A CloseEvent is sent to clients using WebSockets when the connection is closed. This is delivered to the listener indicated by the WebSocket object's onclose attribute.


Creates a new CloseEvent.


This interface also inherits properties from its parent, Event.

CloseEvent.code Read only
Returns an unsigned short containing the close code send by the server. The following values are permitted status codes.
Status code Name Description
0999   Reserved and not used.
1000 CLOSE_NORMAL Normal closure; the connection successfully completed whatever purpose for which it was created.
1001 CLOSE_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 CLOSE_PROTOCOL_ERROR The endpoint is terminating the connection due to a protocol error.
1003 CLOSE_UNSUPPORTED 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. A meaning might be defined in the future.
1005 CLOSE_NO_STATUS Reserved.  Indicates that no status code was provided even though one was expected.
1006 CLOSE_ABNORMAL Reserved. Used to indicate that a connection was closed abnormally (that is, with no close frame being sent) when a status code is expected.
1007   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   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 CLOSE_TOO_LARGE The endpoint is terminating the connection because a data frame was received that is too large.
1010   The client is terminating the connection because it expected the server to negotiate one or more extension, but the server didn't.
1011   The server is terminating the connection because it encountered an unexpected condition that prevented it from fulfilling the request.
10121014   Reserved for future use by the WebSocket standard.
1015   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).
10161999   Reserved for future use by the WebSocket standard.
20002999   Reserved for use by WebSocket extensions.
30003999   Available for use by libraries and frameworks. May not be used by applications.
40004999   Available for use by applications.
CloseEvent.reason Read only
Returns a DOMString indicating the reason the server closed the connection. This is specific to the particular server and sub-protocol.
CloseEvent.wasClean Read only
Returns a Boolean that Indicates whether or not the connection was cleanly closed.


This interface also inherits methods from its parent, Event.

Initializes the value of a CloseEvent created. If the event has already being dispatched, this method does nothing.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support ? 8.0 (8.0) [1][2] ? ? ?
initCloseEvent() Not supported 8.0 (8.0)
Removed in 41 (41)
Not supported Not supported Not supported
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? 8.0 (8.0) ? ? ?
initCloseEvent() Not supported 8.0 (8.0)
Removed in 41.0 (41)
Not supported Not supported Not supported

[1] Prior to Gecko 8.0 (Firefox 8.0 / Thunderbird 8.0 / SeaMonkey 2.5), Gecko sent the WebSocket close event to the listener as a simple event. Support for CloseEvent was implemented in Gecko 8.0.

[2] Prior to Gecko 12.0 (Firefox 12.0 / Thunderbird 12.0 / SeaMonkey 2.9), Gecko reported the close code CLOSE_NORMAL when the channel was closed due to an unexpected error, or if it was closed due to an error condition that the specification doesn't cover. Now CLOSE_GOING_AWAY is reported instead.

See also


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Last updated by: Sebastianz,