This article applies to Windows only.
If your Windows volume mixer has a slider for each open Firefox tab, this is a bug related to multiprocess (E10s) that will be fixed in Firefox version 76.
In the meantime, in Firefox versions previous to 76, you can set the number of Firefox processes to "1" to resolve the issue:
Setting the number of processes to 1 effectively turns off the multiprocess feature, which may significantly affect Firefox's performance.
- In the Menu bar at the top of the screen, click and then select or , depending on your macOS version.Click the menu button
and select .
- In the General panel, scroll down to Performance.
- Remove the check mark next to Use recommended performance settings.
- Choose 1 in the drop-down menu for Content process limit.
