What causes a 506 error?
A content negotiation setup where the selected variant is itself negotiable, so the server cannot settle on a concrete representation. It is a server misconfiguration.
HTTP 506 VARIANT ALSO NEGOTIATES
A content-negotiation configuration error: the chosen variant negotiates too. 506 belongs to the 5xx server error class and is defined in RFC 2295.
Loading the workbench.
About HTTP 506
What Does HTTP 506 Variant Also Negotiates Mean?
A content-negotiation configuration error: the chosen variant negotiates too. The code is registered with IANA and defined in RFC 2295.
Server error: the server failed to fulfill a valid request. Every code from 500 to 599 shares that general meaning, so a client that does not recognise 506 must treat it like 500.
When Do You See a 506 Response?
506 Variant Also Negotiates is a configuration error in transparent content negotiation (RFC 2295). The server was set up so that the variant chosen for a request is itself a negotiable resource, creating a loop instead of an actual representation. In practice it appears only with Apache's mod_negotiation and type-map files that point at each other. Ordinary applications almost never produce it.
How Do You Fix a 506?
This is a server-side problem; clients cannot fix it. Administrators should check content negotiation settings, such as Apache type-map files and MultiViews, and make sure each variant points at a concrete file rather than another negotiable resource. Disabling transparent negotiation and selecting variants with ordinary Accept-based logic usually resolves it. Check the server error log, which normally names the resource where the negotiation loop occurred.
What Does a 506 Response Look Like?
HTTP/1.1 506 Variant Also Negotiates
Content-Type: text/html506 is not cacheable by default: a browser or CDN stores it only when Cache-Control or Expires explicitly allows it.
To inspect a real one without sending it anywhere:
- Copy the response headers from your browser Network tab, or from
curl -i. - Paste them into the Header decoder to see every header explained.
- Check caching in the Cache lane.
Which Status Codes Are Related to 506?
- 300 Multiple Choices: Several representations are available and the client may choose.
- 406 Not Acceptable: No representation matches the Accept headers the client sent.
- 500 Internal Server Error: A generic server failure, usually an unhandled exception.
Browse every code on the HTTP status codes page.
What Other Lanes Are in the Reference Section?
- HTTP status codes: Every IANA-registered status code, with a page per code.
- MIME types: File extensions to Content-Type, searchable both ways, plus a Content-Type parser.
- HTTP methods: GET, POST, PUT, PATCH, DELETE and the rest: safe, idempotent, cacheable.
Elsewhere in 2http: Header decoder, Cookie decoder, Cache-Control decoder, CORS checker, User-agent parser, and all eleven lanes on the 2http home page. Part of the 2suite.io privacy-first ecosystem.
Frequently Asked Questions
Will I ever see 506 on a modern website?
Very rarely. It requires transparent content negotiation, a little-used feature mostly found in older Apache configurations. Most modern frameworks choose a representation directly and never produce it.
Is HTTP 506 an error?
Yes. 506 is a server error response: the server failed to handle a valid request, so retrying later may work.
Is a 506 response cacheable by default?
No. Caches store a 506 only when Cache-Control or Expires explicitly allows it.
How Can You Verify That Nothing Leaves This Browser?
You do not have to take our word that your headers stay here. Developer tools show every request a page makes, so you can watch this page work and confirm that nothing is sent. The check takes under a minute.
- Open your browser developer tools with
F12, orCmd+Option+Ion a Mac, and select the Network tab. - Reload the page and let it finish. You will see the page's own files, its web fonts, and one anonymous page-view request. Nothing has been typed yet, so none of them can contain your headers.
- Click the clear icon in the Network tab so that the log is empty.
- Paste real headers into any lane and read the result.
- Look at the Network tab again. It is still empty. For extra proof, turn on offline mode after the page loads and every lane keeps working.
Only two things can add a line to that log, and neither carries your headers. Submitting the feedback form sends the vote and comment you typed. Typing characters in a script the page has not displayed yet, such as Cyrillic or Greek, can make the browser fetch the matching font file, and that request names only the font.
2http never sends a request on your behalf: the request builder writes code for you to run, and the meta inspector reads source you paste instead of fetching a URL. The production site also sends a Content-Security-Policy header that tells your browser to refuse connections to anywhere except this site and the anonymous analytics endpoint.