A front-end developer is responsible for creating and implementing the user interface and user experience of a website or web application. They work with HTML, CSS, and JavaScript to design and build responsive and visually appealing web pages. Front-end developers also collaborate with designers and back-end developers to ensure the functionality and aesthetics of a website are cohesive and user-friendly. They are essential for bringing the visual design and interactivity of a website to life, making it accessible to users across different devices and browsers.