4K Download Online is described as 'Download YouTube music from your browser and save it in MP3, M4A or OGG with the best possible quality' and is a YouTube Downloader in the Audio & Music category. There are more than 100 alternatives to 4K Download Online, not only websites but also apps for a variety of platforms, including Windows, Mac, Linux and Android. The best alternative is youtube-dl, which is both free and Open Source. Other great sites and apps similar to 4K Download Online are Youtube-DLG (Free, Open Source), 4k Video Downloader (Freemium), Video DownloadHelper (Freemium) and ClipGrab (Free, Open Source).
VDYoutube is a free web service that allows you to download videos and audio files from sites like YouTube, Facebook, Twitch.Tv, Vimeo, Dailymotion and many more. All you need is the URL of the page that has the video you want to download.
YDL-UI provides a simplified way to download videos using youtube-dl , without the hassle of using the command-line. This is achieved by dynamically generating youtube-dl argument queries that can be run with a click of a button.