A Web application (or webapp) is an application which is accessed via a Web over a network such as the Internet or an intranet.

Web applications are popular due to the ubiquity of a client, sometimes called a thin client. The ability to update and maintain Web applications without distributing and installing software on potentially thousands of client computers is a key reason for their popularity.

Though many variations are possible, a Web application is commonly structured as a three-tiered application consisting of a Web browser, ASP.NET as the middle tier, and a database as the third tier.