How I Cut My App’s Build Size by 50% in Flutter

Build size is one of the most critical aspects of mobile app development, especially if you're targeting users in regions with limited internet access or data caps. Recently, I managed to reduce my Flutter app’s release build size by nearly 50%, and in this post, I’ll share exactly how I did it — step by step.

Why Build Size Matters

A bloated app build not only takes longer to download but can also impact your app’s install rate and even ranking on app stores. Optimizing your app size leads to:

• Faster downloads

• Lower storage usage

• Better performance on low-end devices

• Improved user experience

Initial Build Size Analysis

To start, I ran the following command to analyze my app's current size:

flutter build apk --analyze-size

This generated a .json file I could open in the Flutter DevTools size analyzer.

Results:

• Initial APK size: 36.2 MB

• After optimizations: 18.1 MB

Let’s break down the optimizations I applied.

1. Remove Unused Packages

I checked my pubspec.yaml and removed unused dependencies:

# Before
dependencies:
  http:
  provider:
  firebase_analytics:
  charts_flutter:
  flutter_html:

I removed charts_flutter and flutter_html, which were not in active use. Then ran:

flutter pub get

Savings: ~2.5 MB

2. Use Tree Shaking for Icons

If you're using MaterialIcons, Flutter includes the whole icon set by default.

To fix this, I used flutter_launcher_icons and custom icon fonts instead of importing the entire icon library.

Also, add this in pubspec.yaml:

flutter:
  uses-material-design: false

Savings: ~1.8 MB

3. Split Per ABI

Instead of generating a fat APK that supports all architectures, I created APKs per ABI:

flutter build apk --split-per-abi

This gave me separate APKs for armeabi-v7a, arm64-v8a, and x86_64.

Savings: Up to 60% for specific architectures

4. Compress and Resize Assets

I had several high-res images in the assets folder. I:

• Compressed PNGs using TinyPNG

• Resized large images

• Used WebP format where possible

Savings: ~3.2 MB

5. Use ProGuard (for Android)

ProGuard helps strip unused code from dependencies. I enabled it by editing android/app/build.gradle:

buildTypes {
    release {
        shrinkResources true
        minifyEnabled true
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
}

Savings: ~4 MB

6. Remove Debug Info

Always build with the --release flag and ensure no debug info is bundled.

flutter build apk --release

Also, avoid logging in production builds.

7. Use Deferred Components (Optional)

Flutter now supports deferred components (Android only), letting you load parts of the app on demand. This requires setup on both the Flutter and Android side.

More here: Flutter Deferred Components

Final Thoughts

Cutting down your Flutter app's build size doesn't have to be rocket science. Start with an analysis, then iterate through removal of unused packages, asset optimization, ABI splitting, and enabling ProGuard.

Total size saved: ~18 MB (50%)

If your users are in bandwidth-sensitive markets, this can make a huge difference in adoption and retention.

Over to You!

Have you tried optimizing your Flutter app size? Got any other tricks up your sleeve? Let me know in the comments or connect with me.