A development build of Windows Core Polaris was leaked online yesterday, proving that Microsoft was actively developing the operating system designed for low-performance devices.

For those unaware, Microsoft has been secretly working on a modular version of the Windows platform codenamed “Windows Core OS.” With Windows Core OS, Microsoft planned to offer different flavors/SKUs of Windows for various form factors, such as phones, 2-in-1s, dual-screen PCs, and collaboration devices.

Using Windows Core OS, Microsoft initially created two flavors of Windows – Andromeda for mobile devices and Polaris for traditional laptops.

Polaris was built for low-end devices, and it was supposed to replace Windows 10 in S Mode to take Microsoft’s concept of a Store-restricted operating system one step further. Polaris is also thought to be Microsoft’s first attempt to remove all the legacy elements of Windows, such as the Control Panel.

Polaris leaks online

An old Microsoft Polaris build 16299 from 2018 was leaked online yesterday, but without a Windows shell or apps.

“This is PolarisOS. It’s a cancelled edition of Windows Core OS that was designed for Desktops and Laptops. This image is early enough to not include much more than the OS itself. It comes with no shell, and won’t load any.”

“You need an ARM device to boot this, and you need to sideload drivers before first boot. The wim is bootable, but you can also install it directly by applying index 1,” the leaker known as Scamdisk stated in the leak.

This build dates backto  2018, when Microsoft shifted its focus to Windows Lite/Santorini (now known as Windows 10X).

The leaker, Scamdisk, has a history of leaking confidential builds of different Windows versions. In the past, Scamdisk released confidential builds of Windows 7. Windows 8, Windows 10, and Windows Server.

Windows Core OS: Polaris, Andromeda and 10X

Microsoft canceled Polaris after they started working on a new SKU of Windows Core OS called “Windows 10X.”

Like Polaris, Microsoft has also canceled Andromeda OS, a small screen optimized version of Windows Core OS for mobile devices, such as the Surface Duo and HP Elite x3.

Microsoft has swapped out Andromeda OS with Android on its Surface Duo, and Polaris has now been succeeded by Windows 10X, another Windows Core OS-powered operating system that would work on any form factor.

Windows 10X is expected to launch later this Spring, and it will be aimed more towards casual users with a new UWP version of the File Explorer and static Start Menu that would make navigation easier for those who don’t like live tiles.