GainDial by Fenix

I built GainDial for myself because I wanted a straightforward way to control the volume of individual tabs. It ended up being useful enough that I decided to share it.
You can mute, lower, or boost audio from 0% to 500%, with a separate setting for each open tab. If a player doesn’t respond normally, Compatibility mode may help.
GainDial works entirely in your browser. There are no accounts, ads, analytics, tracking, data collection, or network requests.
DRM-protected sites and some unusual players may not work. Boosting audio past 100% can also cause distortion depending on the source, so turn it up gradually.