Why are const constructors important for Flutter performance?

When you use const constructors, Dart creates the widget object at compile time and canonicalizes it — meaning the same const widget with the same arguments is the exact same object in memory. Flutter's reconciliation algorithm can then detect that a const widget has not changed and skip rebuilding its entire subtree. This is a significant optimization in large widget trees where a parent setState() would otherwise force all child widgets to rebuild unnecessarily. Always use const for widgets that never change: const Text("Hello"), const SizedBox(height: 16).