Expiration Date (Cache)

What Is an Expiration Date on the Web?

A well-configured expiration date can reduce load times for returning visitors by 50–80% — one of the best performance optimizations with minimal effort. Static resources like logos and stylesheets can be cached for one to two years, while HTML content needs shorter expiration times. PageSpeed Insights shows you immediately where caching opportunities exist on your website.

The expiration date, also referred to as Expires or Cache-Control, is an HTTP header that instructs a browser or intermediate cache how long it may store a web resource before a fresh version must be fetched from the server. A correct expiration date is essential for page speed: when images, CSS, and JavaScript can be cached, these resources do not need to be downloaded again on every visit. This saves bandwidth, reduces server load, and significantly improves load times for returning visitors. Google considers efficient caching as part of the page experience evaluation.

Technically, the expiration date is defined through Cache-Control headers: Cache-Control: max-age=2592000 means, for example, that the resource can be cached for 30 days. There is also the Expires header (an older variant) and ETag/Last-Modified for cache validation. The server can also specify whether a resource is public or private and whether it must be revalidated before use. A poor caching setup unnecessarily burdens the server and slows website load times — this directly affects Core Web Vitals, especially LCP.

In practice, define different cache durations for different resource types: static resources like logos or stylesheets can be cached for 1–2 years (max-age=31536000). Images and fonts can be set to 30–90 days. HTML files should be cached for shorter periods (a few days) or not at all, so users see current content. Browser cache can also be controlled via .htaccess (on Apache) or through CDN settings. Tools like PageSpeed Insights show where caching opportunities exist. Well-configured caching reduces load times for returning visitors by 50–80% — one of the best ROI optimizations for page speed.