Flutter Code Obfuscation

What is Obfuscation?

Replaces function/class names with obscure symbols to make reverse engineering harder.

Warning: Obfuscation only renames symbols - it does NOT encrypt resources or provide strong security. Never store secrets in the app.

Supported Platforms

| Platform | Build Targets | |----------|---------------| | Android | aar, apk, appbundle | | iOS | ios, ios-framework, ipa | | Desktop | linux, macos, macos-framework, windows | | Web | Not supported (uses minification instead) |

Build with Obfuscation

Basic Command

flutter build <target> \
  --obfuscate \
  --split-debug-info=<symbols-directory>

Examples

# Android APK
flutter build apk --obfuscate --split-debug-info=out/android

# Android App Bundle
flutter build appbundle --obfuscate --split-debug-info=out/android

# iOS
flutter build ios --obfuscate --split-debug-info=out/ios

# iOS IPA
flutter build ipa --obfuscate --split-debug-info=out/ios

# macOS
flutter build macos --obfuscate --split-debug-info=out/macos

# Windows
flutter build windows --obfuscate --split-debug-info=out/windows

# Linux
flutter build linux --obfuscate --split-debug-info=out/linux

Important: Backup the generated symbol files!

Symbol Files

Generated in <symbols-directory>:

out/android/
├── app.android-arm.symbols
├── app.android-arm64.symbols
└── app.android-x64.symbols

Always backup these files - required for crash report deobfuscation.

Deobfuscate Stack Traces

Command

flutter symbolize -i <stack-trace-file> -d <symbols-file>

Example

# Save crash stack trace to file
echo "crash stack trace content" > crash.txt

# Deobfuscate
flutter symbolize -i crash.txt -d out/android/app.android-arm64.symbols

Generate Obfuscation Map

Creates JSON mapping of original → obfuscated names:

flutter build apk \
  --obfuscate \
  --split-debug-info=out/android \
  --extra-gen-snapshot-options=--save-obfuscation-map=out/android/map.json

Output (map.json):

["MaterialApp", "ex", "Scaffold", "ey", "MyWidget", "ez", ...]

Limitations

Code That Will Break

// BAD: Runtime type checking fails after obfuscation
expect(foo.runtimeType.toString(), equals('Foo')); // ❌

// BAD: Type name comparison
if (widget.runtimeType.toString() == 'MyWidget') { } // ❌

What's NOT Obfuscated

Enum names (remain unchanged)
String literals
Asset paths

Quick Reference

| Task | Command | |------|---------| | Build obfuscated APK | flutter build apk --obfuscate --split-debug-info=out/android | | Build obfuscated IPA | flutter build ipa --obfuscate --split-debug-info=out/ios | | Deobfuscate crash | flutter symbolize -i crash.txt -d app.android-arm64.symbols | | Generate map | Add --extra-gen-snapshot-options=--save-obfuscation-map=map.json | | Check options | flutter build <target> -h |

Workflow Summary

1. Build with --obfuscate --split-debug-info=<dir>
2. Backup symbol files (*.symbols)
3. Distribute obfuscated app
4. When crash occurs: flutter symbolize -i <crash> -d <symbols>

Official Docs

Obfuscate Dart code