Sound Adjuster, developed by tropic, is a Firefox extension that adds in-browser audio controls for site-specific listening needs. The extension places sliders and controls in the browser to manage individual tab volume, stereo balance, amplification and frequency equalization without leaving web pages. It includes per-tab management, a slider-based interface, and a five-band equalizer for direct playback adjustments. Aimed at Firefox users who encounter low-volume media or prefer tailored equalization for music and videos.

It applies real-time audio processing inside each tab

The extension runs processing inside the browser using the Web Audio API to modify playback as pages play. Manifest V3 compatibility is included to match modern extension security and performance expectations. The project is open-source and hosted on GitHub, and the developer documents a privacy-first approach, explicitly stating there is no data collection or external tracking by the extension.

Controls expose numerical ranges and named frequency bands for fine adjustments

Control granularity is measurable

It keeps a small footprint and runs across desktop and mobile Firefox

The extension targets Firefox on desktop and Android, so it operates within the browser process and not at the system mixer. The developer describes a lightweight design with minimal resource impact, and the extension supports multi-frame environments and embedded iframes. Because it runs inside Firefox, it remains scoped to browser audio, and compatibility depends on standard HTML5 audio/video implementations rather than system drivers.

The extension suits users who need browser-scoped audio control, with one clear limitation

The extension is a practical option for Firefox users who require precise, site-specific audio adjustments and prefer an open-source, privacy-conscious tool. Its browser-scoped design means it does not replace system-wide mixers or global audio profiles, so users seeking OS-level mixing should look elsewhere. In practice, the extension fits anyone who needs in-browser audio tweaks rather than system-level control.