---
title: "406 Not Acceptable — what it means and how to fix it"
description: "The server cannot produce a response in any of the formats the client said it would accept. What causes an HTTP 406, what to try as a visitor, and what to check if it is your own site."
url: https://atoneplace.net/error/406/
site: "At One Place"
---

# HTTP 406 — Not Acceptable

**HTTP 406: Not Acceptable**

The server cannot produce a response in any of the formats the client said it would accept.

## What 406 actually means

Content negotiation failed. The client sent `Accept`, `Accept-Language` or `Accept-Encoding` headers restricting what it will take, and the server has nothing matching. In real life this is far more often a misconfigured security module than genuine negotiation failure — mod_security and several hosting stacks return 406 when a request trips a rule, which sends people hunting for a content-type problem that does not exist.

## Common causes

- An `Accept` header requesting a format the endpoint does not produce
- A mod_security or WAF rule rejecting the request and reporting it as 406
- An API strictly enforcing `Accept: application/json` against a client sending something else
- A missing or wrong `Accept-Encoding` negotiation on a server that only serves compressed content

## If you're just trying to view the page

1. Try a different browser — a plugin or a modified `Accept` header can trigger this
2. Disable browser extensions that alter request headers, and any VPN or proxy that rewrites traffic
3. If it happens on one shared host and not others, it is likely a server-side security rule rather than anything about your setup

## If it's your site

1. Check mod_security logs first; on shared hosting this is the cause more often than negotiation is
2. Consider ignoring an unsatisfiable `Accept` and serving your default representation, which the specification permits
3. If you do return 406, list the available media types in the body so the client can retry sensibly

## Reference

- **Status code:** 406
- **Reason phrase:** Not Acceptable
- **Category:** 4xx — Client Error
- **Defined in:** RFC 9110 §15.5.7

## Common questions

### What does HTTP 406 mean?

The server cannot produce a response in any of the formats the client said it would accept. Content negotiation failed. The client sent `Accept`, `Accept-Language` or `Accept-Encoding` headers restricting what it will take, and the server has nothing matching.

### How do I fix a 406 error?

Try a different browser — a plugin or a modified `Accept` header can trigger this

### Is 406 a client error or a server error?

406 is in the 4xx range, which means client error. The request itself was the problem, so retrying it unchanged will usually return the same code.

## Related pages

- [404 Not Found](https://atoneplace.net/error/404/)
- [403 Forbidden](https://atoneplace.net/error/403/)
- [401 Unauthorized](https://atoneplace.net/error/401/)
- [429 Too Many Requests](https://atoneplace.net/error/429/)
- [400 Bad Request](https://atoneplace.net/error/400/)
- [413 Content Too Large](https://atoneplace.net/error/413/)
- [422 Unprocessable Content](https://atoneplace.net/error/422/)
- [405 Method Not Allowed](https://atoneplace.net/error/405/)
- [409 Conflict](https://atoneplace.net/error/409/)
- [415 Unsupported Media Type](https://atoneplace.net/error/415/)
- [408 Request Timeout](https://atoneplace.net/error/408/)
- [410 Gone](https://atoneplace.net/error/410/)

## Sources

- Hypertext Transfer Protocol (HTTP) Status Code Registry — IANA (https://www.iana.org/assignments/http-status-codes/)
- RFC 9110: HTTP Semantics — IETF (https://www.rfc-editor.org/rfc/rfc9110.html)