This week in caching: how to actually debug a cache

This week in caching: how to actually debug a cache
Four tools for "is this thing even caching?"
— read the right headers — X-Cache: HIT/MISS, CF-Cache-Status, X-Cache-Hits, Age. The Age header alone tells you object freshness instantly.
— curl -sI plus the cache buster — request twice; second hit should flip MISS to HIT. If it never does, your Vary or Set-Cookie is the culprit.
— RedBot.org — Mark Nottingham's tool reads your Cache-Control and tells you exactly how caches will treat the response.
— Chrome DevTools "Size: (disk cache)" — confirms the browser served locally, no network.
Bookmark: RedBot — paste a URL, get a plain-English verdict on every caching header.