Good question. Most stuff I find is archived , older browsers and does not work for you. See if anything works here : https://support.mozilla.org/en-US/kb/html5-audio-and-video-firefox and https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues Note if a website has both Flash and Html5 the browser chooses. Which one I have no idea.

There is a Extension for html5 volume control here: https://addons.mozilla.org/en-US/firefox/addon/html5-video-everywhere/

Please let us know if this solved your issue or if need further assistance.

Take a look at the volume mixer when that happens. There is a Bug (which is fixed for Firefox 57) where when multiple Firefox processes appear in the volume mixer they will all revert to 100% volume. How the hell that Bug ever made it thru Beta testing is beyond my understanding, but it is fixed in the next release version - not considered important enough to create a "chemspill'" release for Firefox 56.0.

did more testing and seem that the volume going to max just happens on boot up of Firefox with out of any video or music playing.

tried out (Pkshadow) suggestion of "html5 everywhere" plugin and this finally fixes the volume problems but in order to fix the problem is to download a plugin is an absolute fail on mozillas part...

well i guess i will upgrade to Firefox Quantum when that comes out :\

Yes it is.

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily. Thank you for contacting Mozilla Support.

sorry i have spoken too soon, the problem is still there and turns out the plugin html5 everywhere did nothing at all despite how many settings i turn on or off.

seems like i just have to wait for Firefox Quantum

the-edmeister said

(which is fixed for Firefox 57)

Well, I,m using Firefox 57 beta (10 at the moment) and experiencing the same problem since the beginning (about 5 or 6 beta). Here is a screenshot of Win mixer. "Mozilla Firefox" — the item, that always there, and the second one "Firefox" — appears with every new tab with audio, i mean, if I open 10 Youtube tabs, there will be 10 "Firefox" item in the mixer, which I can adjust individually.

This might only work if there are separate content processes for each of the tabs that have a media player. Once you reach the maximum number of content processes then this may no longer work.

• "Options/Preferences -> General -> Performance" (dom.ipc.processCount)

You can look in "Help -> Troubleshooting Information" (about:support) to see the current multi-process state.

• "Help -> Troubleshooting Information" -> "Application Basics":
  Multiprocess Windows
  Web Content Processes

Multi-process option is disabled in my case. «dom.ipc.processCount» = 1.

This isn't fixed in the 57 release. Still does it, seems to reset for every tab.

I still have this same problem as well, running the newly updated Firefox 57.0.2 (problem started after updating to 57). Windows 7 64-bit.

Every time I either open a new Tab in Firefox, or close/re-open Firefox completely, the sound levels for Firefox in the Windows Volume Mixer ALWAYS reset to 100%. This is VERY TIRESOME to have to continuously re-adjust my volume levels for the new Tabs every single time I open a new one.

This was never a problem for me prior to updating to the new Firefox 57. Please find and fix this issue. I've always liked Firefox, but this is a real pain in the ass (and ears).

It seems that this issue still occurs in 57.0.2 (64 bit) build on Windows 10. It's annoying because after pressing on every source of sound (Youtube/Spotify/Flash/etc.) sound level is not properly increased. What's more there's more than one instance of FF in Windows Volume Mixer.