# 422 Unprocessable Content

> The request body was syntactically correct but failed semantic business rules validation.

Source: https://apiguide.dev/status-codes/422
Class: client-error
Defined in: RFC 9110, Section 15.5.21 <https://www.rfc-editor.org/rfc/rfc9110.html#section-15.5.21>
Updated: 2026-10-14

## What does HTTP status code 422 mean?

The 422 Unprocessable Content status code (titled "Unprocessable Entity" before RFC 9110) indicates that the server understands the content type and syntax of the request, but cannot process the contained instructions due to semantic validation failures.

## When to use it in APIs

The primary status code for input validation failures. Use 422 when required fields are missing, strings fail regex constraints, or numbers fall out of range.

## How it compares to other codes

* **400 Bad Request**: Use 400 when the JSON is malformed and cannot be parsed. Use 422 when the JSON parses successfully but has validation errors.