Testing Android apps with Expo on physical devices

If you’re a web developer and you want to create mobile apps for iOS and Android, then you’ll probably use Expo¹. Expo allows you to write React Native² code and has a full development environment for both iOS and Android, as well as generating a web preview of the same application. Your development build integrates directly with iOS and Android emulators running on your local machine, making it easy to debug and rapidly make changes. However, there’s no replacement for testing on a physical device. For iOS, this is fairly straightforward so long as you’re on a Mac; for Android, it can be a bit trickier.

After trying out several approaches, I finally landed on attaching an Android device via USB to the same Windows machine running my Expo development server. This approach gives the device access to localhost, so I can run the API backend locally and have everything work. As a bonus, it even works when the dev server is running in WSL.

Step 1: Download and install Android Studio

To get started, follow the instructions to set up Android Studio³. Regardless of whether you’ll use Expo’s cloud service or local builds, you’ll still need this installed to get access to adb, the Android debug bridge.

Step 2: Set up your device for USB debugging

You’ll need to enable debugging via the USB connection for the rest of the steps to work:

1. Open your Android device and go to Settings > About phone > Software information.
2. Tap Build number seven times.
3. Go to Settings > Developer options.
4. Enable USB Debugging.

Connect your Android device to your computer with a USB cable. If everything is set up correctly, you should see your device when you run adb devices. It looks something like this:

$ adb devices
List of devices attached
RAB34TMQA     device

Step 3: Generate and load the build

Next, you’ll need the expo-dev-client package to connect to Expo-generated developer builds:

npx expo install expo-dev-client

If you’re building locally, you can run:

npx expo run:android

If you’re building using Expo Application Services, you can run:

eas build --platform android --profile development

In either case, scan the QR code to download the APK and install it on your device.

Step 4: Start your dev server

For active development, start your dev server locally with the --localhost flag:

npx expo start --localhost

The --localhost flag tells the dev server to bind directly to localhost and forego any IP address binding.

Open the development build on your device and you should see your dev server listed under “Development servers”. If not, continue on.

Step 5: Set up reverse proxies

If you’re still not seeing your dev server in the app, set up a reverse proxy using adb:

adb reverse tcp:8081 tcp:8081

You should see your dev server now. If not, try manually entering exp://localhost:8081.

Note: If your dev server needs access to other services running on localhost, be sure to add reverse proxies for those, too. For example, if you’re running your API server on port 8080, run the following:

adb reverse tcp:8080 tcp:8080

Conclusion

Testing your Expo app on a physical Android device doesn’t have to be complicated. By connecting your device via USB and using adb reverse proxies, you gain a fast, reliable development workflow that mirrors production conditions. This approach is especially powerful when combined with a local API backend, letting you develop and test end-to-end features without any external dependencies. Whether you’re using local builds or Expo Application Services, this setup gives you the confidence to catch bugs and refine your app’s behavior before it reaches users. As a bonus, it also works in complex development setups such as working in WSL on Windows.