Flutter - Different Build Modes

Flutter is the technology used to develop cross-platform applications for iOS, Windows, and Android using a single codebase. Flutter is backed by many strong features like hot reload and hot restart which makes it a favorite of all. In Flutter, build mode refers to the way your application is built and compiled. Based on different phases of development, Flutter compiles the code in different manners. When you simply build your flutter project you see a debug banner at the top-right, we will study that and other build modes supported in Flutter.

Why Build Modes?

If you are a native mobile application developer, you know how time-consuming the compilation is! Even the smallest colour correction in clones of apps like WhatsApp or Twitter takes hours to reflect. Flutter team introduced different build modes based on the development phase to ensure lightning-fast compilation speed. Due to this feature, modifications in the app do not make the whole code compile again and again.

Note: Build modes allow you to create optimized versions of your app for different purposes, such as development, testing, and production.

Types of Build Modes

There are 3 types of build modes during the compilation of the Flutter app

1. Debug Mode: deals with the development of the app/inspection of the code.
2. Profile Mode: deals with testing the performance of the app/profiling the performance of the app.
3. Release Mode: deals with the release of the app/removes the debugging information.

Let’s discuss each in detail.

1. Debug Mode

This is the default build mode used during development. In debug mode, Flutter enables various debugging features such as hot-reload, observatory, and additional runtime checks. The application will have a huge apk size, but it also offers faster construction time because of the hot reload feature. You can actively build and test your application with the help of debug mode. Simply pressing F5 in VSCode or the build button in the Android Studio project starts debug mode.

• Compiler used: dartdevc
• Features:
  • Assertions are enabled.
  • Service extensions are enabled.
  • Debugging is enabled.
  • You can debug your app on a physical device, Emulator or Simulator

Command to compile app using Debug mode:

flutter run

2. Profile Mode

Profile mode is designed to provide a balance between the features of debug and release modes. In this we can know which portion of our application is slow or fast. Profile mode helps you monitor the performance of your application and spot possible problems without compromising too much on speed. The apk size is smaller than that we get after debug or release mode.

Note: Profile mode requires an actual device or some latest emulator to function.

• Compiler used: dart2js
• Features:
  • Profile mode requires an actual device or some latest emulator to function.
  • Tracing is enabled.
  • Some service extensions to analyze performance are enabled.
  • Tooling support for DevTools is also enabled.

Command to compile app using Profile mode:

flutter run --profile

3. Release Mode

Release mode is used for producing optimized and smaller binary files that are suitable for distribution. The code is greatly optimized and debug symbols and other debugging tools are removed while generating your Flutter app in release mode. As a result, the software runs faster. The apk produced after this will have the actual size of application/project. Release mode is typically used when you are ready to deploy your app to production.

Note: Profile mode requires an actual device or some latest emulator to function.

• Compiler used: dart2js
• Features:
  • Assertions are disabled.
  • Debugging information is stripped out.
  • Debugging is disabled.
  • Service extensions are also disabled.
  • Release mode builds don’t support Emulator and Simulator.

Command to compile app using Release mode:

flutter run --release

Conclusion

This glimpse of build modes is sufficient to answer about the topic in interviews. As an Flutter developer, you will realize the importance of these three build modes at some stage of your project. These should be used be used during development for optimising the development phase of project.