HTTP 301 Moved Permanently vs 431 Request Header Fields Too Large
HTTP 301 (Moved Permanently) is a 3xx Redirection response, while 431 (Request Header Fields Too Large) is a 4xx Client Error response. 301 indicates that the resource has been permanently moved to a new URL. All future requests should use the new URL. Search engines will transfer link equity to the new URL. 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 resource has been permanently moved to a new URL. All future requests should use the new URL. Search engines will transfer link equity to the new URL.
When You See It
After domain migrations, URL restructuring, or when consolidating duplicate URLs.
How to Fix
Update links and bookmarks to the new URL in the Location header. For SEO, this is the preferred redirect for permanent moves.
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
301 is a 3xx Redirection response, while 431 is a 4xx Client Error response.
HTTP 301: The resource has been permanently moved to a new URL. All future requests should use the new URL. Search engines will transfer link equity to the new URL.
HTTP 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
You encounter 301 when after domain migrations, URL restructuring, or when consolidating duplicate URLs.
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 301 (Moved Permanently): Update links and bookmarks to the new URL in the Location header. For SEO, this is the preferred redirect for permanent moves. For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens.