In Flutter, “AOT” and “JIT” are two different compilation modes that the Flutter framework uses to execute Dart code on different platforms. These modes have distinct characteristics and purposes:
- AOT (Ahead-of-Time) Compilation:
- Purpose: AOT compilation is primarily used for producing release builds of Flutter applications. It compiles Dart code into native machine code ahead of time, resulting in highly optimized, standalone native executables for the target platform.
- Performance: AOT-compiled Flutter apps typically offer better performance than JIT-compiled apps. This is because they do not require an intermediate compilation step during runtime.
- Start-up Time: AOT-compiled apps generally have faster start-up times compared to JIT-compiled apps because the native code is already generated and does not need to be compiled just-in-time.
- Size: AOT-compiled apps tend to have larger binary sizes due to the inclusion of native code. However, Flutter has features like tree-shaking to help reduce unnecessary code in the final binary.
- Platform Compatibility: AOT compilation is platform-specific. You need to compile your Flutter app separately for each target platform (e.g., Android and iOS).
- Example: When you build and distribute your app through app stores like Google Play Store or Apple App Store, you typically use AOT-compiled code.
- JIT (Just-in-Time) Compilation:
- Purpose: JIT compilation is primarily used during the development and debugging phases of Flutter app development. It compiles Dart code into intermediate bytecode that can be executed by the Dart Virtual Machine (VM) during runtime.
- Performance: JIT-compiled Flutter apps may have slightly lower performance than AOT-compiled apps because of the intermediate compilation step during runtime.
- Start-up Time: JIT-compiled apps may have slightly slower start-up times compared to AOT-compiled apps because they require the Dart VM to compile code on-the-fly.
- Size: JIT-compiled apps have smaller binary sizes than AOT-compiled apps because they don’t include native machine code.
- Platform Compatibility: JIT compilation is platform-independent, making it suitable for development and debugging across different platforms from a single codebase.
- Example: When you use Flutter’s “hot reload” feature during development, you’re working with JIT-compiled code. It allows you to see code changes immediately without the need to recompile the entire app.
In summary, AOT (Ahead-of-Time) compilation is used for producing optimized, platform-specific release builds with better performance and faster start-up times. JIT (Just-in-Time) compilation is used during development for quicker iteration and debugging across multiple platforms. Flutter developers typically leverage both compilation modes during the development lifecycle to balance development speed and performance optimization.