HTTP 409 Conflict vs 422 Unprocessable Content
Both HTTP 409 (Conflict) and 422 (Unprocessable Content) belong to the 4xx Client Error category. 409 indicates that the request conflicts with the current state of the server. Often due to concurrent modification or business rule violations. Meanwhile, 422 means that the server understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors.
Description
The request conflicts with the current state of the server. Often due to concurrent modification or business rule violations.
When You See It
When trying to create a resource that already exists, or updating a resource that was modified by another request.
How to Fix
Refresh the resource state, resolve conflicts, and retry. Use ETags for optimistic concurrency.
Description
The server understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors.
When You See It
When form validation fails — correct syntax but invalid data (e.g., email format wrong, date in the past).
How to Fix
Check the response body for specific validation errors and correct the input data.
Key Differences
HTTP 409: The request conflicts with the current state of the server. Often due to concurrent modification or business rule violations.
HTTP 422: The server understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors.
You encounter 409 when when trying to create a resource that already exists, or updating a resource that was modified by another request.
You encounter 422 when when form validation fails — correct syntax but invalid data (e.g., email format wrong, date in the past).
When to Use Which
For 409 (Conflict): Refresh the resource state, resolve conflicts, and retry. Use ETags for optimistic concurrency. For 422 (Unprocessable Content): Check the response body for specific validation errors and correct the input data.