This is because, until now, Swift has been changing so rapidly that each version required slightly different ‘glue’. With the release of macOS 10.14.4, and Xcode 10.2, apps written in Swift 5.0 won’t need those frameworks (except for compatibility when running on older macOS), as the ‘glue’ will be part of macOS, delivered with each new system update. Currently, no app written in Swift can run without this support, and it has to be duplicated in every single Swift app which you have on your Mac, even those which are still mostly written in Objective-C. It contains a load of dylibs, providing the glue between the app and macOS. Peek inside any app written in Swift – such as one of my recent free apps from Downloads above – and you’ll see a folder called Frameworks, which accounts for much of the size of the app, typically over 11 MB.

Before you abandon reading this thinking it’s relevant to those writing apps, not those using them, please bear with me: this will change your Mac, because it marks the moment that Swift becomes part of macOS. This isn’t something that users will notice immediately, but is the culmination of nearly a decade of heavy investment and the efforts of many of the finest software engineers: Swift 5.0.

But for once, it has officially informed us of a major change which is coming in macOS Mojave 10.14.4, probably due in around a month’s time, at the end of March. Apple so seldom pre-announces major changes in macOS, except at its annual WWDC which is still over three months away.

Objective c macos