IconVault's HTTP Cache Lab is an interactive simulator for learning HTTP caching. Pick Cache-Control directives like max-age, no-cache, no-store, must-revalidate, immutable and stale-while-revalidate, set an ETag, then send requests and advance the simulated clock while a decision tree lights up to show exactly why each request was a cache hit, a miss, or a revalidation.

Watching the logic play out step by step makes abstract header rules concrete: what no-cache really does, when a 304 Not Modified replaces a full download, and how ETag comparison saves bandwidth. It is free with no signup and runs fully in your browser. The honest note: this is a teaching simulation of browser cache logic; real browsers, CDNs and proxies add extra layers like heuristic caching and shared caches that the lab intentionally keeps out.