If you're using Windows 10, you can click on the volume control on the right of the task bar, as shown below. It's easy, although it doesn't allow you to control tabs individually.
I wanna suggest a feature for the desktop firefox, altough given my experience so far, it's more than likely that this new suggestion, just like the previous one, will fall on deaf ears, so to speak and nothing will change. My previous suggestion about adding "about:config" to the mobile Firefox received a lot of votes, months passed, if not even a year and still nothing was done about it and the mobile browser still doesn't have "about:config". That's why I have my doubts that this new suggestion of mine will ever see the daylight but I'll post it anyway.
When using a live chat on a website (usually for remote tech support of a product), that live chat produces a sound whenever the tech support operator sends you a new message. However, that sound is always so loud that it could wake up the dead. I don't wanna change the sound volume for my entire browser, so I suggest an option to be added in the contextual menu of every tab - "Sound volume for this tab" which would bring up a menu/dialog window with a slider where the user will be able to manually change the sound volume for the given tab. And ofc that setting will have to be permanently stored in the user's profile (not in the browser cache).
Honestly this feature would be great. I switched from Chrome to Firefox a while back and this is the only feature that's making me want to switch back to Chrome. There's a working extension that gives per-tab volume control on Chrome, but it doesn't work on Firefox and there are no alternatives (I'm guessing due to how FF is configured, the extension cannot be created in the same way). I'm like 99% sure that Mozilla does not care about this feature enough to ever do anything about it (or else they would have already), but why not loosen the necessary restrictions to allow a 3rd party to create a functional extension for this purpose?
Agreed. This is needed. Watching one low-q video on a tab, while multi-tasking. I wish I could just boost the one tab and properly balance my audio, while multitasking.