HTTP 103 Early Hints vs 304 Not Modified
HTTP 103 (Early Hints) is a 1xx Informational response, while 304 (Not Modified) is a 3xx Redirection 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, 304 means that the resource has not been modified since the last request. The client can use its cached copy.
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 resource has not been modified since the last request. The client can use its cached copy.
When You See It
When the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
How to Fix
No fix needed. This saves bandwidth by confirming the cached version is still current.
Key Differences
103 is a 1xx Informational response, while 304 is a 3xx Redirection 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 304: The resource has not been modified since the last request. The client can use its cached copy.
You encounter 103 when when a server wants the browser to start loading CSS/JS before the full response is ready.
You encounter 304 when when the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
When to Use Which
For 103 (Early Hints): No fix needed. This optimization helps speed up page loading. For 304 (Not Modified): No fix needed. This saves bandwidth by confirming the cached version is still current.