409 Conflict means the request could not be completed because it conflicts with the current state of the target resource. The client may be able to resolve the conflict and send the request again, so the response should contain enough information to identify the source of the conflict.
It is most common with PUT and PATCH: two users edit the same document, a client uploads a version older than the one stored, or an API refuses to create a record that already exists. In WebDAV, MKCOL and PUT return 409 when the parent collection does not exist.
For conditional requests with If-Match, the standard response is 412 Precondition Failed; 409 covers conflicts that the server detects by itself.
Example response
HTTP/1.1 409 Conflict
Date: Fri, 06 Nov 2026 10:15:32 GMT
Content-Type: application/problem+json
Content-Length: 99
{"title":"Edit conflict","detail":"The document was changed by another user (current version: 7)."}SEO and redirect checking
409 belongs to APIs and editing workflows. Crawlers fetch pages with GET, so a public page should never return 409; if it does, it is treated as a 4xx error and not indexed.
Common causes and use cases
- Two users saved the same record, and the second save is rejected.
- A client tries to create a user, file or other resource that already exists.
- A client uploads a file version that is older than the current one.
- A WebDAV
MKCOLorPUTtargets a folder whose parent does not exist.