A Framer developer uses the Framer prototyping tool to create interactive and responsive designs for mobile and web applications. They design layouts, animations, and interactions using Framer's visual design tool, and write code to customize functionality and behavior. They also test and debug these designs, ensuring an optimal user experience. Framer developers often work closely with UX/UI designers and developers, translating design ideas into workable prototypes. They may also conduct usability tests, analyze user feedback, and implement changes to improve the design. Their goal is to create engaging, intuitive, and user-friendly interfaces.