409 Conflict
The request conflicts with the current state of the resource.
| Class | Client error (4xx) |
|---|---|
| Defined in | RFC9110, Section 15.5.10 |
| Cacheable by default | No, unless explicit freshness headers allow it |
Common causes
- Creating a resource that already exists, such as a duplicate username.
- An edit based on an outdated version of a resource.
What to do
Reload the current state, resolve the conflict and retry. Include enough detail in the response for the client to resolve it.
Related codes
- 412 Precondition Failed: A precondition in the request headers, such as If-Match, evaluated to false.
- 422 Unprocessable Content: The server understands the content type and syntax but cannot process the contained instructions.
- 400 Bad Request: The server cannot process the request because it looks malformed.