https://www.theverge.com/2018/4/25/17279042/microsoft-windows-10-lean-edition

Microsoft’s next version of Window 10, currently codenamed Redstone 5, will include a new “Lean edition” designed for devices with less storage space. Sources familiar with Microsoft’s plans tell The Verge that the new edition will be offered to OEMs to load onto low-cost laptops and tablets. Windows Central first reported that the edition will be available for devices with 16GB of storage, and it’s primarily designed to ensure these machines still receive Windows updates.

Twitter user Lucan discovered references to the Lean edition in the latest publicly released Windows 10 test build (17650), and at the moment the install cuts around 2GB of storage space. Microsoft is reducing the storage space needs by removing components that won’t typically be needed on these low-end devices, like Internet Explorer and other legacy desktop apps. Even regedit has been removed, and Microsoft is experimenting with removing as much as possible.