Play video in many website always with 100% volume. This edd-on resolves my problem.

Just what Firefox needed don't want to wake the family when playing a video early in the morning or late at night while they are all in bed. Firefox always defaults audio to 100% but this you can set to what volume you like and it stays that way brilliant thank you..

很棒很直接的插件，直接解決了我影片聲音太小的問題

Genau richtig um die Webseiten leise zu halten , Danke

Simply good. This extension does what it stands for: it globally overrides volume control across all pages with HTML5 video.
It's a good news when you're trying to amp up your tumblr dashboard but this causes all other pages to change volume too. So Youtube volume controls being completely useless while this addon is active.

I hope there is a way to implement whitelisting/blacklisting feature or even dashboard to manage volume settings per-domain and author will consider doing that.