When Satya Nadella became CEO of Microsoft in early 2014, he framed his strategy as “mobile-first, cloud-first.” In practical terms, that meant a heightened focus on cloud platforms such as Office 365, as well as the production of apps for Apple’s iOS and Google Android. (During the reign of his predecessors, cross-platform products would have been considered hearsay; how things can change in just a few years.) But what does that “mobile-first, cloud-first” strategy mean for Windows, the core of Microsoft’s software portfolio? According to Mary Jo Foley at ZDNet (as well as some people picking through Windows 10 software builds), Microsoft is planning something called “Windows Cloud.” What exactly is Windows Cloud? Mary Jo Foley’s sources suggest it’s a lightweight version of Windows 10 designed to run only Unified Windows Platform (UWP) apps from the Windows Store. For the uninitiated, UWP apps can run on a variety of devices, from smartphones all the way up to giant desktops, thanks to interoperability with Windows Runtime (WinRT), a common application architecture. In other words, it sounds like Windows Cloud will be similar in some ways to Chrome OS, Google’s lightweight operating system for Chromebooks. There are a lot of good reasons for Microsoft to consider a stripped-down operating system. First and foremost is competition: if more people turn to Chrome OS as a “good enough” operating system, it could end up threatening the Windows franchise. Second, it would give Microsoft more of a foothold in the market for cheaper and lower-powered machines. A few years ago, Microsoft tried something similar with Windows RT, a version of the operating system for tablets and hybrid devices based on ARM processors. That effort crashed and burned, largely because the reliance on ARM prevented Windows RT users from downloading and using apps built for “traditional” Windows, which is based on Intel architecture. It remains to be seen whether “Windows Cloud” or "Windows 10 Cloud," should it hit the market, suffers a similar fate because of its exclusive reliance on UWP apps and the Windows Store, which might limit its reach. Microsoft has struggled for years to convince third-party developers to build for the Windows Store, and, as the situation with Windows RT demonstrated, that lack of apps puts any new platform at something of a disadvantage right out of the gate, at least in comparison to the Android and iOS app stores. At the same time, Microsoft has to formulate some sort of response to Chrome OS, which is reportedly gaining popularity.