HTTP 203 Non-Authoritative Information vs 431 Request Header Fields Too Large
HTTP 203 (Non-Authoritative Information) is a 2xx Success response, while 431 (Request Header Fields Too Large) is a 4xx Client Error response. 203 indicates that the response payload has been modified by a transforming proxy from the origin server's 200 response. In contrast, 431 means that the server refuses to process the request because an individual header field or all headers collectively are too large.
Description
The response payload has been modified by a transforming proxy from the origin server's 200 response.
When You See It
When a proxy or CDN modifies the response body (e.g., adds headers, transforms content).
How to Fix
Check if a proxy is modifying the response. Access the origin directly if you need the original content.
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.
Key Differences
203 is a 2xx Success response, while 431 is a 4xx Client Error response.
HTTP 203: The response payload has been modified by a transforming proxy from the origin server's 200 response.
HTTP 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
You encounter 203 when when a proxy or CDN modifies the response body (e.g., adds headers, transforms content).
You encounter 431 when when cookies accumulate to an excessive size, or a single header (like Authorization) is too long.
When to Use Which
For 203 (Non-Authoritative Information): Check if a proxy is modifying the response. Access the origin directly if you need the original content. For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens.