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This repository hosts a community effort to implement experimental APIs for Firefox WebExtensions with a goal of enabling dweb protocols in Firefox through browser add-ons. The long term goal of this project is to integrate these APIs into the WebExtensions ecosystem.


You can help this effort in following ways:

  1. Use these APIs to make something illustrating its value, to build the case for adoption in the core WebExtension API set.
  2. Get involved in driving this effort: Help with an API implementation, maintenance, testing, code samples, etc.
  3. Help build API adapters to enable seamless integration with existing libraries.
  4. Join our IRC channel: #dweb on irc.mozilla.org

Status: In active development

API Status
Protocol Handler 🐥
Service Discovery 🐣
File System 🐣
UDP Socket 🐣
TCP Socket 🐣
  • 🥚 : In design phase
  • 🐣 : Work in progress
  • 🐥 : Try it out
  • 🐓 : Usable

API overview

Note: You can try all the examples after you've cloned the repo and got the toolchain setup by running npm install. You will also need Firefox Nightly to run the demos.

Protocol API

The Protocol API allows you to handle custom protocols from your Firefox extension. This is different from the existing WebExtensions protocol handler API in that it does not register a website for handling corresponding URLs but rather allows your WebExtension to implement the handler.

The following example implements a simple dweb:// protocol. When firefox is navigated to dweb://hello/world, for example, it will invoke your registered handler and pass it a request object containing request URL as request.url string property. Your handler is expected to return a repsonse with a content that is async iterator of ArrayBuffers. In our example we use a respond async generator function to respond with some HTML markup.

browser.protocol.registerProtocol("dweb", request => {
  return {
    contentType: "text/html",
    content: respond(request.url)

async function* respond(text) {
  const encoder = new TextEncoder("utf-8")
  yield encoder.encode("<h1>Hi there!</h1>\n").buffer
  yield encoder.encode(
    `<p>You've succesfully loaded <strong>${request.url}</strong><p>`

Given that response.content is an async iterator it is also possible to stream response content as this next example illustrates.

browser.protocol.registerProtocol("dweb", request => {
  switch (request.url) {
    case "dweb://stream/": {
      return {
        contentType: "text/html",
        content: streamRespond(request)
    default: {
      return {
        contentType: "text/html",
        content: respond(request.url)

async function* streamRespond(request) {
  const encoder = new TextEncoder("utf-8")
  yield encoder.encode("<h1>Say Hi to endless stream!</h1>\n").buffer
  let n = 0
  while (true) {
    await new Promise(resolve => setTimeout(resolve, 1000))
    yield encoder.encode(`<p>Chunk #${++n}<p>`).buffer

You can see the demo of the example above in Firefox Nightly by running following command, and then navigating to dweb://hello/world or dweb://stream/

npm run demo:protocol

protocol demo

Service Discovery API

API provides DNS-Based Service Discovery API as per rfc6763. Following example illustrates how this API can be used to discover available http services in the network.

void (async () => {
  const services = browser.ServiceDiscovery.discover({
    type: "dweb",
    protocol: "tcp" // Must be "tcp" or "udp"

  console.log("Start discovery", services.query)
  for await (const service of services) {
    if (service.lost) {
      console.log("Lost service", service)
    } else {
      console.log("Found service", {
        name: service.name,
        type: service.type,
        protocol: service.protocol

      for (const {
      } of await service.addresses()) {
          `Service ${service.name} available at ${host} ${address}:${port}`,
  console.log("End discovery", services.query)

API also allows you to announce service that others on the network can discover. Following example illustrates that:

void (async () => {
  const service = await browser.ServiceDiscovery.announce({
    name: "My dweb service",
    type: "dweb",
    protocol: "tcp", // must be "tcp" or "udp"
    port: 3000, // ommting port will just assign you available one.
    attributes: {
      // optional txt records
      version: "1.0."

  console.log("Service annouced", {
    name: service.name, // Note: Colud be different like "My dweb service (2)"
    type: service.type,
    protocol: service.protocol,
    port: service.port,
    attributes: service.attributes // Will be null if was omitted

  // Wait for a 1 minute and expire service announcement
  await new Promise(timeout => setTimeout(timeout, 60 * 1000))
  await service.expire()
  console.log(`Service expired`)


You can try demo WebExtension that discovers and displays http services in your local network when button in the toolbar is clicked. You can run it in Firefox Nightly via the following command

npm run demo:discovery

discovery button

FileSystem API

FileSystem API provides access to an OS file system, but restricted to a user chosen directory. Below example illustrates writing a content to a file in user chosen directory.

void (async () => {
  const volume = await browser.FileSystem.mount({
    read: true,
    write: true
  console.log("Mounted", volume)
  localStorage.setItem("volumeURL", volume.url)

  const fileURL = new URL("hello.md", volume.url).href
  const encoder = new TextEncoder()
  const content = encoder.encode("# Hello World\n").buffer
  const size = await browser.FileSystem.writeFile(fileURL, content)
  console.log(`Wrote ${size} bytes to ${fileURL}`)

Call to FileSystem.mount will notify user that corresponding WebExtension is requesting read / write access to the file system, which user can deny or grant by choosing a directory. If user denies to access then promise returned by mount will be rejected, if user chooses to grant access to a specific directory the promise will resolve to an object like:


The rest of the example that writes content into a file should be pretty straight forward.

Note: Granted access will be preserved across sessions, and WebExtension could mount same directory without prompting a user again.

Following is a more complete example that will either mount directory that user has already granted access to or request access to new directory otherwise.

void (async () => {
  const url = localStorage.getItem("volumeURL")
  const volume = await browser.FileSystem.mount({ url, read: true })

  const fileURL = new URL("hello.md", volume.url).href
  const file = await browser.FileSystem.open(fileURL, { read: true })
  const chunk = await browser.File.read(file, { position: 2, size: 5 })
  console.log(`Read file fragment from ${fileURL}`, chunk)
  const decoder = new TextDecoder()
  const content = decoder.decode(chunk)
  console.log(`Decode read fragment`, content)
  await browser.File.close(file)

Note: Attempting to mount a URL that user has not previously granted access to will fail without even prompting a user.

FileSystem API has many other functions available. You can follow the links for detailed API interface definitions of browser.FileSystem and browser.File

You can try demo WebExtension that provides a REPL in the sidebar exposing all of the FileSystem API, which you can run in Firefox Nightly via following command

Note: Commands recognized by REPL correspond to the API functions names and all the parameters are names prefixed by -- and followed by value.

npm run demo:fs



API provides an implementation of UDP Datagram sockets. Follow the link for detailed API interface for browser.UDPSocket which corresponds to UDPSocketManager.

There is also a @libdweb/dgram-adapter project that provides nodejs dgram API adapter.


Following example opens UDP socket on port 41234 that will act as a server and will continuously print incoming messages.

void (async () => {
  const server = await browser.UDPSocket.create({
    port: 41234
  console.log(`listening ${server.address.host}:${server.address.port}`)

  const decoder = new TextDecoder()
  for await (const { from, data } of browser.UDPSocket.messages(server)) {
    console.log(`receive message`)
    const message = decoder.decode(data)
    console.log(`server got: ${message} from ${from.host}:${from.port}`)

Note: Incoming messages are represented via async iterator which can be consumed via for await, but be aware that messages are not buffered so if you use await inside the for await block chances are you will miss message which will be dropped.

Following example opens socket on arbitrary port and then sends a message to the server socket from the above example.

void (async () => {
  const client = await browser.UDPSocket.create({ host: "" })
  console.log(`opened socket ${client.address.host}:${client.address.port}`)
  const encoder = new TextEncoder()
  const message = encoder.encode("Hello UDP").buffer
  await browser.UDPSocket.send(client, "", 41234, message)

Note: UDPSocket API unlike one in nodejs is not going to resolve hostnames like "localhost". You need to use WebExtensions dns API to resolve hostnames.


P2P Chat Demo

You can try demo WebExtension that uses UDP multicasting to do peer-to-peer chat in a firefox sidebar. You can run in Firefox Nightly via following command

Note: This is a demo illustrates UDP and Multicasting API.

npm run demo:p2p-chat



You can try demo WebExtension that provides a REPL in the sidebar exposing all of the UDPSocket API, which you can run in Firefox Nightly via following command

Note: Commands recognized by REPL correspond to the API functions names and all the parameters are names prefixed by -- and followed by corresponding values.

npm run demo:dgram


TCPSocket API provides a client and server socket APIs for TCP networking.


Following example starts echo TCP server on port 8090. It will accept incoming connections read first chunk of data, respond by echoing messages back to.

void (async () => {
  const encoder = new TextEncoder()
  const decoder = new TextDecoder()

  const server = await browser.TCPSocket.listen({ port: 8090 })
  console.log("Started TCP Server", server)

  const onconnect = async client => {
    console.log("Client connected:", client)
    const message = await client.read()
    console.log("Received message from client:", decoder.decode(message))
    const response = encoder.encode(`<echo>${decoder.decode(message)}</echo>`)
    await client.write(response.buffer)

  for await (const client of server.connections) {

Note: server.connections are represented via async iterator which can be consumed via for await, but be aware that connections are not buffered which is why handle each connection in onconnect function so our server can accept more connections. If you use await inside the for await block chances are you will miss connection, in which case it will be automatically closed.

Following example connects to server from the example above writes a message to it and then reads message received back.

void (async () => {
  const encoder = new TextEncoder()
  const decoder = new TextDecoder()

  const client = await browser.TCPSocket.connect({
    host: "localhost",
    port: 8090
  await client.opened
  console.log("Client connected:", client)

  await client.write(encoder.encode("Hello TCP").buffer)
  const response = await client.read()
  console.log("Received response:", decoder.decode(response))



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