5×× Server Error

503 Service Unavailable

The server is currently unable to handle the request due to a temporary overload or scheduled maintenance, which will likely be alleviated after some delay.

The server MAY send a Retry-After header field¹ to suggest an appropriate amount of time for the client to wait before retrying the request.

Note: The existence of the 503 status code does not imply that a server has to use it when becoming overloaded. Some servers might simply refuse the connection.

• ¹ Retry-After RFC7231 Section 7.1.3
• Source: RFC7231 Section 6.6.4

503 Code References

.NET HTTP Status Enum HttpStatusCode.ServiceUnavailable

Rust HTTP Status Constant http::StatusCode::SERVICE_UNAVAILABLE

Rails HTTP Status Symbol :service_unavailable

Go HTTP Status Constant http.StatusServiceUnavailable

Symfony HTTP Status Constant Response::HTTP_SERVICE_UNAVAILABLE

Python2 HTTP Status Constant httplib.SERVICE_UNAVAILABLE

Python3+ HTTP Status Constant http.client.SERVICE_UNAVAILABLE

Python3.5+ HTTP Status Constant http.HTTPStatus.SERVICE_UNAVAILABLE