ErrorFindly
4094xx Client ErrorMedium

HTTP 409 Conflict

Defined in RFC 7231

What Does HTTP 409 Mean?

The request conflicts with the current state of the server, such as an edit conflict or duplicate resource creation.

Common Causes

  1. 1Attempting to create a resource that already exists
  2. 2Edit conflict due to concurrent modifications
  3. 3Version mismatch in optimistic locking
  4. 4Duplicate entry violation

Impact

  • ⚠Cannot save changes due to conflict
  • ⚠Duplicate submission detected
  • ⚠Need to refresh and retry

Developer Fix

For web developers and application engineers

  1. 1Implement optimistic concurrency control with ETags
  2. 2Handle conflicts by showing diff to the user
  3. 3Use unique constraint checks before creation
  4. 4Implement merge strategies for concurrent edits

Server Admin Fix

For system administrators and DevOps engineers

  1. 1Monitor for frequent conflict patterns
  2. 2Implement proper locking mechanisms
  3. 3Optimize database unique constraints

Frequently Asked Questions

When should I return a 409 Conflict?
Use 409 when the request can't be completed because it conflicts with the resource's current state — such as duplicate creation, edit conflicts, or state machine violations.
How do I resolve a 409 Conflict?
Fetch the current resource state, compare it with your changes, resolve any differences, and retry the request. The response body should describe the conflict.

Related HTTP Status Codes

412Precondition Failed422Unprocessable Entity423Locked

About the Author

Web Infrastructure Team

Verified against official RFC specifications and real-world server configurations. HTTP status code behavior confirmed across Apache, Nginx, and Cloudflare.