HTTP 506 Variant Also Negotiates

When is 506 used?

• Content negotiation loop detection

How to handle a 506 response

The problem is on the server side. Check server and proxy logs, retry idempotent requests with exponential backoff, and alert on sustained 5xx rates.

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 506 from your server

Node.js (Express)

res.status(506).json({ message: 'Variant Also Negotiates' });

Python (Flask)

return {"message": "Variant Also Negotiates"}, 506

Go (net/http)

w.WriteHeader(506)