Tells web browsers that the page or file being requested has not changed from the last time they requested it.

Most browsers will then use their cached previously-downloaded version if available.


This action will result in a response type of:

HTTP/1.1 304 Not Modified


…as opposed to a normal:

HTTP/1.1 200 OK


When receiving a 304 Not Modified, most browsers will cancel the download of content and ignore it if they have a previously provided 200 response in their cache.