Since most Youtubers often sort videos into different thematic playlists according to the property of the video and the interest of the wide Youtube users. Becuase the servers only have limited amount of space every 2 hours approximately the server will delete files that were being downloaded more than 2 hours ago. If you are downloading your Playlist and the server were to delete that file you would download an empty file. In order to prevent such events the download limit per playlist is videos. After confirming the parameters, it will start to download videos from YouTube playlist automatically. You can also input as much as URL links manually, just input the .