Web/API/WebSocket

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 WebSocket has 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 WebSocket is 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 StandardThe definition of 'WebSocket' in that specification.	Living Standard

Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
WebSocket	Chrome Full support 4	Edge Full support 12	Firefox Full support 11 Full support 11 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 10	Opera Full support 12.1	Safari Full support 5	WebView Android Full support ≤37	Chrome Android Full support 18	Firefox 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 12.1	Safari iOS Full support 4.2	Samsung Internet Android Full support 1.0
WebSocket() constructor	Chrome Full support Yes	Edge Full support ≤79	Firefox Full support 7 Full support 7 No support 4 — 7 Notes' Notes' Parameter protocols not supported.	IE ?	Opera Full support Yes	Safari ?	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 7	Opera Android ?	Safari iOS ?	Samsung Internet Android Full support Yes
binaryType	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
bufferedAmount	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
close	Chrome Full support 4	Edge Full support 12	Firefox Full support 8 Full support 8 No support 4 — 8 Notes' Notes' Parameters not supported, see bug 674716.	IE Full support 10	Opera Full support 12.1	Safari Full support 5	WebView Android Full support ≤37	Chrome Android Full support 18	Firefox Android Full support 8 Full support 8 No support 4 — 8 Notes' Notes' Parameters not supported, see bug 674716.	Opera Android Full support 12.1	Safari iOS Full support 4.2	Samsung Internet Android Full support 1.0
close event	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari ?	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android ?	Safari iOS ?	Samsung Internet Android Full support Yes
error event	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari ?	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android ?	Safari iOS ?	Samsung Internet Android Full support Yes
extensions	Chrome Full support Yes	Edge Full support 12	Firefox Full support 8	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 8	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
message event	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari ?	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android ?	Safari iOS ?	Samsung Internet Android Full support Yes
onclose	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
onerror	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
onmessage	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
onopen	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
open event	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari ?	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android ?	Safari iOS ?	Samsung Internet Android Full support Yes
protocol	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
Supports protocol as specified by RFC 6455	Chrome Full support 16	Edge Full support 12	Firefox Full support 11	IE Full support 10	Opera Full support 15	Safari Full support 6	WebView Android Full support Yes	Chrome Android Full support 18	Firefox Android Full support 14	Opera Android Full support 14	Safari iOS Full support 6	Samsung Internet Android Full support 1.0
readyState	Chrome Full support 43	Edge Full support 12	Firefox Full support 19	IE Full support 10	Opera Full support 30	Safari Full support 10	WebView Android Full support 43	Chrome Android Full support 43	Firefox Android Full support 19	Opera Android Full support 30	Safari iOS Full support 10	Samsung Internet Android Full support 4.0
send	Chrome Full support 4	Edge Full support 12	Firefox 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 10	Opera Full support 12.1	Safari Full support 5	WebView Android Full support ≤37	Chrome Android Full support 18	Firefox 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 12.1	Safari iOS Full support 4.2	Samsung Internet Android Full support 1.0
url	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE ?	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
Available in workers	Chrome Full support Yes	Edge Full support ≤18	Firefox Full support 37	IE ?	Opera ?	Safari ?	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 37	Opera 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

• Writing WebSocket client applications

WebSocket by Mozilla Contributors is licensed under CC-BY-SA 2.5.