App icon meets platform size requirements

App stores validate icon assets during binary review — a missing density bucket or broken path in app.json causes immediate rejection before a human reviewer ever sees your app. Android's adaptive icon system requires exact pixel dimensions at each mipmap density (mdpi through xxxhdpi); a missing xxxhdpi icon renders as a blurry, pixelated smear on flagship Pixel and Samsung devices. Apple's HIG requires discrete sizes for each display context (home screen, Spotlight, Settings). A single absent size silently fails submission. Beyond rejection, incorrectly sized icons degrade the visual identity of your app on every device class that uses the missing density, directly undermining user trust at the moment of first impression.

Generate a complete platform icon set from a 1024x1024 master (no pre-rounded corners — the OS applies rounding). For Expo projects, reference the master in app.json and let EAS export platform sizes; for bare React Native, export directly into the platform directories.

// app.json (Expo)
{
  "expo": {
    "icon": "./assets/icon.png",
    "android": {
      "adaptiveIcon": {
        "foregroundImage": "./assets/adaptive-icon.png",
        "backgroundColor": "#ffffff"
      }
    }
  }
}

For bare React Native Android, place PNGs at the correct pixel dimensions under android/app/src/main/res/mipmap-mdpi/ (48×48) through mipmap-xxxhdpi/ (192×192). For iOS, populate the Images.xcassets/AppIcon.appiconset/ catalog with 120×120, 152×152, 167×167, and 180×180 variants.