HTTP 406 Not Acceptable means the server cannot generate a response matching the criteria given by the client's Accept, Accept-Language, Accept-Encoding, or Accept-Charset headers. The server can only return content in formats not listed in the request.
Status
406 Not AcceptableExample
Request
GET /docs/guide.pdf HTTP/1.1
Host: www.example.com
User-Agent: curl/8.6.0
Accept: application/mswordResponse
HTTP/1.1 406 Not Acceptable
Content-Type: text/html; charset=utf-8
Content-Length: 200
<!doctype html>
<html lang="en">
<head>
<title>406 Not Acceptable</title>
</head>
<body>
<h1>Not Acceptable</h1>
<p>The server cannot serve this content in the format your client requested.</p>
</body>
</html>How to Troubleshoot
1
Broaden the Accept header
Use a less restrictive Accept header or include multiple acceptable types.
curl -H 'Accept: application/json, text/html, */*' https://api.example.com/resource
2
Check available content types
Consult the API documentation to find which content types the server can return.
Common Causes
Restrictive Accept header
highThe client requested a content type the server does not support (e.g., Accept: application/xml when only JSON is available).
Related Status Codes
References
| Specification | Section |
|---|---|
| HTTP Semantics | RFC 9110 §15.5.7 |
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.