This week in caching: browser cache headers, measured wins

This week in caching: browser cache headers, measured wins

Small header changes, real repeat-visit numbers:

— SaaS dashboard — adding Cache-Control: max-age=31536000, immutable to fingerprinted JS/CSS cut repeat-view requests by 73%; returning users hit a warm browser cache instead of 304-revalidating every file.
— Media site — moving from ETag-only to long max-age on images removed thousands of conditional requests/day; that alone dropped origin egress ~15%.
— Blog — stale-while-revalidate=86400 on HTML made navigations feel instant while content refreshed silently in the background.

The insight: 'immutable' tells the browser not to even send a revalidation request. That's the part most setups miss.

Bookmark: WebPageTest repeat-view waterfall — it shows exactly which assets your headers are failing to cache.