The HTTP Status Code 506 means that a transparent content negotiation for the request results in a circular reference.
Frequently Asked Questions
What does HTTP 506 mean?
HTTP 506 Variant Also Negotiates is a server error status code returned when transparent content negotiation for a request results in a circular reference. The server detects that the variant it selected is itself configured to negotiate further, creating a loop it cannot resolve. Like all 5xx codes, the problem lies on the server side, not with the client.
When does a server return a 506 error?
A server returns 506 when it performs transparent content negotiation and the chosen variant points back to another negotiable resource rather than a final, concrete representation. This typically surfaces in Apache configurations where a type map file references another type map or a MultiViews setting creates an ambiguous negotiation chain. The server detects the condition and terminates the loop with a 506.
How do I fix an HTTP 506 error?
Fix a 506 by auditing your server's content negotiation configuration and ensuring every variant entry resolves to a static, non-negotiable file. In Apache type map (.var) files, each URI line must point to an actual resource file, not another map or negotiable URI. If the error persists, temporarily disabling content negotiation can restore service while you trace the circular reference offline.
What is the difference between HTTP 506 and HTTP 300?
HTTP 300 Multiple Choices is a successful response that presents the client with a list of variants to choose from, meaning negotiation is working as intended. HTTP 506, by contrast, signals that negotiation has broken down due to a server misconfiguration causing a circular reference. Where 300 is a normal part of content negotiation, 506 always indicates an error that must be fixed on the server.
How common is the HTTP 506 status code in practice?
The 506 status code is rarely seen in production. The transparent content negotiation mechanism it relates to was experimental and never became a widely adopted standard. Most modern applications handle content negotiation at the application layer using request headers like Accept and Accept-Language, which sidesteps the server-level negotiation that triggers a 506.
Does an HTTP 506 error affect SEO?
Yes. Search engines treat 506 like other 5xx server errors, and persistent failures signal that a page is unreliable. If a crawler repeatedly receives a 506, it will reduce the crawl rate for the affected URLs and may eventually drop them from the index. Resolving the underlying server misconfiguration promptly minimizes any negative crawl and indexation impact.
