HTTP 409 Conflict means the request could not be completed because it conflicts with the current state of the target resource. This is most common with PUT requests where the client is trying to update a resource that has been modified by another client.
Status
409 ConflictExample
POST /wiki/edit/dns-article HTTP/1.1
Host: www.example.com
User-Agent: curl/8.6.0
Content-Type: application/x-www-form-urlencoded
Content-Length: 62
title=DNS+Guide&content=Updated+text&base_revision=42HTTP/1.1 409 Conflict
Content-Type: text/html; charset=utf-8
Content-Length: 220
<!doctype html>
<html lang="en">
<head>
<title>409 Conflict</title>
</head>
<body>
<h1>Edit Conflict</h1>
<p>Someone else edited this page while you were working. Please review their changes and try again.</p>
</body>
</html>How to Troubleshoot
Read the current resource state
Fetch the latest version of the resource and resolve any conflicts before retrying.
Use conditional requests
Include If-Match or If-Unmodified-Since headers to prevent conflicts.
curl -X PUT -H 'If-Match: "etag-value"' -d '{"data":"new"}' https://api.example.com/resourceCheck response body for conflict details
The 409 response body typically explains what the conflict is and how to resolve it.
Common Causes
Concurrent modification conflict
highTwo clients are trying to update the same resource simultaneously, and the server detects a conflict.
Duplicate resource creation
highThe client is trying to create a resource that already exists with a conflicting unique constraint.
Related Status Codes
References
| Specification | Section |
|---|---|
| HTTP Semantics | RFC 9110 §15.5.10 |
Frequently Asked Questions
This reference was compiled from official RFCs, protocol specifications, and hands-on troubleshooting experience. AI tools were used primarily for formatting and organizing the content on the page.