HTTP 103 Early Hints vs 421 Misdirected Request
HTTP 103 (Early Hints) is a 1xx Informational response, while 421 (Misdirected Request) 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, 421 means that the request was directed at a server that is unable to produce a response for the combination of scheme and authority in the URI.
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 request was directed at a server that is unable to produce a response for the combination of scheme and authority in the URI.
When You See It
With HTTP/2 when a connection is reused for a domain the certificate doesn't cover.
How to Fix
Retry the request on a new connection.
Key Differences
103 is a 1xx Informational response, while 421 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 421: The request was directed at a server that is unable to produce a response for the combination of scheme and authority in the URI.
You encounter 103 when when a server wants the browser to start loading CSS/JS before the full response is ready.
You encounter 421 when with HTTP/2 when a connection is reused for a domain the certificate doesn't cover.
When to Use Which
For 103 (Early Hints): No fix needed. This optimization helps speed up page loading. For 421 (Misdirected Request): Retry the request on a new connection.