In the final lecture of Stanford’s Spring 2021 iteration of its CS193p course, we focus on multi-platform support, that is, making an application work on iPad, iPhone and macOS. We demonstrate how to adapt our EmojiArt iOS code to build a macOS app too, using a variety of example strategies for sharing the code across platforms. Building cross-platform applications always requires some platform-specific idiomatic support, but in SwiftUI, an enormous amount of the code we write can target all platforms. SwiftUI’s application infrastructure comes in especially handy here because it automatically handles all of the menu creation (which is only needed on the Mac).