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Build Status npm version

WebSocket support for Fastify built on the ws and uws libraries.


In server.js:

'use strict'

const fastify = require('fastify')()


fastify.ready(err => {
  if (err) throw err

  console.log('Server started.')
    .on('connection', socket => {
      console.log('Client connected.')

      socket.on('message', msg => socket.send(msg)) // Creates an echo server

      socket.on('close', () => console.log('Client disconnected.'))


Then run node server.js and navigate to http://localhost:34567 in your browser. In the browser's JavaScript console, open a client-side WebSocket connection:

const host = location.origin.replace(/^http/, 'ws')
const ws = new WebSocket(host)
ws.onmessage = msg => console.log(

Then, still in the browser console, send some messages to the server and watch as they're echoed back to you:

ws.send('WebSockets are awesome!')
// => undefined
// LOG: WebSockets are awesome!


The creator of uws has ceased development on uws and started working on their new project, uWebSockets.js. If you want high-performance web socket support in Fastify, the last real release of uws (10.148.1) is probably your best bet, but given that it is now an abandoned project I can't recommend anyone use it for any non-throwaway projects. If you're using this library, I'd recommend you stick with the default ws option.

In addition, if you choose to use uws as your WebSocket library, ensure that you have configured your system properly and understand that the API is a slightly reduced subset of ws's.


Licensed under MIT.