Appetize.io is a platform that offers a web-based simulator for running native mobile apps in the browser. It supports both iOS and Android applications, enabling developers to test and showcase their mobile projects without the need for physical devices. The platform provides a range of features including easy integration with development workflows, support for automation and CI/CD processes, and the ability to share app demos via email or embedded links. Appetize.io is particularly useful for developers, testers, and marketers who need accessible and flexible app testing solutions.