Apache Flex

Apache Flex is an open-source framework used to create rich internet applications (RIAs) that can run on web browsers, desktops, and mobile devices. It allows developers to build visually engaging applications using a mix of programming and design elements, primarily using the ActionScript and MXML languages. Flex applications can deliver dynamic content and interactive user experiences similar to traditional desktop software but are accessible through web technologies. Although its popularity has waned with the rise of newer web technologies, it played a significant role in the development of web applications in the past.