A web applications developer designs, creates, and modifies web-based applications. They use programming languages such as HTML, CSS, JavaScript, and server-side languages like PHP or Python to build interactive websites or web services. Their responsibilities include writing well-designed, efficient code, integrating data from various back-end services and databases, gathering and refining specifications and requirements based on technical needs, creating and maintaining software documentation, and ensuring high-performance and responsiveness to requests from the front-end. They often work in cross-functional teams, collaborating with UX designers, business analysts, and other IT professionals.