Microsoft froze the .NET Framework in 2019, yet Windows still ships it
The .NET Framework powered a generation of Windows software, letting code written in one language call code from another inside a virtual machine. Microsoft stopped adding features after version 4.8 in April 2019, but the framework still comes bundled with Windows and still gets security patches, with no plan to remove it as of July 2025.
Work began in the late 1990s under the name Next Generation Windows Services, and the first betas of version 1.0 appeared by early 2000. The idea was a managed environment: programs run inside the Common Language Runtime, an application virtual machine, rather than directly on the hardware. A huge shared library, the Framework Class Library, handles interfaces, databases, cryptography, web apps, maths and networking, so developers combine their own code with ready-made parts, typically inside Microsoft's Visual Studio. Windows Vista was the first desktop version of Windows to include the framework built in.
Microsoft moved to standardise the core surprisingly early. In August 2000 it teamed up with Intel on the Common Language Infrastructure and the C# language, both ratified by ECMA in December 2001 and by ISO in April 2003. Those bodies require essential patents to be licensed on reasonable, non-discriminatory terms, and the companies promised royalty-free access. The catch was that big pieces, such as Windows Forms, ADO.NET and ASP.NET, lay outside the standards, and Microsoft's patents there may have discouraged anyone building a complete rival version.
Open-source developers remained uneasy, especially about patents. Microsoft edged toward openness in stages. In October 2007 it said the source for the version 3.5 libraries would be published under its Reference Source License, and the code went online on 16 January 2008, covering areas like WPF and XML. Over time the company reshaped .NET development to look more like a community project and updated its patent promise.
Side branches stretched the platform to small devices: the Compact and Micro editions targeted Windows Mobile, Windows CE and embedded hardware, while Silverlight brought it into browsers via plug-ins. In the end the proprietary framework was overtaken by the cross-platform .NET project. Version 4.8.1 followed in August 2022, and since then only monthly security and reliability fixes have appeared.
Source: .NET Framework
