Code obfuscation is the process of modifying an app’s binary to make it harder for humans to understand. Obfuscation hides function and class names in your compiled Dart code, making it difficult for an attacker to reverse engineer your proprietary app.
The following list describes which platforms support the obfuscation process described in this page:
- Supported as of Flutter 1.16.2. To obfuscate an app built against an earlier version of Flutter, use the obfuscation instructions on the Flutter wiki.
- macOS (in alpha as of Flutter 1.13), supports obfuscation as of Flutter 1.16.2.
- Not yet supported.
- Obfuscation is not supported for web apps, but a web app can be minified, which is similar. When you build a release version of a Flutter web app, it is automatically minified. For more information, see Build and release a web app.
Flutter’s code obfuscation, when supported, works only on a release build.
Obfuscating your app
To obfuscate your app, build a release
version using the
combined with the
--split-debug-info flag specifies the
directory where Flutter can output debug files.
This command generates a symbol map.
targets are currently supported. (
supported on the master and dev channels.)
flutter build apk --obfuscate --split-debug-info=/<project-name>/<directory>
Once you’ve obfuscated your binary, save the symbols file. You need this if you later want to de-obfuscate a stack trace.
Note that the
--split-debug-info flag can also
be used by itself. In fact, it can dramatically
reduce code size. For more information on
app size, see Measuring your app’s size.
For detailed information on these flags, run the help command for your specific target, for example:
flutter build apk -h
If these flags are not listed in the output,
flutter --version to check your version of Flutter.
Reading an obfuscated stack trace
To debug a stack trace created by an obfuscated app, use the following steps to make it human readable:
Find the matching symbols file. For example, a crash from an Android arm64 device would need
Provide both the stack trace (stored in a file) and the symbols file to the
flutter symbolizecommand. For example:
flutter symbolize -i <stack trace file> -d /out/android/app.android-arm64.symbols
For more information on the
flutter symbolize -h.
Be aware of the following when coding an app that will eventually be an obfuscated binary.
- Code that relies on matching specific class, function,
or library names will fail.
For example, the following call to
expect()will not work in an obfuscated binary: