4xx Client Errors
HTTP 406 Not Acceptable
The resource cannot generate content matching the Accept headers sent by the client.
When is 406 used?
- Client only accepts XML but server returns JSON
- Content negotiation failure
How to handle a 406 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.comHow to return 406 from your server
Node.js (Express)
res.status(406).json({ message: 'Not Acceptable' });Python (Flask)
return {"message": "Not Acceptable"}, 406Go (net/http)
w.WriteHeader(406)Frequently Asked Questions
What does HTTP 406 mean?
406 Not Acceptable: The resource cannot generate content matching the Accept headers sent by the client.
Is 406 an error?
Yes. 406 is in the 4xx Client Errors class. Client errors: the request is malformed, unauthorized, or targets something that does not exist.