Is ServiceWorker intended to replace Appcache, or is the intention that the two will coexist? Phrased another way, is appcache about to become deprecated?
Blink's Service Worker team is keen on deprecating AppCache (We will follow our usual intent to deprecate process). We believe that Service Worker is a much better solution. Also, it should be pretty easy to offer a drop-in replacement for AppCache built on top of SW. We'll start by collecting usage metrics and do some outreach.
AppCache and Service Worker should coexist without any issue since offering offline support via AppCache for browsers that don't support Service Workers is a valid use case. @flo850 If it's not working, please let us know by filing a bug.
I must say that Services Worker is not only the replacement for AppCache, but it’s far more capable. An AppCache can’t be partially updated, a byte-by-byte manifest comparison to trigger the update seems odd and there are several use cases leading to security and terrible usability problems.
Even Chrome and Firefox are planning to stop support for AppCache in the near future. Now that service workers are supported by Chrome, Opera, and Firefox.Also, The noises coming from Microsoft and Safari have been positive with respect to implementation and under consideration.
As a cache tool, it will coexist with appcache. Appcache works on virtually every browser.
But service workers are a solid foundation that will permit new usage like push (even when the browser is in the background) , geofencing or background synchronization.
来源：https://stackoverflow.com/questions/28271843/is-service-worker-intended-to-replace-or-coexist-with-appcache