A Cross-Platform developer designs and builds applications that operate seamlessly across different operating systems like Windows, Mac, Linux, iOS, and Android. They use various cross-platform frameworks such as React Native, Flutter, Xamarin, among others. Their responsibilities include writing clean and efficient code, fixing bugs, ensuring the application's performance and responsiveness, and integrating user-facing elements with server-side logic. They also work on upgrading, improving, and customizing existing systems. Furthermore, they work closely with other team members, including UI/UX designers and quality assurance testers, to deliver high-quality applications.