What are “api-ms-win-*-*-lx-x-x.dll” umbrella libraries?

Question

I keep running into DLLs with long file names, as such. Just two for example: \"api-ms-win-appmodel-runtime-l1-1-1.dll\" or \"api-ms-win-appmodel-identity

Answer 1

this is “Virtual DLLs” names. loader, when we call LoadLibrary (LdrLoadDll) check for well known name prefix (say api- ) and if name begin with this - use ApiSetSchema mechanism for translate virtual dll name (i.e api-ms-win.. ) to real dll name (file name, like kernel32.dll, kernelbase.dll, etc). this mapping implemented in ApiSetSchema.dll which located in system32 folder.

about internal implementation - read Runtime DLL name resolution: ApiSetSchema - Part II and The API Set Schema