HTTP 406 — Not Acceptable
4xx Client Error
What it means
The server cannot produce a response matching the client's Accept header.
What to do about it
Relax the Accept header, or add the requested representation on the server. Rare in practice — most servers ignore the header and return their default.
Where it sits
406 belongs to the 4xx family: The request contains something the server will not or cannot process. The fix is normally on the client side.
HTTP/1.1 406 Not AcceptableChecking it yourself
# see the status code and headers only
curl -sI https://example.com/path
# follow redirects and print each hop
curl -sIL -o /dev/null -w "%{http_code} %{url_effective}\n" https://example.com/path
# JavaScript
const r = await fetch(url);
console.log(r.status, r.statusText);How this code behaves
| Cacheable by default | No — caches must not store this response unless explicit cache headers permit it. |
| Safe to retry | No. Retrying an identical request will produce the same result — the request itself must change. |
| Effect on search indexing | No direct effect. |
Returning 406 correctly
# nginx
return 406;
# Express
res.status(406).json({ error: 'Not Acceptable' });
# Go
w.WriteHeader(406)
# Python (Flask)
return jsonify(error='Not Acceptable'), 406;Frequently asked questions
What does HTTP 406 mean?
The server cannot produce a response matching the client's Accept header.
How do I fix a 406 error?
Relax the Accept header, or add the requested representation on the server. Rare in practice — most servers ignore the header and return their default.
Is 406 a client or server problem?
A client problem by definition — the request needs to change. That said, a 4xx can still be the server’s fault if it is misconfigured and rejecting valid requests.