Front desk · HTTP Status Codes
4×× Client Error
400 Bad Request
· filed 2026-07-18 · click a code to copy
HTTP 400 Bad Request is a client error-class status code defined in RFC9110. The server cannot process the request due to a client error such as malformed syntax.
Client-error responses signal that the problem is on the requesting side: the request is malformed, unauthorized, or aimed at something that isn't there. On the wire, the response begins with the status line HTTP/1.1 400 Bad Request.