Windows NTFS and case sensitivity

NTFS is a case sensitive file system and treats files with the same name, but different case, as different files.

The Windows API presents an abstraction of NTFS that makes it appear as a case preserving file system, and it does this via the CreateFile API that almost all file creation and opening requests are routed through.

Namely, the case sensitivity of file opening or creation is mediated by the FILE_FLAG_POSIX_SEMANTICS flag passed to CreateFile.

As Chris Becke said:

NTFS is a case sensitive file system and treats files with the same name, but different case, as different files.

Luckily, if you now want to have upper and lower case files, the new Windows 10 developers update allows you to enable that feature in certain folders, for development purposes. I just warn you that you shouldn't rely on that feature because older windows versions wouldn't support it and I don't know what could happen. Check out how to do it here: https://www.howtogeek.com/354220/how-to-enable-case-sensitive-folders-on-windows-10/