i dont know if it still work with webext .. but maybe you could use unsafeWindow instead of window to tap into the controlls for other players

God Bless you! It! Wonderful - so many videos I like are so low I can't hear them at all. This really, really works! Yay!

It actually does what the description says !
5 stars from me and keep up the good work ! :)

Works for Youtube and Netflix!

Finally, I can crank up the sound on movies that are too quiet for my laptop speakers!

Давно мечтал о таком расширении

Works awesome!

It should be built into the browser.

Is it possible to move the button to the address bar and show only when audio is playing in the current tab? I'd prefer that behavior over the ever present toolbar clutter.

Fixed the issues I had on youtube audio, I only heard the left channel bu this fixed it.

Works well on YouTube. Thank you.

It works beautifully! With so much crap that YouTube developers exchange, and that we don't want, they don't bother to resolve the volume problem! This add-on does just that, it solves the problem! Thank you very much!

очень полезно для тихих роликов

Noticed the difference, could see the difference!

It's great!
Before finding this extension I used to have trouble hearing some YouTube videos at full volume. Now using this extension I don't even have to change the volume to hear the videos, just adjust the top slider. Also I love how it resets each time so everywhere else I go isn't too loud.

It's working well.Thank you!

Some youtube videos or livestreams volumes are too low. With this I don't have to turn up my receiver all the way up.

Love this add-on. Facebook messenger always blasts my ears but now whether it's that or youtube videos playing back at high decibels, I can lower it to my liking.

Please add vk.com support for music. It's so annoying.

Очень полезное дополнение. Для тихих роликов - самое то.

Wonderful audio boost for web audio, very very thankful to developer for very useful app. 5 Star.
I request to developer; please increase the volume gain a little more in the extension script.Thus we can more boost, this is not harmful to speaker because the main volume control is in our hand so we can adjust at desired level. Regards

I was looking to increase the volume of a video I was watching. With SoundFixer, I didn't need to plug in my speakers!
Great job guys and thank you!