Caching

Caching is the practice of storing copies of resources so they can be served faster on later requests instead of being regenerated or refetched every time.

Caching happens at several layers. Browser caching stores assets like CSS, JavaScript, and images on the visitor's device so repeat visits avoid re-downloading them. Server-side and page caching store rendered HTML so the server skips rebuilding a page for every request. A content delivery network caches copies at edge locations near users. Each layer trims work and latency between a request and a response.

For SEO the payoff is speed and stability. Faster responses improve load metrics that feed Core Web Vitals and the page experience signals, and a cached page holds up better under traffic spikes or heavy crawling. Lower server load also means crawlers can fetch more pages in the time they allot, which helps crawl efficiency on large sites.

Caching is controlled mainly through HTTP headers such as Cache-Control and ETag, which tell clients how long to keep a resource and how to check whether it changed. The main risk is staleness: an over-aggressive cache can serve outdated content, including old prices or removed pages, so cache durations should match how often content changes and you need a way to purge entries on update. Caching pairs naturally with a CDN, which distributes those cached copies geographically.

Related: CDN (Content Delivery Network), LCP Complete Guide, Crawl Budget Explained