[Audio Issue] Firefox Causes Background App Volume Drop on Tab Focus — All Volumes at 100%, Issue Not Present in Portable Issue Summary: Whenever I focus a Firefox tab (even a blank or safe mode one), the audio volume of background applications (e.g., Spotify) drops or changes audibly. It’s not a ducking effect (as all ducking settings are disabled), and Windows volume mixer shows all apps still at 100%. The issue happens only while Firefox is focused — not minimized, not unfocused. Reproduction Steps: Play music using Spotify or another app. Focus any Firefox window or tab. Background audio becomes quieter or altered — then returns to normal once Firefox is unfocused. Specifically on focus it will change system volume to 58, then return to what it was previously when unfocused. System Info: OS: Windows 11 (fully updated) Firefox Version: 128.0.2 (issue present since at least 127) Audio Output: Realtek and NVIDIA High Definition Audio (same issue on both) Spotify Version: Latest Windows Store version Windows Sound Settings: Communications tab: "Do nothing" All app volumes: 100% No enhancements or spatial effects enabled Troubleshooting Already Tried (No Success): Step Result ✅ Disabled audio ducking in Windows No effect ✅ Disabled audio enhancements No effect ✅ Ran Firefox in Troubleshoot Mode (Safe Mode) Issue persists ✅ Changed Firefox audio backend to winmm via about:config No improvement ✅ Fully reset Firefox profile (about:support → Refresh) Issue persists ✅ Verified with Process Explorer (audiodg.exe shows activity on tab focus) Confirms session change ✅ Ensured all apps in volume mixer show 100% No volume mismatch ✅ Rebooted and tested cleanly Still occurs ✅ Tested Firefox Portable (fresh instance) Issue does NOT occur (portable version behaves as expected) Additional Notes: The issue appears to be triggered by the main installed version of Firefox only. A completely clean portable version does not cause the volume change, suggesting something related to the system-wide install, global config, or registry entries is affecting it. Even without extensions, without playing any video/audio in Firefox, just focusing the window causes this volume behavior. What I Plan to Try Next: Fully uninstall Firefox (including deleting AppData and registry leftovers), then reinstall cleanly to see if that resolves it. Possibly test Firefox ESR if needed. Request for Help: Has anyone experienced Firefox causing audio session or DSP changes on focus, especially with audiodg.exe activity? Could there be a hidden system-level or registry config that ties Firefox to a shared exclusive audio session? Any way to trace which audio sessions Firefox creates and how Windows handles them? Let me know if you'd like logs, about:support data, Process Explorer thread captures, or a video of the issue. I’d appreciate any help from the community in narrowing this down. Thanks! —Justin