A support document for Windows 10 version 1903 mentions Windows Core OS several times. Microsoft has never officially mentioned Windows Core OS in a statement or announcement, even though the operating system will power two devices that have already been shown off, the HoloLens 2 and the Surface Hub 2. Windows Latest spotted that a support document for Windows 10 version 1903 mentions Windows Core OS specifically.

The support document was published in April of this year but was only spotted recently. The document states that it takes 274 minutes to read and is one of many support documents from Microsoft, so it's not surprising that a few short mentions of Windows Core OS went unspotted for months.

The document is for basic level Windows diagnostic events and field for Windows 10. Underneath the subheading "Common Data Extensions.utc" the document lists three items related to Windows Core OS:

wcmp The Windows Shell Composer ID.

wPId The Windows Core OS product ID.

wsId The Windows Core OS session ID.

As pointed out by Windows Latest, Github shows that the mentions of Windows Core OS were added April 19, 2019.

Windows Core OS is a version of Windows with a universal base that can work across different devices. There are several "flavors" of Windows Core OS including versions for laptops and foldable PCs, collaborative displays such as the Surface Hub 2, and Windows Mixed Reality devices like the HoloLens 2.

How to watch the Microsoft Surface event live stream on October 2

Our Senior Editor, Zac Bowden, created an extensive breakdown of Windows Core OS, including explaining several related components like CShell. There's a chance that a variant of Windows Core OS will be mentioned or shown off at the Surface event on October 2, 2019.