WebSocket Close Codes

Normal Closure

1000 Normal Closure indicates the WebSocket connection was closed cleanly and intentionally by either endpoint.

Going Away

1001 Going Away indicates the endpoint is 'going away' – a server is shutting down or restarting, or a browser tab is being closed.

Protocol Error

1002 Protocol Error indicates the endpoint is terminating the connection because the peer violated the WebSocket protocol.

Unsupported Data

1003 Unsupported Data is sent when an endpoint receives a data type it cannot handle – typically a binary message when only text is supported, or vice versa.

No Status Received

1005 No Status Received is a reserved code used internally by WebSocket libraries to indicate the TCP connection was closed without a WebSocket close frame.

Abnormal Closure

1006 Abnormal Closure is a reserved code used by WebSocket libraries when the connection was closed abnormally – without a close handshake and without a specific error code.

Invalid Frame Payload Data

1007 Invalid Frame Payload Data is sent when a text message frame contains data that is not valid UTF-8.

Policy Violation

1008 Policy Violation is a generic close code for when an endpoint receives a message that violates its policies – authorization failure, rate limiting, content policy enforcement, or a custom application rule.

Message Too Big

1009 Message Too Big is sent when an endpoint receives a message that exceeds the maximum message size it is configured to accept.

Internal Server Error

1011 Internal Server Error is sent by a server when an unexpected condition prevented it from processing a client request.

Service Restart

1012 Service Restart is sent when a server is restarting for a non-error reason – planned restart, deployment, or maintenance.

Try Again Later

1013 Try Again Later is sent when the server is temporarily unable to accept new connections due to overload or temporary unavailability.

Bad Gateway

1014 Bad Gateway is sent when a server acting as a gateway or proxy receives an invalid response from an upstream WebSocket server.

TLS Handshake Failure

1015 TLS Handshake Failure is a reserved code that indicates the WebSocket connection was closed because the TLS (wss://) handshake failed.