A web developer is responsible for designing, developing, and maintaining websites and web applications. They use programming languages such as HTML, CSS, JavaScript, and PHP to create interactive and responsive web pages that meet client requirements. A web developer also ensures that the website functions properly across different browsers and devices, and implements security measures to protect against potential threats. They may work in collaboration with designers, project managers, and other developers to create a seamless user experience. A web developer should have strong problem-solving skills, attention to detail, and the ability to work in a team environment.