HTTP Caching Explained for Frontend Developers
Cache-Control, ETag, and CDN behaviour — enough theory to debug stale bundles without memorising RFC chapters.
Table of Contents
HTTP Caching Explained for Frontend Developers
Caches sit everywhere — browser memory/disk, service workers, intermediaries, and edge POPs. Misaligned directives cause either stale UI or redundant downloads.
Cache-Control directives
max-age tells caches freshness seconds — immutable hashed assets pair well with long horizons plus filename fingerprints.
no-store differs from no-cache — the latter allows storing but forces revalidation semantics consumers often misunderstand.
Validators
ETag and Last-Modified enable 304 Not Modified responses — cheaper than reshipping bytes when nothing changed.
Debugging mindset
When users report “old UI”, trace which layer cached — SW skipWaiting, CDN purge, or aggressive browser tabs — before bumping versions blindly.
Ship cache-friendly asset naming (app.[hash].js) so aggressive caching stays safe after deploys.
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