URL
A URL string. If no default value is specified, a URL type defaults to an empty string. URLs are not delimited (i.e. quotes are not required).
URL attributes behave like string attributes. When displayed in a text window's key attributes table, URL attributes titles have a button like the sidebar $URL's 'View In Browser' button; pressing the button opens that attributes stored URL (if any) in your default web browser.
Links dropped on a URL-type key attribute populate that attribute; links dropped on any other data type key attribute populate the system $URL.