What it is

PeerJS is an open-source library that provides a complete, configurable, and easy-to-use peer-to-peer API built on top of WebRTC. It lives in the JavaScript and TypeScript ecosystem, is written in TypeScript, and is distributed under the MIT license. The library supports both data channels and media streams, so applications can send arbitrary messages between browsers or negotiate audio and video calls without routing traffic through a central media server.

The concrete problem PeerJS solves is the complexity of raw WebRTC. Establishing a peer connection by hand requires signalling, session description negotiation, ICE candidate exchange, and careful browser-specific handling. PeerJS wraps that machinery behind a small API: a developer creates a Peer with an optional identifier, calls peer.connect for a data connection or peer.call for a media call, and listens for connection, data, call, and stream events. A companion project, PeerServer, handles the signalling broker that peers use to find one another.

Key capabilities

• Data connections between peers through peer.connect, with conn.send and a data event for receiving messages.
• Media calls through peer.call and call.answer, carrying audio and video streams obtained from navigator.mediaDevices.getUserMedia.
• Configurable peer identifiers, since a Peer can be constructed with a chosen id or left to receive a random one from the server.
• Support for CBOR and MessagePack serialization, which requires Firefox 102 or newer.
• Official browser support for Firefox 80+, Chrome 83+, Edge 83+, and Safari 15+, tested with BrowserStack.
• A documented API reference and a live example application that demonstrates both media and data connections.
• Distribution through npm and yarn as the peerjs package.

Who uses it and how

• Browser applications that need direct data exchange between clients, using the data connection API to send and receive messages.
• Video and audio calling features embedded in web apps, where the media call API negotiates streams between two peers.
• Developers following the live Glitch example, which combines media and data connections and runs against its own PeerServer instance.
• Teams that self-host the signalling layer by deploying PeerServer alongside their client application.
• Projects building on the Parcel and Webpack toolchains, with the caveat that Webpack emits a non-critical "request of a dependency is an expression" warning related to Parcel.

Getting started

Install with npm install peerjs or yarn add peerjs, then import Peer and construct an instance with an id or without one. Tests run with npm test, and a hosted PeerServer is available for signalling.

When to use it — and when not to

PeerJS is a strong fit when a project needs WebRTC peer connections without writing signalling and negotiation code by hand, and it remains actively maintained after fourteen years. A self-hoster must operate a PeerServer instance for signalling, which is a separate repository from the client library. The library carries 201 open issues and officially supports only recent browser versions, so older browsers and unsupported environments are outside its tested scope

// The usage -
import { Peer } from "peerjs";

const peer = new Peer("pick-an-id");
// You can pick your own id or omit the id if you want to get a random one from the server.

const conn = peer.connect("another-peers-id");
conn.on("open", () => {
	conn.send("hi!");
});

peer.on("connection", (conn) => {
	conn.on("data", (data) => {
		// Will print 'hi!'
		console.log(data);
	});
	conn.on("open", () => {
		conn.send("hello!");
	});
});

navigator.mediaDevices.getUserMedia(
	{ video: true, audio: true },
	(stream) => {
		const call = peer.call("another-peers-id", stream);
		call.on("stream", (remoteStream) => {
			// Show stream in some <video> element.
		});
	},
	(err) => {
		console.error("Failed to get local stream", err);
	},
);

peer.on("call", (call) => {
	navigator.mediaDevices.getUserMedia(
		{ video: true, audio: true },
		(stream) => {
			call.answer(stream); // Answer the call with an A/V stream.
			call.on("stream", (remoteStream) => {
				// Show stream in some <video> element.
			});
		},
		(err) => {
			console.error("Failed to get local stream", err);
		},
	);
});

npm test