Expo — Universal Native Apps for iOS, Android & Web

What it is

Expo is an open-source framework and platform built on top of React Native. It lets you build native mobile apps for iOS and Android, plus web apps, all from a single JavaScript/TypeScript codebase. Expo provides a managed workflow with over 100 prebuilt native modules, an OTA (over-the-air) update system, and the EAS Build cloud service for compiling native binaries without local Xcode or Android Studio setups.

Expo targets mobile developers, startup teams, and frontend engineers who want to ship cross-platform apps without managing native build toolchains directly.

How it saves time or tokens

Expo's managed workflow eliminates the need to configure Xcode, Gradle, and native module linking manually. The EAS Build service compiles your app in the cloud, cutting local build times to zero. OTA updates let you push JavaScript changes instantly without going through App Store review cycles. For teams, this means faster iteration and fewer native build failures.

The Expo SDK bundles common native APIs (camera, file system, notifications, maps) as drop-in modules, saving days of native integration work per feature.

How to use

1. Install the Expo CLI: npx create-expo-app my-app to scaffold a new project. Run npx expo start to launch the development server.
2. Write your app using React Native components and Expo SDK modules. Use Expo Go on your phone to preview changes instantly without compiling.
3. Build for production with eas build --platform all. Submit to app stores with eas submit or push OTA updates with eas update.

Example

import { Camera, CameraView } from 'expo-camera';
import { useState } from 'react';
import { Button, View } from 'react-native';

export default function CameraScreen() {
  const [permission, requestPermission] = Camera.useCameraPermissions();

  if (!permission?.granted) {
    return <Button title='Grant Camera Access' onPress={requestPermission} />;
  }

  return (
    <View style={{ flex: 1 }}>
      <CameraView style={{ flex: 1 }} facing='back' />
    </View>
  );
}

This component uses the Expo Camera module. No native linking or pod install required.

Related on TokRepo

• AI tools for coding — AI-assisted development tools for faster app building
• Automation tools — CI/CD and build automation for deployment pipelines

Common pitfalls

• Expo Go does not support all native modules. If you need a custom native module not in the Expo SDK, you must use a development build or eject to the bare workflow.
• EAS Build is free for limited builds per month. High-volume teams need a paid plan for faster queue times and more build slots.
• OTA updates only apply to JavaScript bundle changes. Native binary changes (new native modules, SDK version bumps) still require a full app store submission.