I am unable to stream YouTube videos using the Apple iPhone or iPad via the ProxySG when authentication has been configured.
YouTube streaming video on the iPhone or iPad utilizes a built in application which has no capability to automatically send a credential or login prompt. However, there are several ways to enable functionality for the iPhone and iPad devices:
<Proxy>
request.header.User-Agent="iphone" authenticate(no)
The above resolution will work as long as there is no rule to Deny access to the youtube.com domain. If you need to allow only certain youtube.com video while blocking the rest, refer to 000007861.