Platform-agnosticism is a relative measure of how an app works the same way, irrespective of the operating system on which the app is running.

Flutter is platform-agnostic because it gives users of Flutter-built apps the same experience across their different devices. Flutter is platform-agnostic through how it renders user interfaces and through platform channels.

For UI, Flutter's rendering uses multiple layers. Also, Flutter grabs a blank canvas on the target platform and paints as it likes. In addition, the same Flutter engine is shipped in every app so Flutter paints the Dart code in exactly the same way.

For Platform Channels, Dart (the flutter side) can call methods and listen to events whose declarations are found in the native side (of the target platform) and vice versa. This enables plugin development and streamlines native features in the Flutter app.

In this session, the audience will understand the crucial benefits of platform-agnosticism especially in this our modern times of the sovereignty of cross-platform tools. Furthermore, session participants will appreciate how Flutter achieves this fit of being platform-agnostic through rendering UI and using platform-channels.

We will walk through how a host/native app is different from the "inner" Flutter app and engine. We will also see how Dart's Binary Messenger serializes/deserializes function calls across both sides. Finally, the audience will grasp the difference with Flutter's execution on the Web as browsers are not Operating Systems.