Please mind that “Browsers that support Progressive Web Apps” is not a real term, PWA itself is a set of features that a web app can provide for users. So it’s not just only about Service Worker and App Manifest.
Check out: Baseline PWA Checklist.
Here are what you can do to achieve PWA on iOS/Safari at the moment this answer is created:
- Site is served over HTTPS ✅
- Pages are responsive on tablets & mobile devices ✅
- The start URL (at least) loads while offline 🚫
- Metadata provided for Add to Home screen ✅❗️
- The first load is fast even on 3G ✅
- Site works cross-browser ✅
- Page transitions don’t feel like they block on the network ✅
- Each page has a URL ✅
As you can see, almost everything is working, even if your page can’t work offline on iOS/Safari, there is still a huge benefit of “upgrading” your web app into a PWA.
What you really want is not the fancy title of “Progressive Web Apps” but a good web app that delivers a good experience and features for users. This is a journey as you can accomplish it by each small part, that’s why it is called “Progressive”.
Note on the “Add to Home screen: Safari has its own spec for “Home screen icon” called apple-mobile-web-app-capable in the meta tags. Web App Manifest Generator has a fallback for iOS using this meta tags.