Butter — Tab Volume Booster by Polaco Dev

Butter boosts the volume of individual Firefox tabs up to 600% and shapes their sound with a 10-band equalizer. Quiet video? Turn up just that tab, without touching the others.

Volume per tab
- Boost from 0% to 600% with a gauge, slider, quick presets (50–600%) or the mouse wheel
- Built-in limiter, so heavy boosts get louder instead of distorting
- The toolbar icon shows each tab's boost

Equalizer
- 10 bands (32 Hz to 16 kHz, ±12 dB) with a live frequency-response curve
- 10 presets: Flat, Bass boost, Bass reducer, Vocal, Treble boost, Rock, Pop, Electronic, Jazz, Classical
- Global mode: saved and applied to every tab
- Per-tab mode: give a single tab its own EQ, overriding the global one

Manage every tab with audio
See which tabs are playing, boosted or muted, control any of them from the same popup, or jump straight to it.

Also
- English, Portuguese and Spanish (follows Firefox or pick one)
- Light, dark and automatic themes
- No data collection, no tracking, no remote code

Limitations
DRM-protected media (Netflix, Spotify, etc.) and cross-origin media served without CORS can't be processed. Firefox would mute them, so Butter leaves them at normal volume. Firefox doesn't allow extensions on about: pages or addons.mozilla.org.

Open source (MIT): https://github.com/joaoregis/butter-tab-volume-booster