HTTP 400 Bad Request

The server cannot process the request because its syntax or input is invalid.

Use 400 for malformed JSON, invalid query syntax, or an otherwise structurally invalid request.

httpstatus codeclient errorvalidation

Response (http)

HTTP/1.1 400 Bad Request

Use 400 for malformed JSON, invalid query syntax, or an otherwise structurally invalid request.

Common mistakes

Using 400 as a catch-all for well-formed requests that fail business rules; use 422 or 409 for those.

Registry reference: RFC9110, Section 15.5.1

Sources