HTTP 404 Not Found vs 431 Request Header Fields Too Large
Both HTTP 404 (Not Found) and 431 (Request Header Fields Too Large) belong to the 4xx Client Error category. 404 indicates that the server cannot find the requested resource. The URL may be wrong, the resource may have been deleted, or it may never have existed. Meanwhile, 431 means that the server refuses to process the request because an individual header field or all headers collectively are too large.
Description
The server cannot find the requested resource. The URL may be wrong, the resource may have been deleted, or it may never have existed.
When You See It
When a URL is mistyped, a page has been deleted, or an API endpoint doesn't exist.
How to Fix
Verify the URL is correct. Check for typos, case sensitivity, and trailing slashes.
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
HTTP 404: The server cannot find the requested resource. The URL may be wrong, the resource may have been deleted, or it may never have existed.
HTTP 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
You encounter 404 when when a URL is mistyped, a page has been deleted, or an API endpoint doesn't exist.
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 404 (Not Found): Verify the URL is correct. Check for typos, case sensitivity, and trailing slashes. For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens.