An old build of Windows Core 'Polaris' has leaked online

WCOS Polaris Render
WCOS Polaris Render (Image credit: Windows Central)

What you need to know

  • An old build of Windows Core OS has leaked.
  • The leak is of a barebones Polaris SKU.
  • The build is for ARM32-based PCs only.

An early build of Polaris, a canceled SKU of Windows Core OS, has leaked online. The build is from early 2018, and includes nothing but the bare core OS, meaning there's no composer (shell) or apps present. Windows Core OS is a modern version of Windows that powers HoloLens 2 and the upcoming Windows 10X, and has been in the works for many years.

We've covered Windows Core OS extensively in the past, but for those out of the loop, the Windows Core OS project aims to create a modular, universal Windows OS that guts legacy features and components in favor of contemporary user experiences. As a result, the OS is more secure and performant on low-end hardware, with better battery life and faster OS updates.

Because Windows Core OS has been in the works for so long, the project has gone through many different phases internally. Originally, Windows Core OS was going to power the Surface Duo with the Andromeda SKU, as well as laptops and tablets with the Polaris SKU. Polaris was essentially Windows Core OS built specifically for PCs.

Polaris Registry Confirmed

Source: Windows Central (Image credit: Source: Windows Central)

Polaris was canceled right around the time Andromeda was canceled, as both SKUs were superseded by Windows 10X (codenamed Santorini). Polaris was going to replace Windows 10 S when ready as a true modern and lightweight version of Windows 10, featuring containerized Win32 programs but with the familiar Windows 10 desktop UX.

The build that has leaked is the RS3 RTM build, but as mentioned above, the actual leak includes very little for tinkerers to mess around with. It has no composer, meaning there's no GUI, and there doesn't appear to be any in-box apps either. This leak serves two purposes: confirms the existence of Polaris for those who doubted it, and allows enthusiasts to tinker with an old build of Windows Core OS.

Interestingly, the leak is also in the ARM32 architecture, meaning it can only boot on older ARM32-based PCs like the Surface RT. Once again, Polaris is a canceled edition of Windows Core OS and will never ship, so don't expect to see this on PCs in the future. Windows 10X is the future of Windows Core OS on PCs, and should begin shipping on devices later this spring.

Windows Central does not endorse or recommend downloading leaked builds of Windows. Do so at your own risk.

Zac Bowden
Senior Editor

Zac Bowden is a Senior Editor at Windows Central. Bringing you exclusive coverage into the world of Windows on PCs, tablets, phones, and more. Also an avid collector of rare Microsoft prototype devices! Keep in touch on Twitter and Threads