Flutter is an open-source UI software development toolkit created by Google for building natively compiled applications for mobile, web, and desktop from a single codebase.

Ionic is an open-source framework for building cross-platform mobile applications using web technologies such as HTML, CSS, and JavaScript/TypeScript.

React Native allows developers to use a single codebase to create native-like experiences for both iOS and Android platforms.

Xamarin enables the creation of apps for iOS, Android, and Windows with a shared codebase, providing a balance between code reusability and platform-specific optimizations.