HTTP 103 Early Hints vs 431 Request Header Fields Too Large
HTTP 103 (Early Hints) is a 1xx Informational response, while 431 (Request Header Fields Too Large) is a 4xx Client Error response. 103 indicates that used to return some response headers before the final HTTP message. Allows the browser to start preloading resources while the server prepares the 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
Used to return some response headers before the final HTTP message. Allows the browser to start preloading resources while the server prepares the response.
When You See It
When a server wants the browser to start loading CSS/JS before the full response is ready.
How to Fix
No fix needed. This optimization helps speed up page loading.
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
103 is a 1xx Informational response, while 431 is a 4xx Client Error response.
HTTP 103: Used to return some response headers before the final HTTP message. Allows the browser to start preloading resources while the server prepares the response.
HTTP 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
You encounter 103 when when a server wants the browser to start loading CSS/JS before the full response is ready.
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 103 (Early Hints): No fix needed. This optimization helps speed up page loading. For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens.