Imagine building a mobile app. In the past, you'd need two separate teams: one to write code for iPhones (iOS) and another for Android devices. This meant double the work, double the cost, and double the time. React Native changed that.

React Native is a framework that lets developers build mobile apps for both iOS and Android using a single programming language: JavaScript. The code you write is compiled into native user interface elements, so the final app doesn't feel like a website squeezed onto a phone. It feels like a real, native app, with the smooth performance and animations users expect.

This “write once, run anywhere” approach is a game-changer. But setting up a new React Native project can be complex, involving configuration for each platform's specific build tools. That's where Expo comes in.

Expo provides what's called a managed workflow. This means Expo takes care of all the complicated native configuration for you. You can focus entirely on writing JavaScript code and building your app's features.

One of the biggest perks is the Expo Go app. You download it on your phone, scan a QR code from your computer, and your app instantly appears on your device. As you make changes to your code, the app updates in real-time. This makes testing and iterating incredibly fast.

Expo also comes with a rich library of pre-built APIs. Need to access the camera, location services, or contacts? Instead of writing complex native code, you can use a simple JavaScript function from the Expo SDK.

The managed workflow is fantastic for most apps, but it has one key limitation: custom native code.

Because Expo manages the native side of things, you can only use the native modules and components that the Expo SDK provides. If your app needs a very specific, niche feature that requires writing your own native code for iOS or Android—or using a third-party React Native library that includes custom native code—you can't do it in the managed workflow.

This isn't a dead end. If you start with the managed workflow and later find you need more control, Expo allows you to transition to a “bare workflow.” This gives you full native control, just like a standard React Native project, while still letting you use the parts of the Expo platform you find helpful. For beginners, however, starting with the managed workflow is almost always the right choice.

Time to check your understanding of these core concepts.

Understanding the roles of React Native and Expo, and the trade-offs of the managed workflow, is the first step in building powerful cross-platform apps.