Workers will be at your service in an upcoming release of Safari — specifically Safari Technology Preview 48, macOS High Sierra 10.13.4 and iOS 11.3 beta seed 2.

Youenn Fablet, software engineer at Apple, writes:

While WebKit’s implementation and feature set is quickly evolving, we believe it has reached an important milestone in terms of functionality and compliance: applications using service workers for offline support or network/cache optimizations run successfully on latest WebKit builds. Let’s now dive into the specifics…

There are threads on Twitter here and here you should check out for commentary on this spec.

This news comes after Microsoft announces PWAs are coming to Microsoft Edge and Windows.