Flutter is a free and open-source user interface software development kit. This toolkit includes its own rendering engine (Skia), many unit and integration testing APIs, plugin APIs, and command-line tools for building and compiling apps, it also has rich set of ready-made widgets in addition to a react-style framework.   The following is available inside the Flutter SDK, you can say any five of them. Dart SDK is a heavily optimized, mobile-first 2D rendering engine that has excellent support for text, it is a modern react-style framework for applications, and it uses APIs for unit and integration tests.   In this Interop and plugin APIs are used to connect to the system, and 3rd-party SDKs, and a headless test runner is used for running the tests on operating systems such as Windows, Linux, and Mac, the Dart DevTools available to us is used for testing, debugging, and profiling our developed application, Flutter and dart command-line tools are used for creating, building, testing, and compiling our applications, it also has a rich set of widgets that implement various Material Design and iOS styles.