Windows Core OS

Windows Core OS (abbreviated as WCOS) is an internal Microsoft effort that aims to provide a universal, modular base for future versions of Microsoft Windows. The operating system is still based on the NT kernel, although most legacy features found in regular desktop Windows have been stripped out. Instead of the traditional Windows Explorer shell, the platform uses a newly built GUI stack based on DirectX and the UWP/WinUI frameworks. By default, WCOS variants are not natively compatible with applications using the legacy User and GDI libraries for their user interface, however, they can run virtualized using either remoting or a purpose-built container.

The introduction of a common core for all Windows-based products has been planned back as early as 2002. However, actual work would not start until 2014 with OneCore, which unified all products previously using separate forks of the Windows codebase into a single source code repository, enabling everything to be built from a single codebase although each product still provided its own shell on top of the common core. Windows Core OS is a natural extension of this effort, as it provides a common modular shell which can be customized for individual needs of each product.

List of flavors

Windows 10X (Centaurus/ModernPC CDG)

Originally intended for dual-screen devices, later redesigned for single-screen devices as a competitor to ChromeOS. Canceled shortly before release in favor of integrating key technologies to existing products.

Windows Core

Internal test flavor intended for operating system base layer and component testing.

Andromeda OS

Intended for use on the Surface Duo device family (codenamed Andromeda). Canceled in favor of Android for the Surface Duo 1 (codenamed Epsilon).

Polaris OS

Canceled flavor with a desktop-like user interface.

Factory OS

Lightweight version intended for use on factory floor and driver development.

Aruba OS/Hub OS/Modern PC LSX

Intended for use on the canceled Surface Hub 2X. Canceled in favor of maintaining a single version of Surface Hub (Surface Hub 2S) running on Windows Team (PPIPro) or Windows Desktop editions.

Windows Holographic (Oasis)

HoloLens 2 firmware. Does not make use of CShell Composers and instead uses its own shell.