Expo is an open-source and free platform that lets web developers build truly native apps that work across both iOS and Android by writing them once in just JavaScript. Use the Expo tag on questions about developing Expo projects and using the Expo development tools like XDE and exp.
Expo lets web developers build truly native and Web applications that work across iOS, Android and Web by writing them once in just JavaScript. It's an open source, free toolchain built on top of React Native.