Cache headers can't ensure that your site works offline—that's a big difference. There's Application Cache, but it's treacherous and deprecated. Service Worke

Cache headers can't ensure that your site works offline—that's a big difference. There's Application Cache, but it's treacherous and deprecated. Service Workers get near-total control over outgoing HTTP requests, which has many various uses. Then there are the coming features. You'll be able to push messages to your service worker even if your site isn't open in any tabs, for example.