ASP.NET is a server-side web-application framework designed for web development to produce dynamic web pages. It was developed by Microsoft to allow programmers to build dynamic web sites, applications and services. The name stands for Active Server Pages Network Enabled Technologies.^{[citation needed]}

ASP.NET was first announced to the public under the codename ASP+, and is a re-implementation of 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. The ASP.NET SOAP extension framework allows ASP.NET components to process SOAP messages.

In 2016, Microsoft released ASP.NET Core as ASP.NET's successor. This new version is a re-implementation of ASP.NET as a modular web framework, together with other frameworks like Entity Framework. The new framework uses the new open-source .NET Compiler Platform (codename "Roslyn") and is cross platform. ASP.NET MVC, ASP.NET Web API, and ASP.NET Web Pages (a platform using only Razor pages) have merged into a unified MVC (model–view–controller) 6.

ASP.NET supports a number of programming models for building web applications:

Other ASP.NET extensions include:

On IIS 6.0 and lower, pages written using different versions of the ASP framework cannot share session state without the use of third-party libraries. This does not apply to ASP.NET and ASP applications running side by side on IIS 7. With IIS 7.0, modules may be run in an integrated pipeline that allows modules written in any language to be executed for any request.

It is not essential to use the standard Web forms development model when developing with ASP.NET. Noteworthy frameworks designed for the platform include:

ASP.NET's release history tightly correlates with the .NET Framework releases: