A complete guide to HTTP caching

HTTP caching makes websites fast, reliable, and cost-effective, yet remains one of the most misunderstood aspects of web development. Many developers incorrectly use directives like "no-cache" (which actually means store but revalidate) or reach for "no-store" as a default, unknowingly breaking their caching strategy. Multiple layers work together - browsers, CDNs, proxies, and application caches - each interpreting headers like Cache-Control, ETag, and Vary differently. Proper caching strategy impacts four key areas: speed (eliminating unnecessary network trips), resilience (absorbing traffic spikes), cost (reducing expensive origin requests), and SEO (improving crawl efficiency and page performance).