HTTP 431 Request Header Fields Too Large vs 510 Not Extended
HTTP 431 (Request Header Fields Too Large) is a 4xx Client Error response, while 510 (Not Extended) 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, 510 means that further extensions to the request are required for the server to fulfill it.
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
Further extensions to the request are required for the server to fulfill it.
When You See It
When an HTTP extension required by the server is not present in the request.
How to Fix
Add the required extension headers to your request.
Key Differences
431 is a 4xx Client Error response, while 510 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 510: Further extensions to the request are required for the server to fulfill it.
You encounter 431 when when cookies accumulate to an excessive size, or a single header (like Authorization) is too long.
You encounter 510 when when an HTTP extension required by the server is not present in the request.
When to Use Which
For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens. For 510 (Not Extended): Add the required extension headers to your request.