What Is FlyWeb?

FlyWeb is a project at Mozilla focused on bringing a new set of APIs to the browser for advertising and discovering local-area web servers.

Draft Spec Mozilla Wiki

Getting Started

Setting up Firefox Developer Edition (Aurora)

  1. Install Firefox Developer Edition for Desktop or Firefox Aurora for Android

  2. Navigate to about:config and toggle on dom.flyweb.enabled

  3. On Desktop, select Customize from the ... menu and drag the FlyWeb icon to any toolbar

    Desktop Screenshot

    On Android, tap FlyWeb from the ... menu or enter about:flyweb in the address bar

    Android Screenshot

Publishing a server from a web page

The easiest way to get started building FlyWeb-enabled apps is via the FlyWeb Web API. This allows ordinary web pages to start local web servers and advertise them as FlyWeb services to nearby browsers.

navigator.publishServer('Hello FlyWeb').then(function(server) {
  server.onfetch = function(event) {
    var html = '<h1>Hello FlyWeb!</h1>' +
               '<h3>You requested: ' + event.request.url + '</h3>';

    event.respondWith(new Response(html, {
      headers: { 'Content-Type': 'text/html' }

In the example above, a FlyWeb service will be advertised called "Hello FlyWeb" that will respond with a simple HTML page that echoes the URL requested by the connected client.

Building a FlyWeb service on a Raspberry Pi

Because FlyWeb services are just local web servers, building a FlyWeb-enabled device with a Raspberry Pi is easy. Since Node.js can run on a Raspberry Pi, its possible to leverage the existing Node.js ecosystem for building server-side web applications including frameworks such as Express. The only additional functionality required to make an ordinary Node.js web server a FlyWeb service is a proper mDNS advertisement. Fortunately, an NPM module called mdns already exists for handling this important detail.

var http = require('http');
var mdns = require('mdns');

var port = parseInt(process.env.PORT || '3000');

var server = http.createServer(function(request, response) {
  var html = '<h1>Hello FlyWeb from Node JS!</h1>' +
             '<h3>You requested: ' + request.url + '</h3>';

  response.writeHead(200, { 'Content-Type': 'text/html' });

var advertisement = mdns.createAdvertisement(mdns.tcp('flyweb'), port, {
  name: 'Hello Node FlyWeb'

server.listen(port, function() {
  console.log('Server listening on port ' + port);

This example can be run in Node.js on a Raspberry Pi (or a laptop computer) and will advertise a FlyWeb service called "Hello Node FlyWeb" that can be discovered by clients on the local network running Firefox with FlyWeb enabled.


We are excited to hear about your ideas for using FlyWeb in new and unique ways! Please drop us a line in any of these channels if you have any questions or need any help getting your projects off the ground.


Justin D'Arcangelo



Jonas Sicking