Youtube-DL works great. Download from https://youtube-dl.org/. To use, type youtube-dl <url> code example

Example 1: downloading youtube playlists using youtube-dl in highest quality

youtube-dl -f 22 'http://www.youtube.com/watch?v=P9pzm5b6FFY'

Example 2: downloading youtube playlists using youtube-dl in highest quality

youtube-dl -f best 'http://www.youtube.com/watch?v=P9pzm5b6FFY'