Front desk · HTTP Status Codes
5×× Server Error
505 HTTP Version Not Supported
· filed 2026-07-18 · click a code to copy
HTTP 505 HTTP Version Not Supported is a server error-class status code defined in RFC9110. The HTTP protocol version used in the request is not supported.
Server-error responses admit the fault is on the server's side: the request was valid, but the server failed to fulfil it. On the wire, the response begins with the status line HTTP/1.1 505 HTTP Version Not Supported.