Bundle ID / Package name properly formatted

Bundle ID (iOS) and package name (Android) are the permanent, immutable identifiers that link every version of your app, every review, every user install, and every in-app purchase receipt to a single entity in the store databases. A malformed identifier — one that uses uppercase characters, hyphens, or has fewer than three segments — causes binary submission rejection before review begins. Using a generic placeholder like com.example.app in production is grounds for immediate rejection. Critically, once an app is published, changing the bundle ID or package name creates a brand-new app listing, breaking updates for all existing users. The Apple Bundle ID spec (apple-bundle-id) and Android Application ID spec (android-application-id) both mandate strict reverse domain notation.

Set both identifiers in app.json before first submission. Use strict reverse domain notation: all lowercase, alphanumeric segments only, each segment starting with a letter, minimum three segments.

// app.json
{
  "expo": {
    "ios": {
      "bundleIdentifier": "com.yourcompany.appname"
    },
    "android": {
      "package": "com.yourcompany.appname"
    }
  }
}

Choose this identifier before first TestFlight or Play Console submission — it cannot be changed without losing all existing installs and reviews. Avoid hyphens in any segment (they are illegal in both specs). Segments must not start with a digit.