Explain Flutter's 'everything is a widget' philosophy.

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Accepted Answer

Flutter's design philosophy: everything you see (and many things you don't) is a widget . Padding, alignment, themes, gesture detectors, navigators — all widgets. Three implications: Composition over inheritance — instead of subclassing a Button with 50 properties, you compose smaller widgets ( InkWell wrapping Container wrapping Text ) — each doing one thing well. The widget tree IS your app's structure — there's no hidden DOM, no separate styling layer. Anything reusable is a widget — layouts, themes, animations, even your MyApp class. Important nuance: Widgets are immutable, lightweight blueprints — they describe what the UI should look like. The actual rendered objects live in the Element and RenderObject trees (covered in the three-tree architecture question). The phrase to memorize: **'composition over inheritance'**. Flutter's design choice is that instead of a `Button` class with 50 styling properties, you compose: `InkWell( Container( padding, decoration, child: Text(...) ) )`. The right interview signal is showing you understand WHY: each widget does one thing well, and you wrap to add behavior. Mention that widgets are **immutable, lightweight blueprints** — not the actual rendered objects (that's the Element / RenderObject tree).