If you want to download youtube playlist videos simply follow these steps: 1. Open Mozila firefox web Browser, then click this link https://addons.mozilla.org/en-US/firefox/addon/video-downloadhelper/ and download the Addon called "Download Helper" 2. Go to any youtube playlist as you want to download all videos in that playlist 3. After select all the video links from that youtube playlist then Right click ( make sure that you've selected all videos in that playlist ) on the mouse then you can click the option "Download videos from youtube link(s)", that's it. See the below youtube video for multiple videos download from download helper addon.