For the last several months, we've been talking about an internal project ongoing at Microsoft, codenamed "Windows Lite" which is a new version of Windows powered by Windows Core OS and built from the ground up as a modern platform for new devices. This is the version of Windows that will run on foldable PCs and lightweight computing devices, which will tackle the iPad and Chrome OS head on. For a while, it was believed that Microsoft would take the wraps off Windows Lite at its Build 2019 developer conference in May, as that's arguably the place where announcing a new version of Windows makes the most sense. Microsoft announced Windows 8 at Build, for example.

'Windows Lite' a no-show at Build

Unfortunately, it sounds like that won't be happening. I've been told by people familiar with the matter that Microsoft will not use Build 2019 as a stage for Windows Lite, as it's just not ready yet, and Microsoft doesn't want to take away from all the other developer-orientated announcements related to Microsoft Azure and Microsoft 365. A Windows Lite announcement at Build would dominate headlines. So with Lite not happening at Build, when can we expect to see Microsoft announce it?

Windows Lite would be a bad name for Microsoft's upcoming OS

The timeline for Windows Lite is ever-changing, so it's hard to nail down an exact timeframe for when it will be officially announced. There are several different milestones Microsoft wants to reach internally before an announcement is even considered. For example, Microsoft is currently working hard on getting the new Chromium version of Edge to run on Windows Lite. Right now, it doesn't run because the work required to get Win32 programs running on Windows Core OS isn't yet complete.

I wouldn't be surprised if Microsoft Edge moving to Chromium has thrown a bit of a wrench into things regarding Windows Lite. From the very beginning, Windows Lite and the old Microsoft Edge have been tied at the hip. Things like Windows Sets and the old Edge played a critical role in the overall Windows Lite experience. But, now that the old Edge is going away, and Microsoft is moving entirely to the new Chromium version of Edge, some things regarding Windows Lite must adapt.

When will Microsoft announce Windows Lite?

I hear Microsoft wants Windows Lite to go into broader internal testing sometime this summer. It's likely that by then, the new Microsoft Edge will be up and running on Windows Lite. So, realistically, the earliest we could expect to see Microsoft announce Windows Lite is sometime this fall. But even then that's not guaranteed, because Windows Lite isn't scheduled to start shipping on devices until sometime in 2020 at the earliest. It all depends on whether Microsoft is planning a public preview for Windows Lite before it starts shipping.

Windows Lite is a new version of Windows that's locked down. As far as I know, you won't be able to simply install it on whatever devices you like. Internally, Microsoft uses the Full Flash Update format (FFU) to load Windows Lite onto devices, not ISOs, which are used for installing Windows onto devices today. So, Microsoft would have to create an FFU for whatever device it wants to test Windows Lite on. Internally, I know Microsoft is currently testing Windows Lite on the Surface Go, and Surface Pro 4, 5, and 6.

An announcement in the fall would only make sense if Microsoft were planning to release preview builds. Otherwise, it'd make much more sense to announce it in 2020, alongside hero devices like "Centaurus" that are supposed to ship with Windows Lite. There's very little reason to announce a new version of Windows several months or a year before people can get their hands on it, in preview form or otherwise.

Either way, work on Windows Lite is still ongoing. And, put simply, Microsoft needs this OS to succeed.