HTTP 505 HTTP Version Not Supported
The server does not support the HTTP protocol version used in the request.
5xx Server Error
505
HTTP Version Not Supported
Description
The 505 HTTP Version Not Supported status code indicates that the server does not support, or refuses to support, the major version of HTTP that was used in the request message. The server is indicating that it is unable or unwilling to complete the request using the same major version as the client. The server should generate a representation for the 505 response that describes why that version is not supported and what other protocols are supported by that server. This is a rare status code in practice, as most modern servers support HTTP/1.0, HTTP/1.1, and HTTP/2.
When Is It Used?
Returned when a server receives a request using an HTTP version it does not support. For example, a server that only supports HTTP/1.1 receiving a request using HTTP/3, or a legacy server that does not support HTTP/2.
Example Response
HTTP/1.1 505 HTTP Version Not Supported
Content-Type: text/plain
This server only supports HTTP/1.1 and HTTP/2.