If you try to create a folder with a leading dot, like the .well-known folder for domain validation or the security.txt, you may end up with the error “You must type a file name” on Windows Server:
If this happens, do not despair. There is a little trick you can use to create such a folder in Windows Explorer (the file manager): add a dot at the end.
Instead of creating a folder named .well-known you type .well-known. :
Windows Explorer will magically remove the ending dot and creates the folder with the name we want:
This little trick works with a wide range of Windows operating systems and goes way back.