Flutter

Flutter is Google's open-source UI toolkit for building natively compiled applications for mobile, web, and desktop from a single Dart codebase. One codebase produces an iOS app, an Android app, a web app, and a macOS/Windows/Linux desktop app. That's the pitch, and it actually delivers—with caveats. Flutter works differently from React Native and other cross-platform frameworks. Instead of wrapping native UI components, Flutter renders every pixel itself using its own rendering engine (Impeller on iOS/Android, Skia as a fallback). This means your app looks identical on every platform—same fonts, same spacing, same animations—because Flutter isn't using the platform's native buttons, text fields, or scroll physics. The upside: pixel-perfect consistency. The downside: your app doesn't automatically get iOS-style swipe-to-go-back or Android's material ripple effects unless you implement them. Hot reload is Flutter's best developer experience feature. Change code, hit save, and the running app updates in under a second while preserving its current state. You're editing a form and want to change the button color? Save and see the change without re-entering form data or navigating back to that screen. This iteration speed makes UI development faster than native development in Swift or Kotlin, where builds take 15-60 seconds. Dart is the programming language Flutter uses. Most developers' first reaction to Dart is "why not JavaScript/TypeScript?" After a week, most come around. Dart is a typed language with null safety, async/await, and a garbage collector tuned for UI rendering (generational GC that doesn't cause frame drops). It compiles ahead-of-time (AOT) to native ARM code for production builds and just-in-time (JIT) for development builds (which is what enables hot reload). Flutter's widget system is its core abstraction. Everything is a widget—buttons, layouts, text, padding, themes, gesture detectors, animations. You compose widgets by nesting them. A screen is a tree of widgets. State management (Provider, Riverpod, BLoC) handles data flow through the widget tree. The learning curve is real if you come from HTML/CSS, but the mental model is consistent once you internalize it.