422 Unprocessable Entity

A 422 Unprocessable Entity error means the server understands the request format and syntax, but cannot process the contained instructions due to semantic errors. Unlike a 400, the request is well-formed, but the data fails business logic validation. For developers, this is commonly returned when form input or API payload values are invalid, such as an email field containing a non-email string.

Common causes

• Form or API field values fail server-side validation rules, such as invalid email format or out-of-range numbers
• Required business logic constraints are not met, such as insufficient account balance for a transaction
• Data types are correct but values are semantically invalid, like a start date after an end date
• Referencing a related resource that does not exist or is in an incompatible state
• Submitting an entity that violates unique constraints at the application logic level

How to fix it

• Read the response body carefully as it typically contains specific field-level validation error messages
• Add client-side validation that mirrors server-side rules to catch errors before submission
• Ensure all referenced related resources exist and are in a valid state before submitting
• Verify that field values meet business logic requirements such as ranges, formats, and dependencies
• Log the full response body in development to quickly identify which validation rule failed

Related HTTP errors