Variant Also Negotiates

5xx Server Error

ELI5

The server got confused while picking the best version of a resource and ended up pointing in circles.

Server perspective

Use 506 for a transparent content negotiation misconfiguration where the selected variant is itself negotiable and causes a loop or invalid resolution path.

When to use

•Return 506 only for transparent content negotiation configuration errors
•Use it when the server cannot deliver a concrete representation because variant metadata is self-referential
•Transparent content negotiation is enabled and the selected variant is also negotiable
•Server configuration creates a circular variant selection path
•Negotiated representations cannot be resolved because the variant map is self-referential

How to respond

•Fix the variant map, rewrite rules, or negotiated-resource metadata so each negotiable resource resolves to concrete variants
•Log which variant selection path caused the loop so operators can repair the configuration quickly

Headers to consider

•No status-specific header is required; standard negotiation headers may still appear, but the main fix is server-side configuration

Response body

•A body is helpful; explain that content negotiation configuration is invalid and include a request or trace ID for support

Server-side pitfalls

•Do not use 506 for ordinary Accept or Accept-Language mismatches; that is usually 406 Not Acceptable
•Do not blame the client for a server-side negotiation loop
•The client asked for an unavailable representation and the server can describe acceptable alternatives (use 406 Not Acceptable)
•The server hit a generic unexpected fault unrelated to negotiation configuration (use 500 Internal Server Error)
•Multiple valid variants exist and the server wants the client to choose (use 300 Multiple Choices)

Examples

Misconfigured negotiated variant

Request:GET https://api.example.test/manual

Response:

506 Variant Also Negotiates

# Headers
Content-Type: application/json

# Body
{
  "error": "variant_also_negotiates"
}

The server's negotiated French variant points to another negotiable resource instead of a concrete representation.

References

Related Status Codes

300

Multiple Choices

There are several valid versions of this thing, and the server is asking you to pick one.

406

Not Acceptable

I can't give you the data in the format you want. I have the data, but not in XML/JSON/etc. that you asked for.

500

Internal Server Error

Something broke on our end! It's not your fault - our server had a problem and couldn't handle your request.