A smaller, more pared down version of Windows 10 was spotted in the latest Redstone 5 preview build. Microsoft is calling it Windows 10 Lean and it's 2GB smaller in size than standard editions of Windows 10 once installed. Missing from this version are the Registry Editor, Internet Explorer, wallpaper, Microsoft Management Console and drivers for CD and DVD drives, and Windows Central notes that the lighter Windows 10 might be designed to ensure tablets and laptops with little internal storage can install Windows 10 feature updates.
Welcome to Windows 10 Lean/CloudE/S (once again?)— Lucan (@tfwboredom) April 20, 2018
This new edition started shipping with this week's Skip Ahead build (17650)
It seems to be heavily cut down, an x64 clean install is roughly 2 GB smaller than Pro
Its edition ID is 0xB7 which was missing from SDK headers pic.twitter.com/2Sn3SVXeZB
Additionally, the Redstone 5 preview also features phone-related APIs that support functions like dialing, blocking withheld numbers, video calling, Bluetooth headset support and speakerphone mode, stoking those persistent Andromeda rumors.
The Windows 10 Lean included in the preview build is buggy, according to Windows Central, and it's important to keep in mind that it's still in development. There's no guarantee about what Microsoft will choose to do with it going forward.