ASP.NET is primarily a backend framework. It is used to create the server-side logic of a web application, including handling HTTP requests, performing operations on a database, and dynamically generating HTML to be sent to the client. However, ASP.NET can also be used to generate the HTML, CSS, and JavaScript that runs in the user's browser, which is typically considered the frontend. In many cases, though, ASP.NET is used in conjunction with frontend frameworks or libraries like Angular, React, or Vue.js to create a complete web application.