Re:Everyone can now track down noisy tabs
by mbrubeck on Wednesday January 15, 2014 @12:11AM
(#7061774)
In Firefox, the "media.autoplay.enabled" pref can be used to disable the "autoplay" attribute for the <video> element. (But I think it may still be possible for pages to auto-start videos using JavaScript.)
Unfortunately, I don't know how to stop HTML5 videos from auto-playing.