Check Last-Modified and If-Modified-Since

Why Last-Modified matters

The HTTP Last-Modified header tells clients when a resource was last changed. A browser or search crawler with a cached copy can send an If-Modified-Since request. If the resource has not changed, the server should respond with 304 Not Modified.

Save bandwidth

When a page has not changed, a 304 response sends headers without retransmitting the page, images or other resources.

Reduce server load

Checking the modification time before generating a dynamic page can avoid database queries, template rendering and other work. This is particularly useful for frequently updated pages that visitors request repeatedly, such as sports news and news aggregators.

Improve search engine crawling

Search engines recommend sending Last-Modified and handling If-Modified-Since correctly. Google can then tell whether content has changed since its last crawl, saving bandwidth and resources. Yandex likewise recommends accurate modification dates so crawlers can prioritize changed pages.