Sound Adjuster
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Listening guides

A few steps to better listening.

Sound Adjuster is a free, open-source volume booster and 5-band equalizer for Firefox. Use these guides with the extension, or try its controls in the website demo.

By tropic · Updated 3 September 2026 · Based on Sound Adjuster 2.4.1

Control names below match the English extension interface. Demo settings affect the sample only and are not copied to the extension.

How do I boost quiet audio in Firefox?

Use Gain to increase the level of supported audio and video in the current tab. Sound Adjuster offers a range from 0x to 5x; 1x is the original level.

  1. Install Sound Adjuster from Firefox Add-ons, then open a page with audio or video and start playback.
  2. Check the player volume, tab mute state and device volume first. Open Sound Adjuster from the Firefox toolbar.
  3. Increase Gain gradually from 1x while listening. If the sound crackles or distorts, reduce it. A higher gain does not repair a poor recording.
  4. Close the popup when the level feels right. Processing stays active in that tab. Return Gain to 1x to remove the volume boost.

To change the tone, open Equalizer and adjust its five bands or choose a preset. Gain changes the overall level; the equalizer changes the balance between frequency ranges.

Try the interactive demo

How do I remember sound settings for a website?

Turn on Remember to restore your chosen gain, balance, channel and equalizer settings when you return to that site. You can also keep several named profiles for the same site.

  1. On the website you want to configure, open Sound Adjuster and set the sound as you like it.
  2. Enable Remember in the footer. Reload the page to check that your settings return.
  3. For another setup, open the footer menu, choose Profiles, then Save current… and give it a name. Select a saved profile to switch setups.
  4. Turn Remember off to stop restoring the current settings automatically. This leaves the sound in the current tab unchanged. Use Manage profiles to remove named profiles.

Settings stay on this device and are not synced. Site profiles are not saved or read in private windows or on non-HTTP(S) pages. Remember restores your choices; it does not automatically equalize the loudness of different videos.

Try the interactive demo

How do I adjust left and right audio balance?

Use Pan to move supported tab audio toward the left or right. The center value, 0, keeps the balance centered.

  1. Play a stereo recording at a comfortable level and open Sound Adjuster. Headphones make the difference easier to hear.
  2. Move Pan left or right in small steps. Return it to 0 whenever you want centered balance.
  3. Enable Mono to combine the stereo channels, or Flip L/R to swap them. These controls do different jobs from Pan.
  4. If you want the same balance next time, enable Remember for the site. These controls affect browser media, not the sound of other apps.
Try the interactive demo

Why might the controls be unavailable?

Sound Adjuster works with standard HTML audio and video. Protected playback, cross-origin media and browser security restrictions can prevent processing. Read the availability message in the popup. On unsupported media, the extension leaves playback unchanged.

Installation and support

Install from Firefox Add-ons

Source code and release notes