Indigo and Avalon are the codenames for two strategic developer technologies that Microsoft plans to ship in 2006 as part of the Windows "Longhorn" operating system. In addition, Microsoft is making these technologies available on Windows XP and Windows Server 2003. The Indigo and Avalon Community Technology Preview (CTP) enables developers to experiment with early builds of these technologies, get acquainted with the development experience, and provide Microsoft with feedback. This CTP release recently became available to MSDN subscribers and is now being released to the general public in response to numerous requests.

Indigo is the codename for Microsoft’s unified programming model for building connected systems. It extends the .NET Framework 2.0 with additional APIs for building secure, reliable, transacted Web services that interoperate with non-Microsoft platforms and integrate with existing investments. By combining the functionality of existing Microsoft distributed application technologies (ASMX, .NET Remoting, .NET Enterprise Services, Web Services Enhancements, and System.Messaging), Indigo delivers a single development framework that improves developer productivity and reduces organizations’ time to market.

Avalon is the code name for Microsoft's unified presentation subsystem for Windows. It consists of a display engine and a managed-code framework. Avalon unifies how Windows creates, displays, and manipulates documents, media, and user interface. This enables developers and designers to create visually-stunning, differentiated user experiences that improve customer connection. When delivered, Avalon will become Microsoft's strategic user interface (UI) technology.