Expo (React Native)

Expo Go is a mobile app for iOS and Android that lets developers test React Native code on physical devices in real time by scanning a QR code generated by the Expo CLI. The JavaScript bundle loads over the local network, so changes appear almost instantly without rebuilding native code. This dramatically shortens the development iteration cycle compared to compiling with Xcode or Android Studio on every change.

No, React Native can be used independently through the React Native CLI with native build tools like Xcode and Android Studio. However, Expo significantly simplifies development by abstracting away native build configurations, managing permissions, and providing pre-built modules for common device features. Many developers start with Expo and transition to the bare workflow only when they need custom native code.

Starting with recent versions of Expo's SDK, a config plugins system allows developers to add custom native code without fully ejecting from the Expo ecosystem. For fully custom native modules, developers can use Expo's prebuild system or transition to the bare workflow, which provides full access to native iOS and Android project files. This has significantly reduced the situations where developers must leave Expo entirely.

EAS Build is a cloud-based service that compiles standalone iOS and Android app binaries without requiring local native build tools like Xcode or Android Studio. EAS Submit handles publishing those binaries to the Apple App Store and Google Play Store. EAS also includes an Update feature that pushes over-the-air JavaScript updates to deployed apps, allowing minor changes without going through app store review.