HTTP 406 Not Acceptable

What does HTTP 406 mean?

The server cannot produce a response matching the client’s Accept headers. Content negotiation failed: the client asked for, say, application/xml only, and the server can only produce JSON. Some security modules (mod_security) also misuse 406 to block requests.

4xx Client error: The request has a problem the client can fix: wrong URL, missing credentials, bad data or too many requests.

Common causes of a 406 error

• Strict Accept header from an API client.
• A web application firewall rule.

How to fix 406 Not Acceptable

• Send Accept: */* or a supported type.
• Check WAF logs if browsers get 406.

406 and SEO

Rare for web pages; if Googlebot receives 406 the page is not indexed.

Example response

HTTP/1.1 406 Not Acceptable

How to return a 406 response

Node.js (Express)

res.status(406).json({ error: 'Not Acceptable' });

PHP

http_response_code(406);

Python (Flask)

return {'error': 'Not Acceptable'}, 406

Go (net/http)

w.WriteHeader(406)

nginx

return 406;

Related status codes

• 415 Unsupported Media Type — The server does not support the format of the request body.
• 400 Bad Request — The server cannot process the request because it is malformed.

Check which status code a URL returns with the HTTP header checker.