Flutter: Abnormally Release sizes - ios

Question

While building on both platforms, I noticed the following:
app.ipa 190MB,
Runner - 427,3Mb
Apk 7,2MB
[✓] Flutter (Channel stable, v1.12.13+hotfix.5, on Mac OS X 10.14.5 18F132, locale en-IT)
• Flutter version 1.12.13+hotfix.5 at /Users/cosminrus/Utils/flutter
• Framework revision 27321eb (3 months ago), 2019-12-10 18:15:01 -0800
• Engine revision 2994f7e1e6
• Dart version 2.7.0
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
• Android SDK at /Users/cosminrus/Library/Android/sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-29, build-tools 29.0.2
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
• All Android licenses accepted.
[✓] Xcode - develop for iOS and macOS (Xcode 11.3)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 11.3, Build version 11C29
• CocoaPods version 1.8.4
[✓] Android Studio (version 3.5)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 42.1.1
• Dart plugin version 191.8593
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
[✓] VS Code (version 1.41.1)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.7.1
[!] Connected device
! No devices available
! Doctor found issues in 1 category.

Answer 1

Flutter build sizes depends on the build execution is being used. For context, JIT and AOT are the both logics being used by Flutter to be really powerful.
JIT: Allows to do hot reload and see real time changes, the cons is that huge build size.
AOT: Builds on native code allowing Flutter to run full speed, build sizes are smaller.
You'd notice this on Android as well while checking its size on debug vs release mode.
To get a better idea of how much your app's size is going to be, run the following commands on terminal:
Android
flutter build apk --split-per-abi
and check the output file sizes.
iOS
flutter build ios && tar -zcf build/app.ipa build/ios/iphoneos/Runner.app && ls -lh build/app.ipa
If you want to dig into reducing file size, follow this LINK. And if you want to know why iOS builds are larger, check this LINK.
There's an official DOCS for build sizes if you're interested.