livekit-client

What is livekit-client?

The livekit-client npm package is a JavaScript client library for LiveKit, a platform that provides scalable WebRTC infrastructure for real-time audio and video communication. It allows developers to build applications with features like video conferencing, live streaming, and real-time data transmission.

What are livekit-client's main functionalities?

Connecting to a Room

This feature allows you to connect to a LiveKit room using a WebSocket URL and an access token. The code sample demonstrates how to establish a connection to a room, which is the first step in setting up a real-time communication session.

const { connect } = require('livekit-client');

async function joinRoom() {
  const room = await connect('ws://your-livekit-server', 'your-access-token');
  console.log('Connected to room', room.name);
}

joinRoom();

Publishing Local Tracks

This feature allows you to publish local audio and video tracks to a LiveKit room. The code sample shows how to create local media tracks and publish them, enabling other participants in the room to receive the media streams.

const { createLocalTracks } = require('livekit-client');

async function publishTracks(room) {
  const tracks = await createLocalTracks({ audio: true, video: true });
  tracks.forEach(track => room.localParticipant.publishTrack(track));
  console.log('Published local tracks');
}

// Assume room is already connected
publishTracks(room);

Subscribing to Remote Tracks

This feature allows you to subscribe to remote tracks published by other participants in the room. The code sample demonstrates how to handle the 'trackSubscribed' event to receive and play remote media streams.

room.on('trackSubscribed', (track, publication, participant) => {
  console.log('Subscribed to track', track.sid);
  // Attach track to a video element
  const videoElement = document.createElement('video');
  videoElement.srcObject = new MediaStream([track.mediaStreamTrack]);
  document.body.appendChild(videoElement);
  videoElement.play();
});

Other packages similar to livekit-client

simple-peer

simple-peer is a lightweight library for WebRTC peer-to-peer connections. It provides a simpler API for establishing WebRTC connections compared to livekit-client, but lacks the built-in server infrastructure and scalability features of LiveKit.

mediasoup-client

mediasoup-client is a client library for mediasoup, a WebRTC SFU (Selective Forwarding Unit). It offers advanced features for real-time media streaming and is highly customizable, but requires more setup and configuration compared to the more straightforward livekit-client.

twilio-video

twilio-video is a client library for Twilio's video API, providing similar functionalities for video conferencing and real-time communication. It offers robust support and integration with Twilio's ecosystem, but may come with higher costs compared to LiveKit's open-source model.

README

JavaScript/TypeScript client SDK for LiveKit

Use this SDK to add realtime video, audio and data features to your JavaScript/TypeScript app. By connecting to LiveKit Cloud or a self-hosted server, you can quickly build applications such as multi-modal AI, live streaming, or video calls with just a few lines of code.

Docs

Docs and guides at https://docs.livekit.io

SDK reference

[!NOTE] This is v2 of livekit-client. When migrating from v1.x to v2.x you might encounter a small set of breaking changes. Read the migration guide for a detailed overview of what has changed.

Installation

Yarn

yarn add livekit-client

NPM

npm install livekit-client --save

Minified JS

To use the SDK without a package manager, you can include it with a script tag:

<script src="https://cdn.jsdelivr.net/npm/livekit-client/dist/livekit-client.umd.min.js"></script>

The module will be exported under LivekitClient in the global namespace. When accessing symbols from the class, you'd need to prefix them with LivekitClient.. For example, Room becomes LivekitClient.Room.

Usage

Examples below are in TypeScript, if using JS/CommonJS imports replace import with:

const livekit = require('livekit-client');

const room = new livekit.Room(...);

// call this some time before actually connecting to speed up the actual connection
room.prepareConnection(url, token);

await room.connect(...);

Connecting to a room, publish video & audio

import {
  LocalParticipant,
  LocalTrackPublication,
  Participant,
  RemoteParticipant,
  RemoteTrack,
  RemoteTrackPublication,
  Room,
  RoomEvent,
  Track,
  VideoPresets,
} from 'livekit-client';

// creates a new room with options
const room = new Room({
  // automatically manage subscribed video quality
  adaptiveStream: true,

  // optimize publishing bandwidth and CPU for published tracks
  dynacast: true,

  // default capture settings
  videoCaptureDefaults: {
    resolution: VideoPresets.h720.resolution,
  },
});

// pre-warm connection, this can be called as early as your page is loaded
room.prepareConnection(url, token);

// set up event listeners
room
  .on(RoomEvent.TrackSubscribed, handleTrackSubscribed)
  .on(RoomEvent.TrackUnsubscribed, handleTrackUnsubscribed)
  .on(RoomEvent.ActiveSpeakersChanged, handleActiveSpeakerChange)
  .on(RoomEvent.Disconnected, handleDisconnect)
  .on(RoomEvent.LocalTrackUnpublished, handleLocalTrackUnpublished);

// connect to room
await room.connect('ws://localhost:7800', token);
console.log('connected to room', room.name);

// publish local camera and mic tracks
await room.localParticipant.enableCameraAndMicrophone();

function handleTrackSubscribed(
  track: RemoteTrack,
  publication: RemoteTrackPublication,
  participant: RemoteParticipant,
) {
  if (track.kind === Track.Kind.Video || track.kind === Track.Kind.Audio) {
    // attach it to a new HTMLVideoElement or HTMLAudioElement
    const element = track.attach();
    parentElement.appendChild(element);
  }
}

function handleTrackUnsubscribed(
  track: RemoteTrack,
  publication: RemoteTrackPublication,
  participant: RemoteParticipant,
) {
  // remove tracks from all attached elements
  track.detach();
}

function handleLocalTrackUnpublished(
  publication: LocalTrackPublication,
  participant: LocalParticipant,
) {
  // when local tracks are ended, update UI to remove them from rendering
  publication.track.detach();
}

function handleActiveSpeakerChange(speakers: Participant[]) {
  // show UI indicators when participant is speaking
}

function handleDisconnect() {
  console.log('disconnected from room');
}

In order to connect to a room, you need to first create an access token.

See authentication docs for details

Handling common track types

While LiveKit is designed to be flexible, we've added a few shortcuts that makes working with common track types simple. For a user's camera, microphone, and screen share, you can enable them with the following LocalParticipant methods:

const p = room.localParticipant;
// turn on the local user's camera and mic, this may trigger a browser prompt
// to ensure permissions are granted
await p.setCameraEnabled(true);
await p.setMicrophoneEnabled(true);

// start sharing the user's screen, this will trigger a browser prompt to select
// the screen to share.
await p.setScreenShareEnabled(true);

// disable camera to mute them, when muted, the user's camera indicator will be turned off
await p.setCameraEnabled(false);

Similarly, you can access these common track types on the other participants' end.

// get a RemoteParticipant by their identity
const p = room.remoteParticipants.get('participant-identity');
if (p) {
  // if the other user has enabled their camera, attach it to a new HTMLVideoElement
  if (p.isCameraEnabled) {
    const publication = p.getTrackPublication(Track.Source.Camera);
    if (publication?.isSubscribed) {
      const videoElement = publication.videoTrack?.attach();
      // do something with the element
    }
  }
}

Creating a track prior to creating a room

In some cases, it may be useful to create a track before creating a room. For example, when building a staging area so the user may check their own camera.

You can use our global track creation functions for this:

const tracks = await createLocalTracks({
  audio: true,
  video: true,
});

Publish tracks from any source

LiveKit lets you publish any track as long as it can be represented by a MediaStreamTrack. You can specify a name on the track in order to identify it later.

const pub = await room.localParticipant.publishTrack(mediaStreamTrack, {
  name: 'mytrack',
  simulcast: true,
  // if this should be treated like a camera feed, tag it as such
  // supported known sources are .Camera, .Microphone, .ScreenShare
  source: Track.Source.Camera,
});

// you may mute or unpublish the track later
pub.setMuted(true);

room.localParticipant.unpublishTrack(mediaStreamTrack);

Device management APIs

Users may have multiple input and output devices available. LiveKit will automatically use the one that's deemed as the default device on the system. You may also list and specify an alternative device to use.

We use the same deviceId as one returned by MediaDevices.enumerateDevices().

Example listing and selecting a camera device

// list all microphone devices
const devices = await Room.getLocalDevices('audioinput');

// select last device
const device = devices[devices.length - 1];

// in the current room, switch to the selected device and set
// it as default audioinput in the future.
await room.switchActiveDevice('audioinput', device.deviceId);

You can also switch devices given a constraint. This could be useful on mobile devices to switch to a back-facing camera:

await videoTrack.restartTrack({
  facingMode: 'environment',
});

Handling device failures

When creating tracks using LiveKit APIs (connect, createLocalTracks, setCameraEnabled, etc), it's possible to encounter errors with the underlying media device. In those cases, LiveKit will emit RoomEvent.MediaDevicesError.

You can use the helper MediaDeviceFailure.getFailure(error) to determine specific reason for the error.

• PermissionDenied - the user disallowed capturing devices
• NotFound - the particular device isn't available
• DeviceInUse - device is in use by another process (happens on Windows)

These distinctions enables you to provide more specific messaging to the user.

You could also retrieve the last error with LocalParticipant.lastCameraError and LocalParticipant.lastMicrophoneError.

Audio playback

Browsers can be restrictive with regards to audio playback that is not initiated by user interaction. What each browser considers as user interaction can vary by vendor (for example, Safari on iOS is very restrictive).

LiveKit will attempt to autoplay all audio tracks when you attach them to audio elements. However, if that fails, we'll notify you via RoomEvent.AudioPlaybackStatusChanged. Room.canPlaybackAudio will indicate if audio playback is permitted. LiveKit takes an optimistic approach so it's possible for this value to change from true to false when we encounter a browser error.

In the case user interaction is required, LiveKit provides Room.startAudio to start audio playback. This function must be triggered in an onclick or ontap event handler. In the same session, once audio playback is successful, additional audio tracks can be played without further user interactions.

room.on(RoomEvent.AudioPlaybackStatusChanged, () => {
  if (!room.canPlaybackAudio) {
    // UI is necessary.
    ...
    button.onclick = () => {
      // startAudio *must* be called in an click/tap handler.
      room.startAudio().then(() => {
        // successful, UI can be removed now
        button.remove();
      });
    }
  }
});

Configuring logging

This library uses loglevel for its internal logs. You can change the effective log level with the logLevel field in ConnectOptions. The method setLogExtension allows to hook into the livekit internal logs and send them to some third party logging service

setLogExtension((level: LogLevel, msg: string, context: object) => {
  const enhancedContext = { ...context, timeStamp: Date.now() };
  if (level >= LogLevel.debug) {
    console.log(level, msg, enhancedContext);
  }
});

RPC

Perform your own predefined method calls from one participant to another.

This feature is especially powerful when used with Agents, for instance to forward LLM function calls to your client application.

Registering an RPC method

The participant who implements the method and will receive its calls must first register support:

room.localParticipant?.registerRpcMethod(
  // method name - can be any string that makes sense for your application
  'greet',

  // method handler - will be called when the method is invoked by a RemoteParticipant
  async (data: RpcInvocationData) => {
    console.log(`Received greeting from ${data.callerIdentity}: ${data.payload}`);
    return `Hello, ${data.callerIdentity}!`;
  },
);

In addition to the payload, your handler will also receive responseTimeout, which informs you the maximum time available to return a response. If you are unable to respond in time, the call will result in an error on the caller's side.

Performing an RPC request

The caller may then initiate an RPC call like so:

try {
  const response = await room.localParticipant!.performRpc({
    destinationIdentity: 'recipient-identity',
    method: 'greet',
    payload: 'Hello from RPC!',
  });
  console.log('RPC response:', response);
} catch (error) {
  console.error('RPC call failed:', error);
}

You may find it useful to adjust the responseTimeout parameter, which indicates the amount of time you will wait for a response. We recommend keeping this value as low as possible while still satisfying the constraints of your application.

Errors

LiveKit is a dynamic realtime environment and calls can fail for various reasons.

You may throw errors of the type RpcError with a string message in an RPC method handler and they will be received on the caller's side with the message intact. Other errors will not be transmitted and will instead arrive to the caller as 1500 ("Application Error"). Other built-in errors are detailed in RpcError.

Error Codes

Code	Name	Reason
1	ConnectionError	0: NotAllowed 1: ServerUnreachable 2: InternalError 3: Cancelled 4:LeaveRequest
10	UnsupportedServer
12	UnexpectedConnectionState
13	NegotiationError
14	PublishDataError
15	SignalRequestError
20	TrackInvalidError
21	DeviceUnsupportedError
40	CryptorError

Examples

Demo App

examples/demo contains a demo webapp that uses the SDK. Run it with pnpm install && pnpm examples:demo

RPC Demo

examples/rpc contains a demo webapp that uses the SDK to showcase the RPC capabilities. Run it with pnpm install && pnpm dev from the examples/rpc directory.

Browser Support

Browser	Desktop OS	Mobile OS
Chrome	Windows, macOS, Linux	Android
Firefox	Windows, macOS, Linux	Android
Safari	macOS	iOS
Edge (Chromium)	Windows, macOS

We aim to support a broad range of browser versions by transpiling the library code with babel. You can have a look at the "browerslist" section of package.json for more details.

Note that the library requires some specific browser APIs to be present. You can check general compatibility with the helper function isBrowserSupported(). Support for more modern features like adaptiveStream and dynacast can be checked for with supportsAdaptiveStream() and supportsDynacast().

If you are targeting legacy browsers, but still want adaptiveStream functionality you'll likely need to use polyfills for ResizeObserver and IntersectionObserver.

Also when targeting legacy browsers, older than the ones specified in our browserslist target, make sure to transpile the library code to your desired target and include required polyfills with babel and/or corejs.

LiveKit Ecosystem
LiveKit SDKs	Browser · iOS/macOS/visionOS · Android · Flutter · React Native · Rust · Node.js · Python · Unity · Unity (WebGL)
Server APIs	Node.js · Golang · Ruby · Java/Kotlin · Python · Rust · PHP (community) · .NET (community)
UI Components	React · Android Compose · SwiftUI
Agents Frameworks	Python · Node.js · Playground
Services	LiveKit server · Egress · Ingress · SIP
Resources	Docs · Example apps · Cloud · Self-hosting · CLI

Changelog

2.9.8

Patch Changes

• Use string instead of passing url object to WebSocket constructor - #1443 (@davidliu)