How to validate if url exist

Hello,

Is there any way to check if the url exist?  I used download tool to check it.  Some site successfully works by looking at Download Headers.  When the Download Headers says "HTTP/1.1 200 OK", I know that the url exist.  However, some site always says "HTTP/1.1 999 Request denied".  Is that because it is private website?

I attached a sample workflow.

Sincerely,

Kazumi