422 Unprocessable Content means the server understands the content type and the request syntax is correct, but it cannot process the instructions it contains. For example, a JSON body parses fine, but an email field is invalid or a required value is out of range.
WebDAV (RFC 4918) introduced the code as "Unprocessable Entity", and RFC 9110 adopted it into core HTTP under its new name. Many web frameworks and APIs, such as Ruby on Rails and Laravel, use it for validation errors and return field-level messages in the body.
Use 400 and 422 consistently: 400 for requests that cannot be parsed, 422 for requests that parse but fail validation.
Example response
HTTP/1.1 422 Unprocessable Content
Date: Fri, 06 Nov 2026 10:15:32 GMT
Content-Type: application/json
Content-Length: 77
{"message":"Validation failed","errors":[{"field":"email","code":"invalid"}]}SEO and redirect checking
422 is a code for APIs and form processing. Crawlers use GET and should not see it; a page that returns 422 to GET is treated as a 4xx error and not indexed.
Common causes and use cases
- A form submission or API call fails validation: a missing field, an invalid email address or a username that is taken.
- A document is valid JSON but does not match the API's schema.
- A WebDAV
PROPPATCHorLOCKbody is well-formed XML but semantically wrong.