WinFX is the programming model for the Windows "Longhorn" operating system.

WinFX is to Longhorn what Win32 is to Windows XP and Windows Server 2000/2003. However, unlike Win32, WinFX is a managed API. As a result, only managed applications will be able to take full advantage of WinFX: using COMCallableWrappers will not be particularly attractive as they imply constant costly transitions between managed and unmanaged code. So the first step on any RoadToLonghorn is to move to managed code in the .NET Framework.

Some or all of WinFX will be back-ported to Windows XP and Windows Server 2003, but not Windows Server 2000 due to security reasons.

The WinFXMarch2005CTP contains both Avalon and Indigo SDKs, and runs on Window XP SP2 and Windows Server 2003. It is available for public download