React Native

React Native builds actual native mobile apps with native UI components, not a website wrapped in a phone frame. React Native is the most battle-tested way to do it. Write your app in JavaScript/TypeScript using React components, and it renders native iOS and Android UI. One codebase, two platforms.

This is Meta's own framework, used in Facebook, Instagram, and Messenger. That scale proves it works in production. The ecosystem is enormous: navigation libraries, UI kits, native module bridges, and thousands of community packages. The New Architecture (Fabric renderer, TurboModules) has made performance significantly better than the old bridge-based system.

Completely free under MIT. No paid tier from Meta. Flutter is the main competitor: Dart instead of JavaScript, pixel-perfect rendering instead of native components. Expo simplifies React Native development significantly by handling the native toolchain for you. If you're starting fresh with React Native, start with Expo, not bare React Native.

The catch: "learn once, write anywhere" still means platform-specific work. Complex animations, native APIs, and platform-specific UI patterns require writing native code (Swift/Kotlin) or finding a library that bridges it. Debugging can be painful; you're debugging across JavaScript, native, and the bridge layer. Build times are slow. And the upgrade path between versions has historically been rough, though it's improving.