What is Microsoft's Windows Core OS 'Lite'?

Microsoft allegedly is going to try (yet again) to take on ChromeOS with a locked-down Windows 'Lite' platform. Here's what I think could be in the works.
Written by Mary Jo Foley, Senior Contributing Editor

Despite numerous leaks (which have appeared on this blog and elsewhere) about Windows Core OS, a k a WCOS, Microsoft never has publicly explained this terminology. In part, this may be the result of the constantly evolving nature of WCOS. And based on a new report out today, it looks like there may be yet another new WCOS wrinkle.

WCOS is, in a nutshell, is the successor to Windows OneCore -- Microsoft's strategy to modularize Windows and create a shared kernel and dev platform that would enable the foundation of Windows 10 to be shared across devices, based on what I've heard from my sources.

Like Windows Central and others, I've been hearing that Microsoft was working to modularize Windows 10 further and create WCOS and a bunch of different shells (like Aruba, Sydney, Scarlett, Polaris, Andromeda and others) to work on different form factors. This was the plan of record up until earlier this year.

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Once Windows Chief Terry Myerson left, however, it sounded from my contacts like everything was in flux regarding the best way to move Windows forward.

Even though subsequent Windows 10 software development kits contained references to WCOS and Andromeda, Microsoft shelved, at least temporarily, plans to release a dual-screen, phone-sized Andromeda device. (One thing to keep in mind in all these codename discussions is that "Andromeda," confusingly, is a codename for both a hardware device and a software shell. In this case, I'm talking about Andromeda the device.)

WCOS, however, lived on as the operating system for future Windows devices.

According to my contacts, however, a priority for WCOS shifted: Instead of being a Universal Windows Platform (UWP) only platform, as it was originally designed, Microsoft officials decided to allow WCOS to run Win32 apps.

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This is where the notion of Windows "Lite" comes in, I believe. I think Lite is going to be a restricted version of WCOS.

Credit: Tero Alhonen on Twitter

Last week, Tero Alhonen posted a list of what looked to be different Windows SKUs, or editions, that were listed in a recent Windows 10 SDK build. On that list, in addition to Cloud (which was the codename for Windows 10 S) and Andromeda was something called "Lite."

Today, on Petri.com, Brad Sams reported that this Lite SKU might be yet another attempt by Microsoft to take on ChromeOS with a restricted version of Windows 10. Sams says, like Windows 10 in S Mode, Windows Lite might be restricted to UWP/Store applications. He also reported that Microsoft might opt to name this SKU something other than "Windows."

The reason for this possible name/branding change makes sense to me. A number of customers who have purchased the very few PCs that shipped with Windows 10 in S Mode on by default have been confused by this variant. Windows 10 in S Mode looks like Windows and seems to run Windows apps. But it hasn't been all that clear that S Mode only lets users run a subset (UWP/Store) apps only and not all Win32 apps.

Right now, the only Surface device that Microsoft sells running Windows 10 in S Mode out of the box is Surface Go, the low-end portable Surface devices introduced this year which are targeted at the education, consumer and firstline-worker segments. Microsoft no longer makes Windows 10 in S Mode the default OS on Surface Laptop, as it did initially when the first version of that product shipped.

Microsoft hasn't completely axed Windows 10 in S Mode -- it's still available for customers who want its purported extra security and performance -- but it would be tough to characterize S Mode as a success (regardless of the telemetry methods used), I'd feel safe saying.

The biggest question I still have about WCOS is how it will work under the covers. Will it work like Microsoft's "Continuum" experience, in that plugging a WCOS device into a larger screen and keyboard will give users a full desktop-type experience? Will it use virtualization in some way, so that all WCOS applications run in a virtual machine hosted remotely? Will WCOS restrict applications so that Win32 apps run in a VM? I've heard from my sources that all of these ideas have been on the table at various points. I'm not sure which, if any, of these options has emerged as the "final" choice.

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While I believe any brand-new Surface device types will run WCOS inside, I don't know which ones will run WCOS Lite. Some are speculating that whatever succeeds Andromeda might be a candidate for WCOS Lite. I haven't heard from any of my sources which devices Microsoft believes would be suited for such an OS.

Because of the still relatively small number of quality UWP/Store applications -- something that MSIX and Progressive Web Apps might help change at some point -- it's hard to see any new device shipping in the near-term being a potentially successful WCOS Lite platform.

Microsoft isn't commenting on Windows Lite or WCOS Lite. This post is just me taking info from sources and trying to connect the dots....

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