Proxying an external URL using browser sync

[shantiswarooppreddy]

Hi,
As a tester I would like to test a given website hosted on an external server using browser sync on multiple browsers. When I try to access the URL using the command browser-sync start --proxy "any external URL" the link is opened in a web browser but it does appear to be synced with browser sync. Is it actually possible to test an external website on multiple browsers using browser sync. And if so how ?

Thanks,
Swaroop