A frontend developer is responsible for creating the visual elements of a website or application that users interact with. They work on the client side of web development and use their knowledge of HTML, CSS, and JavaScript to create responsive, user-friendly interfaces. Frontend developers are also responsible for optimizing websites and applications for speed, ensuring cross-browser compatibility, and implementing best practices for accessibility and user experience. They often work closely with designers, project managers, and backend developers to ensure that the finished product meets the needs of both clients and end users.