WebRTC (Web Real-Time Communication) is a technology that enables Web applications and sites to capture and optionally stream audio and/or video media, as well as to exchange arbitrary data between browsers without requiring an intermediary. The set of standards that comprise WebRTC makes it possible to share data and perform teleconferencing peer-to-peer, without requiring that the user install plug-ins or any other third-party software.

WebRTC consists of several interrelated APIs and protocols which work together to achieve this. The documentation you'll find here will help you understand the fundamentals of WebRTC, how to set up and use both data and media connections, and more.

WebRTC concepts and usage

WebRTC serves multiple purposes; together with theMedia Capture and Streams API, they provide powerful multimedia capabilities to the Web, including support for audio and video conferencing, file exchange, screen sharing, identity management, and interfacing with legacy telephone systems including support for sendingDTMF (touch-tone dialing) signals. Connections between peers can be made without requiring any special drivers or plug-ins, and can often be made without any intermediary servers.

Connections between two peers are represented by theRTCPeerConnection interface. Once a connection has been established and opened usingRTCPeerConnection, media streams (MediaStreams) and/or data channels (RTCDataChannels) can be added to the connection.

Media streams can consist of any number of tracks of media information; tracks, which are represented by objects based on theMediaStreamTrack interface, may contain one of a number of types of media data, including audio, video, and text (such as subtitles or even chapter names). Most streams consist of at least one audio track and likely also a video track, and can be used to send and receive both live media or stored media information (such as a streamed movie).

You can also use the connection between two peers to exchange arbitrary binary data using theRTCDataChannel interface. This can be used for back-channel information, metadata exchange, game status packets, file transfers, or even as a primary channel for data transfer.

Interoperability

WebRTC is in general well supported in modern browsers, but some incompatibilities remain. Theadapter.js library is a shim to insulate apps from these incompatibilities.

WebRTC reference

Because WebRTC provides interfaces that work together to accomplish a variety of tasks, we have divided up the reference by category. Please see the sidebar for an alphabetical list.

Connection setup and management

These interfaces, dictionaries, and types are used to set up, open, and manage WebRTC connections. Included are interfaces representing peer media connections, data channels, and interfaces used when exchanging information on the capabilities of each peer in order to select the best possible configuration for a two-way media connection.

Interfaces

RTCPeerConnection

Represents a WebRTC connection between the local computer and a remote peer. It is used to handle efficient streaming of data between the two peers.

RTCDataChannel

Represents a bi-directional data channel between two peers of a connection.

RTCDataChannelEvent

Represents events that occur while attaching aRTCDataChannel to aRTCPeerConnection. The only event sent with this interface isdatachannel.

RTCSessionDescription

Represents the parameters of a session. EachRTCSessionDescription consists of a descriptiontype indicating which part of the offer/answer negotiation process it describes and of theSDP descriptor of the session.

RTCStatsReport

Provides information detailing statistics for a connection or for an individual track on the connection; the report can be obtained by callingRTCPeerConnection.getStats().

RTCIceCandidate

Represents a candidate Interactive Connectivity Establishment (ICE) server for establishing anRTCPeerConnection.

RTCIceTransport

Represents information about anICE transport.

RTCPeerConnectionIceEvent

Represents events that occur in relation to ICE candidates with the target, usually anRTCPeerConnection. Only one event is of this type:icecandidate.

RTCRtpSender

Manages the encoding and transmission of data for aMediaStreamTrack on anRTCPeerConnection.

RTCRtpReceiver

Manages the reception and decoding of data for aMediaStreamTrack on anRTCPeerConnection.

RTCTrackEvent

The interface used to represent atrack event, which indicates that anRTCRtpReceiver object was added to theRTCPeerConnection object, indicating that a new incomingMediaStreamTrack was created and added to theRTCPeerConnection.

RTCSctpTransport

Provides information which describes a Stream Control Transmission Protocol (SCTP) transport and also provides a way to access the underlying Datagram Transport Layer Security (DTLS) transport over which SCTP packets for all of anRTCPeerConnection's data channels are sent and received.

Events

bufferedamountlow

The amount of data currently buffered by the data channel—as indicated by itsbufferedAmount property—has decreased to be at or below the channel's minimum buffered data size, as specified bybufferedAmountLowThreshold.

close

The data channel has completed the closing process and is now in theclosed state. Its underlying data transport is completely closed at this point. You can be notifiedbefore closing completes by watching for theclosing event instead.

closing

TheRTCDataChannel has transitioned to theclosing state, indicating that it will be closed soon. You can detect the completion of the closing process by watching for theclose event.

connectionstatechange

The connection's state, which can be accessed inconnectionState, has changed.

datachannel

A newRTCDataChannel is available following the remote peer opening a new data channel. This event's type isRTCDataChannelEvent.

error

AnRTCErrorEvent indicating that an error occurred on the data channel.

error

AnRTCErrorEvent indicating that an error occurred on theRTCDtlsTransport. This error will be eitherdtls-failure orfingerprint-failure.

gatheringstatechange

TheRTCIceTransport's gathering state has changed.

icecandidate

AnRTCPeerConnectionIceEvent which is sent whenever the local device has identified a new ICE candidate which needs to be added to the local peer by callingsetLocalDescription().

icecandidateerror

AnRTCPeerConnectionIceErrorEvent indicating that an error has occurred while gathering ICE candidates.

iceconnectionstatechange

Sent to anRTCPeerConnection when its ICE connection's state—found in theiceConnectionState property—changes.

icegatheringstatechange

Sent to anRTCPeerConnection when its ICE gathering state—found in theiceGatheringState property—changes.

message

A message has been received on the data channel. The event is of typeMessageEvent.

negotiationneeded

Informs theRTCPeerConnection that it needs to perform session negotiation by callingcreateOffer() followed bysetLocalDescription().

open

The underlying data transport for theRTCDataChannel has been successfully opened or re-opened.

selectedcandidatepairchange

The currently-selected pair of ICE candidates has changed for theRTCIceTransport on which the event is fired.

track

Thetrack event, of typeRTCTrackEvent is sent to anRTCPeerConnection when a new track is added to the connection following the successful negotiation of the media's streaming.

signalingstatechange

Sent to the peer connection when itssignalingState has changed. This happens as a result of a call to eithersetLocalDescription() orsetRemoteDescription().

statechange

The state of theRTCDtlsTransport has changed.

statechange

The state of theRTCIceTransport has changed.

statechange

The state of theRTCSctpTransport has changed.

rtctransform

An encoded video or audio frame is ready to process using a transform stream in a worker.

Types

RTCSctpTransport.state

Indicates the state of anRTCSctpTransport instance.

Identity and security

These APIs are used to manage user identity and security, in order to authenticate the user for a connection.

RTCIdentityProvider

Enables a user agent is able to request that an identity assertion be generated or validated.

RTCIdentityAssertion

Represents the identity of the remote peer of the current connection. If no peer has yet been set and verified this interface returnsnull. Once set it can't be changed.

RTCIdentityProviderRegistrar

Registers an identity provider (idP).

RTCCertificate

Represents a certificate that anRTCPeerConnection uses to authenticate.

Telephony

These interfaces and events are related to interactivity with Public-Switched Telephone Networks (PSTNs). They're primarily used to send tone dialing sounds—or packets representing those tones—across the network to the remote peer.

Interfaces

RTCDTMFSender

Manages the encoding and transmission of Dual-Tone Multi-Frequency (DTMF) signaling for anRTCPeerConnection.

RTCDTMFToneChangeEvent

Used by thetonechange event to indicate that a DTMF tone has either begun or ended. This event does not bubble (except where otherwise stated) and is not cancelable (except where otherwise stated).

Events

tonechange

Either a newDTMF tone has begun to play over the connection, or the last tone in theRTCDTMFSender'stoneBuffer has been sent and the buffer is now empty. The event's type isRTCDTMFToneChangeEvent.

Encoded Transforms

These interfaces and events are used to process incoming and outgoing encoded video and audio frames using a transform stream running in a worker.

Interfaces

RTCRtpScriptTransform

An interface for inserting transform stream(s) running in a worker into the RTC pipeline.

RTCRtpScriptTransformer

The worker-side counterpart of anRTCRtpScriptTransform that passes options from the main thread, along with a readable stream and writeable stream that can be used to pipe encoded frames through aTransformStream.

RTCEncodedVideoFrame

Represents an encoded video frame to be transformed in the RTC pipeline.

RTCEncodedAudioFrame

Represents an encoded audio frame to be transformed in the RTC pipeline.

Properties

RTCRtpReceiver.transform

A property used to insert a transform stream into the receiver pipeline for incoming encoded video and audio frames.

RTCRtpSender.transform

A property used to insert a transform stream into the sender pipeline for outgoing encoded video and audio frames.

Events

rtctransform

An RTC transform is ready to run in the worker, or an encoded video or audio frame is ready to process.

Guides

Introduction to the Real-time Transport Protocol (RTP)

The Real-time Transport Protocol (RTP), defined inRFC 3550, is an IETF standard protocol to enable real-time connectivity for exchanging data that needs real-time priority. This article provides an overview of what RTP is and how it functions in the context of WebRTC.

Introduction to WebRTC protocols

This article introduces the protocols on top of which the WebRTC API is built.

WebRTC connectivity

A guide to how WebRTC connections work and how the various protocols and interfaces can be used together to build powerful communication apps.

Lifetime of a WebRTC session

WebRTC lets you build peer-to-peer communication of arbitrary data, audio, or video—or any combination thereof—into a browser application. In this article, we'll look at the lifetime of a WebRTC session, from establishing the connection all the way through closing the connection when it's no longer needed.

Establishing a connection: The perfect negotiation pattern

Perfect negotiation is a design pattern which is recommended for your signaling process to follow, which provides transparency in negotiation while allowing both sides to be either the offerer or the answerer, without significant coding needed to differentiate the two.

Signaling and two-way video calling

A tutorial and example which turns a WebSocket-based chat system created for a previous example and adds support for opening video calls among participants. The chat server's WebSocket connection is used for WebRTC signaling.

Codecs used by WebRTC

A guide to the codecs which WebRTC requires browsers to support as well as the optional ones supported by various popular browsers. Included is a guide to help you choose the best codecs for your needs.

Using WebRTC data channels

This guide covers how you can use a peer connection and an associatedRTCDataChannel to exchange arbitrary data between two peers.

Using DTMF with WebRTC

WebRTC's support for interacting with gateways that link to old-school telephone systems includes support for sending DTMF tones using theRTCDTMFSender interface. This guide shows how to do so.

Using WebRTC Encoded Transforms

This guide shows how a web application can modify incoming and outgoing WebRTC encoded video and audio frames, using aTransformStream running into a worker.

Tutorials

Improving compatibility using WebRTC adapter.js

The WebRTC organizationprovides on GitHub the WebRTC adapter to work around compatibility issues in different browsers' WebRTC implementations. The adapter is a JavaScript shim which lets your code to be written to the specification so that it will "just work" in all browsers with WebRTC support.

A simple RTCDataChannel sample

TheRTCDataChannel interface is a feature which lets you open a channel between two peers over which you may send and receive arbitrary data. The API is intentionally similar to theWebSocket API, so that the same programming model can be used for each.

Building an internet connected phone with Peer.js

This tutorial is a step-by-step guide on how to build a phone using Peer.js

Specifications

WebRTC-proper protocols

• Application Layer Protocol Negotiation for Web Real-Time Communications
• WebRTC Audio Codec and Processing Requirements
• RTCWeb Data Channels
• RTCWeb Data Channel Protocol
• Web Real-Time Communication (WebRTC): Media Transport and Use of RTP
• WebRTC Security Architecture
• Transports for RTCWEB

Related supporting protocols

• Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocol
• Session Traversal Utilities for NAT (STUN)
• URI Scheme for the Session Traversal Utilities for NAT (STUN) Protocol
• Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
• An Offer/Answer Model with Session Description Protocol (SDP)
• Session Traversal Utilities for NAT (STUN) Extension for Third Party Authorization

See also

• MediaDevices
• MediaStreamEvent
• MediaStreamTrack
• MessageEvent
• MediaStream
• Media Capture and Streams API
• Firefox multistream and renegotiation for Jitsi Videobridge
• Peering Through the WebRTC Fog with SocketPeer
• Inside the Party Bus: Building a Web App with Multiple Live Video Streams + Interactive Graphics
• Web media technologies