Your habit tracker runs in Expo Go. But Expo Go is a test tool. Your friends can't install "your app" from it, and Google Play can't accept it. You need a real Android file.

EAS Build is Expo's service that builds that file for you on its computers, in the cloud. You don't need Android Studio or a powerful laptop. Think of a tailor: you give the measurements (your code and app.json), they sew the shirt on their machine, and you get a link to collect it.

The first time, run these in your project folder:

npm install --global eas-cli
eas login
eas build:configure
eas build -p android --profile preview

eas build:configure creates a file called eas.json. It has three build profiles, like three recipes:

• development: a test build for developers. You don't need it yet.
• preview: a build to try on your own phone or share with friends.
• production: the build you upload to Google Play.

Android has two kinds of app file. An APK installs straight on a phone. An AAB (Android App Bundle) is what Google Play wants. You can't install an AAB yourself. Google Play turns it into the right APK for each phone. EAS makes an AAB by default, so for your own phone, add "buildType": "apk" to the preview profile:

"preview": {
  "distribution": "internal",
  "android": { "buildType": "apk" }
}

The first build asks to make a keystore. Say yes. It is the secret key that proves an update comes from you. EAS keeps it safe on its servers.

Every app has two version numbers. version (like 1.0.0) is what people see. versionCode (1, 2, 3...) is a hidden whole number for Google Play. Every upload to Play needs a bigger versionCode. Play won't take a versionCode it has already seen. The eas.json that eas build:configure makes sets appVersionSource to remote and autoIncrement to true for production, so EAS adds one for you on every production build.

The free plan is enough for this course. As of October 2026, expo.dev/pricing says it includes up to 15 Android builds, with low priority. The Expo docs say the free limits reset every month. A build can wait in a queue, sometimes 90 minutes or more at busy times, so start it and do something else.

People often build production first, send the .aab to a friend, and nothing opens. Use preview with apk for phones, and production only for Google Play.

When you read build output, look for three things: which profile it used, the line with the build details link, and at the end the link to your .apk or .aab. If it fails, open the build details link and read the first red error in the logs.