It does stop Youtube videos from auto-loading and playing when I open them in a new Tab.
I noticed that when i open, for e.g., a CNN news page (that has an embedded video in a new Tab) - but without actually going to that Tab - the video will not auto-load or play. But the moment I click on the Tab to view the news, the video automatically starts loading and playing.
It would be nice if the add-on can stop this auto-loading and playing until the play button is physically clicked (this will help the lot of us who are on a limited monthly data subscription).
Currently running Firefox 57.0 64Bit (updated Nov 17 2017).
