API Layering requires that binaries in Windows Driver packages call only those APIs and DDIs that are included in UWP-based editions of Windows 10 or are from a curated set of Win32 APIs. API Layering is an extension of the previous "U" requirement that was a part of DCHU design principles.
To see which platform an API supports, visit the documentation page for the API and examine the Target Platform entry of the Requirements section. Windows Drivers must only use APIs or DDIs that have a Target Platform listed as
Universal, meaning the subset of functionality that is available on all Windows offerings.
The Windows API Sets page describes a set of best practices and tools for determining whether an API is available on a particular platform.
Validating API Layering
ApiValidator is the main tool used to validate API Layering compliance for Windows Drivers. ApiValidator ships as part of the Windows Driver Kit (WDK).
See Validating Windows Drivers for more details on using ApiValidator to verify that a Windows Driver meets the API Layering requirement.