Last-Modified and If-Modified-Since check

Checks the server response headers for Last-Modified and the server response to a request with an If-Modified-Since header.

Checking Last-Modified and If-Modified-Since is one of the integral parts in website promotion; it is required to understand whether the server response headers are formed correctly. p>

Last-Modified is one of the server response headers, which reports the date the page was last modified; it helps to estimate how long ago the content on it was changed.

If-Modified-Since is the header sent to the server. Using it, the date is transmitted to understand whether the page has been changed since this date. If the content has changed, then the server will respond with the page in the same way as with a normal request, with a response code of 200. But if there have been no changes on the page, the server will return an empty page with the 304 Not Modified header.

If-Modified-Since is used by browsers to save traffic. If, for example, the requested page is present in the browser's cache, then it will create a request with the If-Modified-Since header. Next, if a 304 Not Modified response is returned, then the browser will show this page from its cache.

Correctly setting up the server's response to the If-Modified-Since header also has a positive effect on interaction with search engines, which save time on downloading an unchanged page and use it to process subsequent pages on the site.