Media Converter and Muxer


After installation, a toolbar button will be placed in your Firefox toolbar. By clicking on the button, the conversion window appears. This window will let you do the following operations:
1. Convert a video or an audio file into a local MP3 file.
2. Mux audio stream out of video files.
3. Combine an audio-only file with a video-only file into a normal stream.
4. Change the volume of a video or an audio file.
5. Change screen size of a video file.

Note: This extension is not a YouTube downloader.


There is a WebExtension import of this add-on; Please give it a try and let me know if a feature is missed

Note: This extension requires FFmpeg audio and video converter to perform all its conversions. If you already have FFmpeg in your system, most likely the extension will find it and use it. If not you can point the extension to use the installed FFmpeg. If you don't have FFmpeg though, then you have two options. Either let the extension to install it for you or manually get it from and then ask the extension to use the downloaded executable.

Note: To perform conversion just drag and drop your local file(s) into the conversion window.

Note: The extension supports file conversion from online media streams. Just drag and drop the link to the conversion window. The extension will download the file and perform requested conversion.

Note: If for any reason you would like to abort the current operation, you need to force stop FFmpeg process from your OS activity monitor. Next version will implement this feature in the UI.

Note: This addon contains an easy-to-use API for other developers to perform conversion in a few lines of code. If you are a developer and would like to use these APIs check this documentation,

Note: For bulk media downloading visit

Download files:


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