Safari is widely used and the unavailability of service workers to help adapt to not having a network connection sounded like a deal breaker. However, using portable browser storage APIs and JavaScript should be enough to write progressive apps that would also work on Safari, right?
As Service Worker is a progressive enhancement we can still use it even though Safari doesn't support it yet.
Safari still supports AppCache which SW is designed to replace (AppCache has some unfixable problems) so although it doesn't have the richness of SW it still has some declarative offline support
