Async just means that there is a script, which, some time after the page is technically "fully loaded", starts to load some more! That's useful for updates or a

Async just means that there is a script, which, some time after the page is technically "fully loaded", starts to load some more! That's useful for updates or actions that should occur without a complete page reload (which would discard the "user state"). It doesn't necessarily mean you see an URL list. It can be implemented by storing the list in Javascript code - and you don't "see" that Javascript code. The method you mention (mis)uses HTML Tags as datastore for the URLs list.