Web developers build and maintain websites and web applications, using programming, design tools, and languages such as HTML, CSS, Python and JavaScript to meet both client and end-user needs.A web developer is a programmer who develops World Wide Web applications using a client–server model. The applications typically use HTML, CSS and JavaScript in the client, PHP, ASP.NET (C#), Python, Node.js, Go or Java in the server, and http for communications between client and server. A web developer may specialize in client-side applications (front-end developer), server-side applications (back-end developer), or both (full-stack developer).