Firefox will "mix" audio streams when multiple videos are running at the same time.

There are settings in Firefox / extensions you cal install in Firefox to not automatically launch videos when the page loads; "click to play".

the-edmeister-3; thank you. When I go to "tools, add-ons, extensions" I don't see any items of that type. Can you provide more information?

Sorry, I just live with it and mute the videos when I accidentally get more than one running at the same time. I use the Flash Control extension to keep both Flash and HTML5 videos from automatically running when the page loads, but I'm not sure if that extension is compatible with Firefox 53. I stuck with Firefox 47.0 for the Profile that I use with general surfing and watching YouTube videos; got damn tired of one or two of my extensions breaking for good with every damn Firefox update. And I intend to hold fast for that Profile, until after Firefox 57 is released when almost every extension I use will "break" - then I'll either come up with alternative extensions or switch to a different browser. If I would happen to "pick up" something that my AV misses due to using an older version of Firefox, so be it - I will become a former internet user. Good way to "knock the monkey off my back" - addiction to the internet, that is.

Positive note, I am so thoroughly disgusted with the recent changes in Firefox, and those coming down the pike that I am wasting less of my time on the internet and reading more books. But I still haven't beaten the "Pavlov's response" when I see a TV ad about computers or see one being used in a TV program, where I compulsively walk across the room at the next commercial break and wake up my PC and do "something" - anything. I almost wish my response to that type of stimulus was drooling instead - LOL.

I just took a peek at my Firefox 53.0.3 installation - as far as a "setting" in about:config try toggling this preference dom.audiochannel.mutedByDefault to True.

Hi   halben   !

Would you do this, please :

Type in the address bar   about:config   (press Enter) (promise to be careful, if asked) Type and look for the preference : media.autoplay.enabled and make sure it's value is set to   false

And maybe you'd like to give this add-on a try   (works perfectly with the above mentioned pref) :

https://addons.mozilla.org/en-US/firefox/addon/flashstopper/