Before Windows XP, any application could open a file with a case-sensitive flag to request the operating system to not do any case folding. Starting with XP, the same feature exists but requires a registry key set (and a reboot) to instruct the kernel to allow case-sensitive operations.

Starting with Windows 10, the aforementioned key still works, but there's also a per-directory case-sensitive flag that forces all DOS and Windows programs to have case-sensitive operations unconditionally. This is made to great effect in both WSL1 and Cygwin.