Mono Audio Mixdown — Zapp

Mono Audio Mixdown

Stop missing half the audio. This extension forces stereo audio to mono on web pages, so videos and audio mixed to only one channel play properly in both ears. Single-channel audio is a surprisingly common production mistake, and this fixes it.

Who this is for

• People with single-sided hearing loss or deafness in one ear. If you can only hear one side, audio mixed to the other side is silent for you. This extension fixes that on any site you allow.
• Anyone listening with one earbud. Walking, working, or sharing an earbud causes the same problem and gets the same fix.
• People who find single-channel audio uncomfortable or disorienting. Mono playback in both ears feels balanced and natural.
• Anyone who hits "broken" audio. Old uploads, badly-encoded podcasts, amateur livestreams, and lecture recordings where the lavalier mic was on the wrong channel all become listenable.

How it works

For every video and audio element on a page, the extension combines the left and right channels into a single mono signal, then sends that signal to both ears. Properly mixed stereo content stays balanced. Broken single-channel content becomes audible everywhere it should be.

You can toggle the effect:

• Per site. Force on, force off, or follow the default on any individual website.
• Globally. Set a single default that applies everywhere unless you've overridden it for a specific site.
• With adjustable sum gain. Keep the default for full-volume accessibility playback, or lower it slightly if proper stereo content sounds too loud after summing.

A small status indicator in the popup tells you whether the extension is active on the current page and how many media elements it's handling.

Privacy

This extension does not collect, transmit, or share any data. Your settings are stored locally in your browser and never leave your device. There are no analytics, no telemetry, no remote servers, and no accounts.

What it can't do

A few honest limitations worth knowing before you install:

• DRM-protected playback. Services like Netflix, Spotify Web Player, and Apple Music decode audio in a protected pipeline that no browser extension can reach. The extension will have no effect on these.
• Some cross-origin media. If a site loads audio or video from a different domain without the proper CORS headers, the browser blocks extensions from processing it. Most major platforms (YouTube, Twitch, Vimeo, podcast players) work fine. A small number of sites that hotlink raw media files may not, and you can simply force the effect off for those sites.
• Browser internal pages (about:, the Add-ons site, and similar). Firefox doesn't allow extensions to run on these, by design.

After you install

Click the toolbar icon to open the popup. Set your default behavior, then visit a site and override it if needed. That's all the setup there is.

If a page was already open when you installed or enabled the extension, reload it once so the audio routing can attach.

Source code

This is a small, auditable extension. The full source is available for anyone who wants to read or build it themselves. -> https://github.com/itsZapp/Mono-Mixdown