406 Not Acceptable

What it means

Content negotiation failed: the client asked for a format or language the server cannot provide.

Common causes

• An Accept header requests an unsupported format.
• Some security modules return 406 for blocked requests.

How to fix it

1. Send a broader Accept header such as */*.
2. Review server security module logs.

Example response

HTTP/1.1 406 Not Acceptable
Content-Type: text/plain; charset=utf-8

Worked example

A client sends a request the server cannot fulfill as submitted. Check the response body and request details, correct the input or permissions, and retry only after the relevant issue is resolved.

How to read this response

1. Find the status line in your browser's Network panel, API client, or server access log.
2. Read the response body and headers shown above; headers such as Location, Allow, Retry-After, and WWW-Authenticate explain the next step.
3. Use the code's class to orient your diagnosis: informational, successful, redirected, request-related, or server-side.

How to check a status code

Enter a URL in the HTTP Status Checker to see its status code, every redirect hop, and response time. For redirect-heavy pages, the Website Speed Test shows how much time redirects add.

Frequently asked questions

What it means: HTTP 406

406 Not Acceptable: The server cannot produce a response matching the client's Accept headers.

Common causes: 406

An Accept header requests an unsupported format. Some security modules return 406 for blocked requests.

How to fix it: HTTP 406

Send a broader Accept header such as */*. Review server security module logs.

Tools