Why should you create a folder starting with a dot?

Few days ago I was buying an SSL certificate for a web site, for which I had to prove that I really was the owner.

One way to do this was create a well known folder in the website with a name indicated by the provider and put a special file there.

Unfortunately the name of the folder contained an initial dot, and when I tried to create the folder I received the error message: “You must type a file name”, which you can see in the following screenshot:

It turned out that to overcome the problem I had to create the folder through the Windows command prompt using the following command:

md .MyNewFolder

The problem described above happened in a Windows Server 2019 machine. Curiously, I was able to create the folder through the user interface in my Windows 10 desktop.

Mysteries of computer sciences… 😉