4xx Client Error
422 Unprocessable Content
The syntax is fine and the content type is understood, but the data itself fails validation.
What causes it
- A valid JSON body with a semantically invalid field — an email without an @, an end date before the start date.
- Rails, Laravel and FastAPI use 422 as the default validation-error status.
How to fix it
- Return a per-field error map in the body. A bare 422 with no detail is the least useful response an API can give.
- If the body was not parseable at all, 400 is the more accurate status.
At a glance
- Class
- 4xx Client Error
- Reference
- RFC 9110 §15.5.21
- Standardised
- Yes
- Retry the request?
- No — fix the request
Other 4xx client error codes
- 400 Bad Request
- 401 Unauthorized
- 402 Payment Required
- 403 Forbidden
- 404 Not Found
- 405 Method Not Allowed
- 406 Not Acceptable
- 407 Proxy Authentication Required
- 408 Request Timeout
- 409 Conflict
- 410 Gone
- 411 Length Required
- 412 Precondition Failed
- 413 Content Too Large
- 414 URI Too Long
- 415 Unsupported Media Type
- 416 Range Not Satisfiable
- 417 Expectation Failed
- 418 I'm a teapot
- 421 Misdirected Request
- 423 Locked
- 424 Failed Dependency
- 425 Too Early
- 426 Upgrade Required
- 428 Precondition Required
- 429 Too Many Requests
- 431 Request Header Fields Too Large
- 451 Unavailable For Legal Reasons
- 499 Client Closed Request