// http 4xx · client error
HTTP 409 Conflict
The request conflicts with the current state of the resource.
What HTTP 409 Conflict means
409 Conflict means the request couldn't be completed because it conflicts with the current state of the resource — a classic example is a version/edit conflict or trying to create something that already exists.
Which category is it?
409 is a 4xx code — Client error. 4xx means the request has a problem the client must fix — bad syntax, missing authentication, or a resource that isn't there. It's the caller's responsibility.
Common causes
- Editing a resource that changed since you fetched it
- Creating a resource with a duplicate unique key
- Concurrent updates to the same record
How to fix it
- Re-fetch the latest state and reapply the change
- Use optimistic concurrency (ETags/versions)
- Handle duplicates before creating