What is HTTP 422 Unprocessable Entity?

 The HTTP 422 status code, known as "Unprocessable Entity," is a client error status indicating that the server understands the content type of the request entity and the syntax of the request entity is correct, but it was unable to process the contained instructions. This status code is typically encountered when the server is unable to follow the request due to semantic errors.

For instance, in the context of web applications and APIs, an HTTP 422 status might be returned when the request payload is syntactically valid but semantically incorrect. This can occur when fields in the request body contain invalid data or violate business logic rules. For example, submitting a form with a properly formatted date field but with a date that doesn't exist (like February 30th) could trigger a 422 response.

Unlike a 400 Bad Request status, which is used when the server cannot understand the request due to malformed syntax, a 422 status indicates that the server has understood the request but cannot process it due to logical errors in the content. It is important for developers to handle this status correctly to ensure that their applications can gracefully manage validation errors and provide meaningful feedback to the user.

Understanding HTTP 422 is crucial for building robust APIs and web applications that can handle data validation effectively. By properly utilizing this status code, developers can improve the user experience by providing precise error messages and guiding users towards correcting their input, thereby enhancing the overall reliability and usability of the application.