WebSocket

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The WebSocket object provides the API for creating and managing a WebSocket connection to a server, as well as for sending and receiving data on the connection.

To construct a WebSocket, use the WebSocket() constructor.

Constructor

WebSocket(url[, protocols])
Returns a newly created WebSocket object.

Constants

Constant Value
WebSocket.CONNECTING 0
WebSocket.OPEN 1
WebSocket.CLOSING 2
WebSocket.CLOSED 3

Properties

WebSocket.binaryType
The binary data type used by the connection.
WebSocket.bufferedAmount Read only
The number of bytes of queued data.
WebSocket.extensions Read only
The extensions selected by the server.
WebSocket.onclose
An event listener to be called when the connection is closed.
WebSocket.onerror
An event listener to be called when an error occurs.
WebSocket.onmessage
An event listener to be called when a message is received from the server.
WebSocket.onopen
An event listener to be called when the connection is opened.
WebSocket.protocol Read only
The sub-protocol selected by the server.
WebSocket.readyState Read only
The current state of the connection.
WebSocket.url Read only
The absolute URL of the WebSocket.

Methods

WebSocket.close([code[, reason]])
Closes the connection.
WebSocket.send(data)
Enqueues data to be transmitted.

Events

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.

close
Fired when a connection with a WebSocket is closed.
Also available via the onclose property
error
Fired when a connection with a WebSockethas been closed because of an error, such as when some data couldn't be sent.
Also available via the onerror property.
message
Fired when data is received through a WebSocket.
Also available via the onmessage property.
open
Fired when a connection with a WebSocketis opened.
Also available via the onopen property.

Examples

// Create WebSocket connection.
const socket = new WebSocket('ws://localhost:8080');

// Connection opened
socket.addEventListener('open', function (event) {
    socket.send('Hello Server!');
});

// Listen for messages
socket.addEventListener('message', function (event) {
    console.log('Message from server ', event.data);
});

Specifications

Specification Status
HTML Living Standard
The definition of 'WebSocket' in that specification.
Living Standard

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
WebSocketChrome Full support 4Edge Full support 12Firefox 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 10Opera Full support 12.1Safari Full support 5WebView Android Full support ≤37Chrome Android Full support 18Firefox 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).
No support 4 — 6
Notes
Notes Message size limited to 16 MB (see bug 711205).
Opera Android Full support 12.1Safari iOS Full support 4.2Samsung Internet Android Full support 1.0
WebSocket() constructorChrome Full support YesEdge Full support ≤79Firefox 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 Full support Yes
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 Full support Yes
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 Full support Yes
closeChrome Full support 4Edge Full support 12Firefox Full support 8
Full support 8
No support 4 — 8
Notes
Notes Parameters not supported, see bug 674716.
IE Full support 10Opera Full support 12.1Safari Full support 5WebView Android Full support ≤37Chrome Android Full support 18Firefox Android Full support 8
Full support 8
No support 4 — 8
Notes
Notes Parameters not supported, see bug 674716.
Opera Android Full support 12.1Safari iOS Full support 4.2Samsung Internet Android Full support 1.0
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 Full support Yes
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 Full support Yes
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 Full support Yes
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 Full support Yes
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 Full support Yes
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 Full support Yes
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 Full support Yes
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 Full support Yes
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 Full support Yes
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 Full support Yes
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 Full support 1.0
readyStateChrome Full support 43Edge Full support 12Firefox Full support 19IE Full support 10Opera Full support 30Safari Full support 10WebView Android Full support 43Chrome Android Full support 43Firefox Android Full support 19Opera Android Full support 30Safari iOS Full support 10Samsung Internet Android Full support 4.0
sendChrome Full support 4Edge 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 Full support 10Opera Full support 12.1Safari Full support 5WebView Android Full support ≤37Chrome Android Full support 18Firefox Android Full support 18
Notes
Full support 18
Notes
Notes See bug 775368.
No support 14 — 18
Notes
Notes Only parameter of type ArrayBuffer and String supported.
No support 8 — 14
Notes
Notes Only parameter of type String supported.
No support 4 — 8
Notes
Notes Only parameter of type String supported. Returns boolean.
Opera Android Full support 12.1Safari iOS Full support 4.2Samsung Internet Android Full support 1.0
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 Full support Yes
Available in workersChrome Full support YesEdge Full support ≤18Firefox Full support 37IE ? Opera ? Safari ? WebView Android Full support YesChrome Android Full support YesFirefox Android Full support 37Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes

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.

See also