A “304 Not Modified” status code is aa HTTP response that indicates that the requested resource has not been altered since the last time it was accessed. When a client, such as a web browser, makes a request for content and includes an “If-Modified-Since” or “If-None-Match” header, the server checks if the resource has changed since that specified date or ETag value.
If there have been no modifications to the resource, the server responds with a 304 status code instead of sending back the full content again. This optimises bandwidth usage and improves loading times by instructing clients to use their cached version of the resource rather than downloading it anew.
Search engines favour fast-loading websites, so efficient caching mechanisms supported by 304 responses can contribute positively to search rankings.
