A web application framework developed by Microsoft to allow programmers to build dynamic websites, web applications, and web services. It was first released in January 2002 with version 1.0 of the .NET Framework and is the successor to Microsoft’s Active Server Pages (ASP) technology. ASP.NET is built on the Common Language Runtime (CLR), allowing programmers to write ASP.NET code using any supported .NET language. This provides a rich environment for building web applications with improved performance, security, and scalability compared to traditional ASP.