There’s a shift happening in how mobile apps are built—again. While a few years ago we moved from languages created in the 1980s and ʼ90s (think Objective-C and Java) toward more modern and expressive programming languages (Swift and Kotlin), we’re now seeing the transition from imperative to declarative UI frameworks in the form of SwiftUI and Jetpack Compose. This once again promises to dramatically increase developer productivity. To understand declarative UI’s present potential, it helps to start by exploring its not-too-distant past. Along the way, we’ll look at how it’s empowering developers to build apps faster with less code, and why now is the right time to consider adopting SwiftUI and Jetpack Compose.