EAS Build

EAS Build is Expo's cloud build service. You push a config, EAS builds an iOS .ipa or Android .apk / .aab in its cloud, you download it. No Xcode on your machine required. This lesson covers the setup.

One-time install

$npm install -g eas-cli
$eas login   # uses your Expo account

The config — eas.json

Scaffolded into apps/mobile/eas.json:

{
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal"
    },
    "preview": {
      "distribution": "internal",
      "android": { "buildType": "apk" }
    },
    "production": {
      "autoIncrement": true
    }
  },
  "submit": {
    "production": {}
  }
}

Three profiles to know:

• development — dev build, JS hot-reloads live. Use during day-to-day dev.
• preview — APK / IPA you send to testers. Distributed via internal links.
• production — what goes to the App Store / Play Store. Auto-increments build number.

Your first preview build

# from apps/mobile/
$eas build --platform android --profile preview

First run prompts you to:

1. Configure a project ID (one-time per project)
2. For iOS: log in to Apple Developer account so EAS can sign with your cert
3. For Android: pick auto-managed signing or upload your keystore

Then it queues the build. You get a URL to track progress. ~10 minutes later, downloadable APK / IPA.

Installing the preview build

• Android APK: download, copy to phone, install (enable "install from unknown sources"). Or use the EAS QR.
• iOS: you need TestFlight (covered in the next lesson) — APKs don't exist on iOS for unsigned distribution.

Versioning

Two numbers matter:

• version (in app.json) — what the user sees ("v1.2.3"). Bump manually for marketing-visible releases.
• build number / version code — internal monotonically increasing integer. EAS auto-increments with the production profile.

The store rejects builds with duplicate build numbers. Let EAS manage this.

What gets built into the binary

Build-time environment is locked in: app.json,app.config.ts, and any process.env baked in via extra in app.json. Runtime config (API URL, feature flags) flows through Constants.expoConfig.extra:

export default ({ config }) => ({
  ...config,
  extra: {
    apiUrl: process.env.EAS_API_URL ?? 'http://localhost:8080',
    sentryDsn: process.env.EAS_SENTRY_DSN,
  },
})

Set the env vars in EAS dashboard or with eas secret:create for per-profile secrets.

What's next

Next lesson — submitting your build to the App Store and Play Store. The actual ship.