hot reload

Inject updated source code directly into a running virtual machine to instantly preview UI changes without losing application state.

Hot reload bypasses the traditional, time-consuming cycle of rebuilding and restarting an application after every minor code edit. By injecting updated source files directly into the running Dart Virtual Machine or runtime engine, it updates the widget tree and UI elements in milliseconds (often under 300ms) while fully preserving the application's current state. Developers can tweak layouts, fix bugs, and experiment with UI designs on the fly, keeping their exact place in the user flow without having to navigate back through login screens or nested menus.

https://docs.flutter.dev/tools/hot-reload