This add-on will direct the user to a downloader website to download the video or mp3 of your choice from youtube. Because converting video to mp3 requires a large FFMPEG server, the downloader website has safe and inoffensive advertisements, these ads are for paying the converter server rental. If you are annoyed with advertisements, then this addon is not suitable for you, look for other addons in mozilla addons that do not have ads. Thank you for understanding.