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feross / webtorrent


⚡️ Streaming torrent client for the web



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Streaming torrent client for node & the browser

WebTorrent is a streaming torrent client for node.js and the browser. YEP, THAT'S RIGHT. THE BROWSER. It's written completely in JavaScript – the language of the web – so the same code works in both runtimes.

In node.js, this module is a simple torrent client, using TCP and UDP to talk to other torrent clients.

In the browser, WebTorrent uses WebRTC (data channels) for peer-to-peer transport. It can be used without browser plugins, extensions, or installations. It's Just JavaScript™.

Simply include the webtorrent.min.js script on your page to start fetching files over WebRTC using the BitTorrent protocol, or require('webtorrent') with browserify. See demo apps and code examples below.

To make BitTorrent work over WebRTC (which is the only p2p transport that works on the web) we made some protocol changes. Therefore, a browser-based WebTorrent client or "web peer" can only connect to other clients that support WebTorrent/WebRTC.

To seed files to web peers, use a client that supports WebTorrent, e.g. webtorrent-hybrid or We're also working on, a desktop client with a familiar UI that can connect to web peers. We hope established torrent clients (Transmission, Vuze, uTorrent, etc.) will add support for WebTorrent so they too can connect to both normal and web peers.


Warning: This is alpha software. Watch/star to follow along with progress.


  • Torrent client for node.js & the browser (same npm module!)
  • Insanely fast
  • Download multiple torrents simultaneously, efficiently
  • Pure Javascript (no native dependencies)
  • Exposes files as streams
    • Fetches pieces from the network on-demand so seeking is supported (even before torrent is finished)
    • Seamlessly switches between sequential and rarest-first piece selection strategy
  • Supports advanced torrent client features
  • Comprehensive test suite (runs completely offline, so it's reliable and fast)

Browser-only features

  • WebRTC data channels for lightweight peer-to-peer communication with no plugins
  • No silos. WebTorrent is a P2P network for the entire web. WebTorrent clients running on one domain can connect to clients on any other domain.
  • Stream video torrents into a <video> tag (webm (vp8, vp9) or mp4 (h.264))
  • Supports Chrome, Firefox, and Opera.

Sauce Test Status

Node-only features

  • Stream to AirPlay, Chromecast, VLC player, and many other devices/players

NOTE: To connect to "web peers" (browsers) in addition to normal BitTorrent peers, use webtorrent-hybrid which includes WebRTC support for node.


To install WebTorrent for use in node or the browser with require('webtorrent'), run:

npm install webtorrent

To install a webtorrent command line program, run:

npm install webtorrent -g

Ways to help

WebTorrent in production


WebTorrent is the first BitTorrent client that works in the browser, using open web standards (no plugins, just HTML5 and WebRTC)! It's easy to get started!

In the browser

Downloading a file is simple:
var WebTorrent = require('webtorrent')

var client = new WebTorrent()
var magnetUri = '...'

client.add(magnetUri, function (torrent) {
  // Got torrent metadata!
  console.log('Client is downloading:', torrent.infoHash)

  torrent.files.forEach(function (file) {
    // Display the file by appending it to the DOM. Supports video, audio, images, and
    // more. Specify a container element (CSS selector or reference to DOM node).
Seeding a file is simple, too:
var dragDrop = require('drag-drop')
var WebTorrent = require('webtorrent')

var client = new WebTorrent()

// When user drops files on the browser, create a new torrent and start seeding it!
dragDrop('body', function (files) {
  client.seed(files, function onTorrent (torrent) {
    console.log('Client is seeding:', torrent.infoHash)

There are more examples in the examples folder.


WebTorrent works great with browserify, an npm module that let's you use node-style require() to organize your browser code and load modules installed by npm (as seen in the previous examples).

WebTorrent is also available as a standalone script (webtorrent.min.js) which exposes WebTorrent on the window object, so it can be used with just a script tag:

<script src="webtorrent.min.js"></script>

The WebTorrent script is also hosted on fast, reliable CDN infrastructure (Cloudflare and MaxCDN) for easy inclusion on your site:

<script src=""></script>

In node.js

WebTorrent also works in node.js, using the same npm module! It's mad science!

As a command line app

WebTorrent is available as a command line app. Here's how to use it:

$ npm install webtorrent -g
$ webtorrent --help

To download a torrent:

$ webtorrent magnet_uri

To stream a torrent to a device like AirPlay or Chromecast, just pass a flag:

$ webtorrent magnet_uri --airplay

There are many supported streaming options:

--airplay               Apple TV
--chromecast            Chromecast
--mplayer               MPlayer
--mpv                   MPV
--omx [jack]            omx [default: hdmi]
--vlc                   VLC
--xbmc                  XBMC
--stdout                standard out [implies --quiet]

In addition to magnet uris, webtorrent supports many ways to specify a torrent.


This API should work exactly the same in node and the browser. Open an issue if this is not the case.

client = new WebTorrent([opts])

Create a new WebTorrent instance.

If opts is specified, then the default options (shown below) will be overridden.

  dht: Boolean|Object,   // Enable DHT (default=true), or options object for DHT
  maxPeers: Number,      // Max number of peers to connect to per torrent (default=100)
  nodeId: String|Buffer, // DHT protocol node ID (default=randomly generated)
  peerId: String|Buffer, // Wire protocol peer ID (default=randomly generated)
  rtcConfig: Object,     // RTCPeerConnection configuration object (default=STUN only)
  tracker: Boolean,      // Whether or not to enable trackers (default=true)
  wrtc: Object           // Custom webrtc implementation (in node, specify the [wrtc]( package)

client.add(torrentId, [opts], [function ontorrent (torrent) {}])

Start downloading a new torrent. Aliased as

torrentId can be one of:

  • magnet uri (string)
  • torrent file (buffer)
  • info hash (hex string or buffer)
  • parsed torrent (from parse-torrent)
  • http/https url to a torrent file (string)
  • filesystem path to a torrent file (string)

If opts is specified, then the default options (shown below) will be overridden.

  announce: [],   // Torrent trackers to use (added to list in .torrent or magnet uri)
  path: String,   // Folder to download files to (default=`/tmp/webtorrent/`)
  store: Function // Custom chunk store (must follow [abstract-chunk-store]( API)

If ontorrent is specified, then it will be called when this torrent is ready to be used (i.e. metadata is available). Note: this is distinct from the 'torrent' event which will fire for all torrents.

If you want access to the torrent object immediately in order to listen to events as the metadata is fetched from the network, then use the return value of client.add. If you just want the file data, then use ontorrent or the 'torrent' event.

client.seed(input, [opts], [function onseed (torrent) {}])

Start seeding a new torrent.

input can be any of the following:

  • path to the file or folder on filesystem (string)
  • W3C File object (from an <input> or drag and drop)
  • W3C FileList object (basically an array of File objects)
  • Node Buffer object (works in the browser)

Or, an array of string, File, or Buffer objects.

If opts is specified, it should contain the following types of options:

  • options for create-torrent (to allow configuration of the .torrent file that is created)
  • options for client.add (see above)

If onseed is specified, it will be called when the client has begun seeding the file.

client.on('torrent', function (torrent) {})

Emitted when a torrent is ready to be used (i.e. metadata is available and store is ready). See the torrent section for more info on what methods a torrent has.

client.remove(torrentId, [function callback (err) {}])

Remove a torrent from the client. Destroy all connections to peers and delete all saved file data. If callback is specified, it will be called when file data is removed.

client.destroy([function callback (err) {}])

Destroy the client, including all torrents and connections to peers. If callback is specified, it will be called when the client has gracefully closed.


An array of all torrents in the client.


Returns the torrent with the given torrentId. Convenience method. Easier than searching through the client.torrents array. Returns null if no matching torrent found.


Seed ratio for all torrents in the client.

torrent api


Get the info hash of the torrent.


Get the magnet URI of the torrent.


An array of all files in the torrent. See the file section for more info on what methods the file has.


The attached bittorrent-swarm instance.


Get total bytes received from peers (including invalid data)


Get total bytes received from peers (excluding invalid data)


Get the torrent download location


Alias for client.remove(torrent).


Adds a peer to the underlying bittorrent-swarm instance.

Returns true if peer was added, false if peer was blocked by the loaded blocklist., end, [priority], [notify])

Selects a range of pieces to prioritize starting with start and ending with end (both inclusive) at the given priority. notify is an optional callback to be called when the selection is updated with new data.

torrent.deselect(start, end, priority)

Deprioritizes a range of previously selected pieces.

torrent.critical(start, end)

Marks a range of pieces as critical priority to be downloaded ASAP. From start to end (both inclusive).


Create an http server to serve the contents of this torrent, dynamically fetching the needed torrent pieces to satisfy http requests. Range requests are supported.

Returns an http.Server instance (got from calling http.createServer). If opts is specified, it is passed to the http.createServer function.

Visiting the root of the server / will show a list of links to individual files. Access individual files at /<index> where <index> is the index in the torrent.files array (e.g. /0, /1, etc.)

Here is a usage example:

var client = new WebTorrent()
var magnetUri = '...'

client.add(magnetUri, function (torrent) {
  // create HTTP server for this torrent
  var server = torrent.createServer()
  server.listen(port) // start the server listening to a port

  // visit http://localhost:<port>/ to see a list of files

  // access individual files at http://localhost:<port>/<index> where index is the index
  // in the torrent.files array

  // later, cleanup...

torrent.on('done', function () {})

Emitted when all the torrent's files have been downloaded

Here is a usage example:

torrent.on('done', function(){
  console.log('torrent finished downloading');
     // do something with file

torrent.on('download', function (chunkSize) {})

Emitted every time a new chunk of data arrives, it's useful for reporting the current torrent status, for instance:

torrent.on('download', function(chunkSize){
  console.log('chunk size: ' + chunkSize);
  console.log('total downloaded: ' + torrent.downloaded);
  console.log('download speed: ' + torrent.downloadSpeed());
  console.log('progress: ' + torrent.progress);

torrent.on('wire', function (wire) {})

Emitted whenever a new peer is connected for this torrent. wire is an instance of bittorrent-protocol, which is a node.js-style duplex stream to the remote peer. This event can be used to specify custom BitTorrent protocol extensions.

Here is a usage example:

var MyExtension = require('./my-extension')

torrent1.on('wire', function (wire, addr) {
  console.log('connected to peer with address ' + addr)

See the bittorrent-protocol extension api docs for more information on how to define a protocol extension.

file api

File name, as specified by the torrent. Example: 'some-filename.txt'


File path, as specified by the torrent. Example: 'some-folder/some-filename.txt'


File length (in bytes), as specified by the torrent. Example: 12345

Selects the file to be downloaded, but at a lower priority than files with streams. Useful if you know you need the file at a later stage.


Deselects the file, which means it won't be downloaded unless someone creates a stream for it.

stream = file.createReadStream([opts])

Create a readable stream to the file. Pieces needed by the stream will be prioritized highly and fetched from the swarm first.

You can pass opts to stream only a slice of a file.

  start: startByte,
  end: endByte

Both start and end are inclusive.

file.getBuffer(function callback (err, buffer) {})

Get the file contents as a Buffer.

The file will be fetched from the network with highest priority, and callback will be called once the file is ready. callback must be specified, and will be called with a an Error (or null) and the file contents as a Buffer.

file.getBuffer(function (err, buffer) {
  if (err) throw err
  console.log(buffer) // <Buffer 00 98 00 01 01 00 00 00 50 ae 07 04 01 00 00 00 0a 00 00 00 00 00 00 00 78 ae 07 04 01 00 00 00 05 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ...>

file.appendTo(rootElem, function callback (err, elem) {})

Show the file in a the browser by appending it to the DOM. This is a powerful function that handles many file types like video (.mp4, .webm, .m4v, etc.), audio (.m4a, .mp3, .wav, etc.), images (.jpg, .gif, .png, etc.), and other file formats (.pdf, .md, .txt, etc.).

The file will be fetched from the network with highest priority and streamed into the page (if it's video or audio). In some cases, video or audio files will not be streamable because they're not in a format that the browser can stream so the file will be fully downloaded before being played. For other non-streamable file types like images and PDFs, the file will be downloaded then displayed.

rootElem is a container element (CSS selector or reference to DOM node) that the content will be shown in. A new DOM node will be created for the content and appended to rootElem.

callback will be called once the file is visible to the user. callback must be specified, and will be called with a an Error (or null) and the new DOM node that is displaying the content.

file.appendTo('#containerElement', function (err, elem) {
  if (err) throw err // file failed to download or display in the DOM
  console.log('New DOM node with the content', elem)

file.getBlobURL(function callback (err, url) {})

Get a url which can be used in the browser to refer to the file.

The file will be fetched from the network with highest priority, and callback will be called once the file is ready. callback must be specified, and will be called with a an Error (or null) and the Blob URL (String).

file.getBlobURL(function (err, url) {
  if (err) throw err
  var a = document.createElement('a') =
  a.href = url
  a.textContent = 'Download ' +


Most of the active development is happening inside of small npm modules which are used by WebTorrent.

The Node Way™

"When applications are done well, they are just the really application-specific, brackish residue that can't be so easily abstracted away. All the nice, reusable components sublimate away onto github and npm where everybody can collaborate to advance the commons." — substack from "how I write modules"

node.js is shiny


These are the main modules that make up WebTorrent:

module tests version description
webtorrent torrent client (this module)
bittorrent-dht distributed hash table client
bittorrent-peerid identify client name/version
bittorrent-protocol bittorrent protocol stream
bittorrent-swarm bittorrent connection manager
bittorrent-tracker bittorrent tracker server/client
create-torrent create .torrent files
ip-set efficient mutable ip set
load-ip-set load ip sets from local/network
magnet-uri parse magnet uris
parse-torrent parse torrent identifiers
torrent-discovery find peers via dht and tracker
ut_metadata metadata for magnet uris (ext)
ut_pex peer discovery (ext)


WebTorrent is an OPEN Open Source Project. Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit.

WebTorrent is only possible due to the excellent work of the following contributors:

Feross AboukhadijehGitHub/ferossTwitter/@feross
Daniel PoschGitHub/dcposchTwitter/@dcposch
John HieseyGitHub/jhieseyTwitter/@jhiesey
Travis FischerGitHub/fisch0920Twitter/@fisch0920
Iván TodorovichGitHub/ivantodorovichTwitter/@ivantodorovich
Mathias BuusGitHub/mafintoshTwitter/@mafintosh
Bob RenGitHub/bobrenjc93Twitter/@bobrenjc93

Clone the code

git clone
cd webtorrent
npm install
./bin/cmd.js --help

JavaScript Standard Style

WebTorrent uses JavaScript Standard Style.


Enable debug logs

In node, enable debug logs by setting the DEBUG environment variable to the name of the module you want to debug (e.g. bittorrent-protocol, or * to print all logs).

DEBUG=* webtorrent

Of course, this also works for the development version:

DEBUG=* ./bin/cmd.js

In the browser, enable debug logs by running this in the developer console:

localStorage.debug = '*'

Disable by running this:


Clone all dependencies

WebTorrent is a modular BitTorrent client, so functionality is split up into many npm modules. You can git clone all the relevant dependencies with one command. This makes it easier to send PRs:


Talks about WebTorrent

Known issues

Downloads don't start on Chromebook

Chromebooks are set to refuse all incoming connections by default. To change this, run:

sudo iptables -P INPUT ACCEPT


MIT. Copyright (c) Feross Aboukhadijeh.