What are some alternatives?
youtube-dl - A small command-line program to download videos from https://alternativeto.
yt2mp3.org - Free online YouTube to MP3 Converter
4k Video Downloader - 4K Video Downloader is a software program that helps people download video files from sites such as Facebook, YouTube and Dailymotion.
YoutubeDownloader - YouTube Downloader is a best in the class video downloader for the Opera web browser.
Youtube-DLG - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
Peggo.tv - Peggo is a free YouTube to mp3 converter online.