HTTP 409 Conflict

When is 409 used?

• Concurrent editing conflicts
• Creating a resource that already exists
• Version control merge conflicts

How to handle a 409 response

Inspect the request — URL, method, headers, credentials, and body. Retrying the same request unchanged will usually fail again; 429 is the exception, where you should wait for the Retry-After period.

Check the status code a URL returns from the command line:

curl -s -o /dev/null -w "%{http_code}\n" https://example.com

How to return 409 from your server

Node.js (Express)

res.status(409).json({ message: 'Conflict' });

Python (Flask)

return {"message": "Conflict"}, 409

Go (net/http)

w.WriteHeader(409)