HTTP 411 Length Required vs 431 Request Header Fields Too Large
Both HTTP 411 (Length Required) and 431 (Request Header Fields Too Large) belong to the 4xx Client Error category. 411 indicates that the server refuses to accept the request without a Content-Length header. 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 refuses to accept the request without a Content-Length header.
When You See It
When sending a request body without specifying Content-Length.
How to Fix
Include a Content-Length header in your request.
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 411: The server refuses to accept the request without a Content-Length header.
HTTP 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
You encounter 411 when when sending a request body without specifying Content-Length.
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 411 (Length Required): Include a Content-Length header in your request. For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens.