The WebSocket API (WebSockets)

The WebSocket API is an advanced technology that makes it possible to open a two-way interactive communication session between the user's browser and a server. With this API, you can send messages to a server and receive event-driven responses without having to poll the server for a reply.

Note: While a WebSocket connection is functionally somewhat similar to standard Unix-style sockets, they are not related.

Interfaces

WebSocket
The primary interface for connecting to a WebSocket server and then sending and receiving data on the connection.
CloseEvent
The event sent by the WebSocket object when the connection closes.
MessageEvent
The event sent by the WebSocket object when a message is received from the server.

Tools

  • HumbleNet: A cross-platform networking library that works in the browser. It consists of a C wrapper around WebSockets and WebRTC that abstracts away cross-browser differences, facilitating the creation of multi-user networking functionality for games and other apps.
  • µWebSockets: Highly scalable WebSocket server and client implementation for C++11 and Node.js.
  • ClusterWS:  Lightweight, fast and powerful framework for building scalable WebSocket applications in Node.js.
  • CWS: Fork of uWebSockets v0.14 with some minor tweaks in C++ code and complete rewrite of JavaScript code to TypeScript.
  • Socket.IO: A long polling/WebSocket based third party transfer protocol for Node.js.
  • SocketCluster: A pub/sub WebSocket framework for Node.js with a focus on scalability.
  • WebSocket-Node: A WebSocket server API implementation for Node.js.
  • Total.js: Web application framework for Node.js (Example: WebSocket chat)
  • Faye: A WebSocket (two-ways connections) and EventSource (one-way connections) for Node.js Server and Client.
  • SignalR: SignalR will use WebSockets under the covers when it's available, and gracefully fallback to other techniques and technologies when it isn't, while your application code stays the same.
  • Caddy: A web server capable of proxying arbitrary commands (stdin/stdout) as a websocket.
  • ws: a popular WebSocket client & server library for Node.js.
  • jsonrpc-bidirectional: Asynchronous RPC which, on a single connection, may have functions exported on the server and, and the same time, on the client (client may call server, server may also call client).
  • cowboy: Cowboy is a small, fast and modern HTTP server for Erlang/OTP with WebSocket support.

Specifications

Specification Status Comments
HTML Living Standard
The definition of 'WebSocket API' in that specification.
Living Standard  
WebSockets Candidate Recommendation  
RFC 6455: The WebSocket Protocol IETF RFC  

See also

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
WebSocketChrome Full support YesEdge Full support YesFirefox Full support 11
Notes
Full support 11
Notes
Notes See bug 695635.
No support 7 — 11
Prefixed Notes
Prefixed Implemented with the vendor prefix: Moz
Notes Message size limited to 16 MB (see bug 711205).
No support 4 — 6
Notes
Notes Message size limited to 16 MB (see bug 711205).
IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support 14
Notes
Full support 14
Notes
Notes See bug 695635.
No support 7 — 14
Prefixed Notes
Prefixed Implemented with the vendor prefix: Moz
Notes Message size limited to 16 MB (see bug 711205).
Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
WebSocket() constructorChrome Full support YesEdge ? Firefox Full support 7
Full support 7
No support 4 — 7
Notes
Notes Parameter protocols not supported.
IE ? Opera Full support YesSafari ? WebView Android Full support YesChrome Android Full support YesFirefox Android Full support 7Opera Android ? Safari iOS ? Samsung Internet Android ?
binaryTypeChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
bufferedAmountChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
closeChrome Full support YesEdge Full support 12Firefox Full support 8
Full support 8
No support 4 — 8
Notes
Notes Parameters not supported, see bug 674716.
IE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
close eventChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari ? WebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android ? Safari iOS ? Samsung Internet Android ?
error eventChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari ? WebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android ? Safari iOS ? Samsung Internet Android ?
extensionsChrome Full support YesEdge Full support 12Firefox Full support 8IE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support 8Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
message eventChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari ? WebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android ? Safari iOS ? Samsung Internet Android ?
oncloseChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
onerrorChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
onmessageChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
onopenChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
open eventChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari ? WebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android ? Safari iOS ? Samsung Internet Android ?
protocolChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
Supports protocol as specified by RFC 6455Chrome Full support 16Edge Full support 12Firefox Full support 11IE Full support 10Opera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 14Opera Android Full support 14Safari iOS Full support 6Samsung Internet Android ?
readyStateChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
sendChrome Full support YesEdge Full support 12Firefox Full support 18
Notes
Full support 18
Notes
Notes See bug 775368.
No support 11 — 18
Notes
Notes Only parameter of type ArrayBuffer and String supported.
No support 8 — 11
Notes
Notes Only parameter of type String supported.
No support 4 — 8
Notes
Notes Only parameter of type String supported. Returns boolean.
IE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
urlChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?
Available in workersChrome Full support YesEdge Full support YesFirefox Full support 37IE ? Opera ? Safari ? WebView Android Full support YesChrome Android Full support YesFirefox Android Full support 37Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.
Requires a vendor prefix or different name for use.
Requires a vendor prefix or different name for use.