Just as Microsoft gets rid of one Windows SKU, it seems to have created another one to take its place. The short-lived Windows 10 S version has been replaced by a mode that can be applied to regular Windows, but it appears that there is already a successor: the latest Insider preview build for Redstone 5, due for release in the second half of this year, has an install option for "Windows 10 Lean," as found by Lucan.

Windows 10 Lean appears to live up to its name: an installation is about 2GB smaller than Windows 10 Pro, and it is missing a bunch of things, such as desktop wallpaper, Registry Editor, the MMC management console, and more. Lucan reports that Lean does not seem to apply the same restrictions as S Mode, and as such it is capable of running both Universal Windows Programs from the Store and traditional Win32 applications.

What's unclear is precisely who this Lean version is for. Saving disk space is certainly welcome, though on most PC-type devices, an extra 2GB isn't really going to make or break anything. It would be more important on a mobile device, but Lucan is certain that Windows 10 Lean is not some precursor to the operating system for the mythical Microsoft Andromeda device.

It also seems unlikely that "Lean" is going to be the final branding. While "Lean" is the name used during installation, the branding within the operating system is still "Windows 10 S." We'd expect this to change once the purpose becomes clearer.