. By default, browser windows share data using BroadcastChannel without WebRTC. In order to connect all peers and browser windows with each other, set maxConns = Number.POSITIVE_INFINITY and filterBcConns = false.


new WebrtcProvider(roomName, ydoc[, opts])

The following default values of opts can be overwritten:

  // Specify signaling servers. The client will connect to every signaling server concurrently to find other peers as fast as possible.
  signaling: ['wss://signaling.yjs.dev', 'wss://y-webrtc-signaling-eu.herokuapp.com', 'wss://y-webrtc-signaling-us.herokuapp.com'],
  // If password is a string, it will be used to encrypt all communication over the signaling servers.
  // No sensitive information (WebRTC connection info, shared data) will be shared over the signaling servers.
  // The main objective is to prevent man-in-the-middle attacks and to allow you to securely use public / untrusted signaling instances.
  password: null,
  // Specify an existing Awareness instance - see https://github.com/yjs/y-protocols
  awareness: new awarenessProtocol.Awareness(doc),
  // Maximal number of WebRTC connections.
  // A random factor is recommended, because it reduces the chance that n clients form a cluster.
  maxConns: 20 + math.floor(random.rand() * 15),
  // Whether to disable WebRTC connections to other tabs in the same browser.
  // Tabs within the same browser share document updates using BroadcastChannels.
  // WebRTC connections within the same browser are therefore only necessary if you want to share video information too.
  filterBcConns: true,
  // simple-peer options. See https://github.com/feross/simple-peer#peer--new-peeropts for available options.
  // y-webrtc uses simple-peer internally as a library to create WebRTC connections.
  peerOpts: {}


y-webrtc uses the lib0/logging.js logging library. By default this library disables logging. You can enable it by specifying the log environment / localStorage variable:

// enable logging for all modules
localStorage.log = 'true'
// enable logging only for y-webrtc
localStorage.log = 'y-webrtc'
// by specifying a regex variables
localStorage.log = '^y.*'
# enable y-webrtc logging in nodejs
LOG='y-webrtc' node index.js


Yjs is licensed under the MIT License.




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