Media Device Router for Firefox

Media Device Router lets you manually choose which microphone and speaker a website uses, instead of relying on the system default. Useful when you regularly switch between audio devices — headsets, virtual cables, conferencing hardware — for calls, streaming, etc. WHAT IT DOES

• Pick a speaker/output device per site using Firefox's native device picker (selectAudioOutput) or a simple dropdown.
• Pick a microphone per site; the extension injects that device into the site's own getUserMedia() calls.
• Remembers the choice per hostname and reapplies it automatically the next time you visit.
• Reapplies the saved speaker when a site swaps audio/video sources on an existing element without a full page reload (single-page apps like YouTube).
• Settings page to review, manage, or forget saved sites, and switch between light/dark/system appearance.

HOW TO USE IT

1. Open the site you want to route audio for.
2. Click the toolbar icon, then "Open permission selector on this page."
3. Grant microphone permission if prompted, then choose your microphone and/or speaker. Your choice is saved automatically and reused on future visits to that site.

LIMITATIONS (please read) This extension works within the audio permissions Firefox and each website allow — it cannot bypass them. In particular:

• It cannot change the microphone of a capture that's already active; reload the page or restart the call after changing the selection.
• Speaker routing depends on setSinkId()/selectAudioOutput(), which some sites restrict via a Permissions-Policy header.
• It cannot reach audio inside iframes, workers, or AudioWorklets that are out of the content script's scope.
• Because of how Firefox resets audio output internally on some sites, a brief reset to the default speaker may occasionally be visible before the extension reapplies your choice. It is not guaranteed to work identically on every website.

PRIVACY No data leaves your device. All preferences (per-site device choice, theme) are stored locally using the standard browser.storage.local API — nothing is sent to any server, and the extension collects no data of any kind.

PERMISSIONS

• host_permissions (<all_urls>) and "scripting": required so the router can work on any https:// site you choose to use it on, not just a preset list.
• "storage": required to remember your per-site device choices and appearance setting locally.