CloseEvent: code property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The code read-only property of the CloseEvent interface returns a WebSocket connection close code indicating the reason the server gave for closing the connection.

Value

An integer WebSocket connection close code in the range 1000 - 4999, indicating the reason the server gave for closing the connection.

Status code Meaning Description
0–999 Not used.
1000 Normal Closure The connection successfully completed the purpose for which it was created.
1001 Going Away The endpoint is going away, either because of a server failure or because the browser is navigating away from the page that opened the connection.
1002 Protocol error The endpoint is terminating the connection due to a protocol error.
1003 Unsupported Data The connection is being terminated because the endpoint received data of a type it cannot accept. (For example, a text-only endpoint received binary data.)
1004 Reserved Reserved. A meaning might be defined in the future.
1005 No Status Rcvd Reserved. Indicates that no status code was provided even though one was expected.
1006 Abnormal Closure Reserved. Indicates that a connection was closed abnormally (that is, with no close frame being sent) when a status code is expected.
1007 Invalid frame payload data The endpoint is terminating the connection because a message was received that contained inconsistent data (e.g., non-UTF-8 data within a text message).
1008 Policy Violation The endpoint is terminating the connection because it received a message that violates its policy. This is a generic status code, used when codes 1003 and 1009 are not suitable.
1009 Message Too Big The endpoint is terminating the connection because a data frame was received that is too large.
1010 Mandatory Ext. The client is terminating the connection because it expected the server to negotiate one or more extension, but the server didn't.
1011 Internal Error The server is terminating the connection because it encountered an unexpected condition that prevented it from fulfilling the request.
1012 Service Restart The server is terminating the connection because it is restarting.
1013 Try Again Later The server is terminating the connection due to a temporary condition, e.g. it is overloaded and is casting off some of its clients.
1014 Bad Gateway The server was acting as a gateway or proxy and received an invalid response from the upstream server. This is similar to 502 HTTP Status Code.
1015 TLS handshake Reserved. Indicates that the connection was closed due to a failure to perform a TLS handshake (e.g., the server certificate can't be verified).
1016–2999 For definition by future revisions of the WebSocket Protocol specification, and for definition by extension specifications.
3000–3999 For use by libraries, frameworks, and applications. These status codes are registered directly with IANA. The interpretation of these codes is undefined by the WebSocket protocol.
4000–4999 For private use, and thus can't be registered. Such codes can be used by prior agreements between WebSocket applications. The interpretation of these codes is undefined by the WebSocket protocol.

Examples

The following example prints the value of code to the console.

js
WebSocket.onclose = (event) => {
  console.log(event.code);
};

Specifications

Specification
WebSockets Standard
# ref-for-dom-closeevent-code②

Browser compatibility

BCD tables only load in the browser

See also