App size optimization — ProGuard/R8, Hermes, ABI splits, asset compression?

App RN baseline ~25–40MB (iOS) / ~15–25MB (Android). Tối ưu xuống 10–20MB cho banking app, app SEA emerging market.

Android:

1. Hermes (default 0.70+): bytecode + smaller runtime → giảm 5–10MB so với JSC.

2. R8/ProGuard (default release): obfuscate + tree-shake unused Java code. Thêm rules tránh strip code dùng qua reflection:

-keep class com.facebook.react.** { *; }
-keep class com.swmansion.reanimated.** { *; }

3. ABI splits (android/app/build.gradle):

splits {
  abi {
    enable true
    reset()
    include 'arm64-v8a', 'armeabi-v7a'  // skip x86
    universalApk false
  }
}

Mỗi APK chỉ chứa native lib cho 1 ABI → giảm 30–50% size. Play Store chấp nhận multi-APK.

4. App Bundle (.aab) (recommend): Google chia chunk theo device → user download chỉ phần cần. Giảm 20–30% so với universal APK.

5. Resource shrinking: shrinkResources true trong release. Bỏ asset không reference.

iOS:

1. Bitcode (deprecated từ Xcode 14): không cần config nữa.

2. App Thinning: App Store tự thinning per-device — chỉ download asset cho device đó. Active by default.

3. Strip debug symbols: Strip Linked Product = YES trong release build settings.

Cross-platform:

• Image: dùng WebP/AVIF thay PNG/JPEG. Tool: expo-image tự pick format.
• Font subset: chỉ ship glyph cần. Tool glyphhanger hoặc Google Webfonts subset API.
• Lottie/JSON animation: minify, dedupe asset chung.
• Audit: npx react-native-bundle-visualizer xem JS bundle. apkanalyzer (Android Studio) cho APK.

Target số 2026: một app feature trung bình nên fit trong 25MB Android, 40MB iOS install size.