HTTP 431 Request Header Fields Too Large vs 506 Variant Also Negotiates
HTTP 431 (Request Header Fields Too Large) is a 4xx Client Error response, while 506 (Variant Also Negotiates) is a 5xx Server Error response. 431 indicates that the server refuses to process the request because an individual header field or all headers collectively are too large. In contrast, 506 means that the server has an internal configuration error: the chosen variant resource is configured to engage in content negotiation itself.
Description
The server refuses to process the request because an individual header field or all headers collectively are too large.
When You See It
When cookies accumulate to an excessive size, or a single header (like Authorization) is too long.
How to Fix
Reduce header sizes. Clear excessive cookies. Use shorter tokens.
Description
The server has an internal configuration error: the chosen variant resource is configured to engage in content negotiation itself.
When You See It
Rare. Indicates a misconfigured server-side content negotiation loop.
How to Fix
Fix the server's content negotiation configuration.
Key Differences
431 is a 4xx Client Error response, while 506 is a 5xx Server Error response.
HTTP 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
HTTP 506: The server has an internal configuration error: the chosen variant resource is configured to engage in content negotiation itself.
You encounter 431 when when cookies accumulate to an excessive size, or a single header (like Authorization) is too long.
You encounter 506 when rare. Indicates a misconfigured server-side content negotiation loop.
When to Use Which
For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens. For 506 (Variant Also Negotiates): Fix the server's content negotiation configuration.