5K Player also features DLNA server playback so videos you grab can be watched on any devices on your home supporting DLNA network; it supports AirPlay for quick playback to supported devices. Pick a video in the library and you can do a quick conversion to MP4, MP3, or even ACC (an audio format preferred by iOS devices). The player didn't like playing back the overly large 4K file though and experienced buffering issues—VLC didn't have any problem with the same file. Ultimately, there's a lot to like about 5K Player, from the price to the features, especially if you look at them as extras on a downloader. But the interface and playback issues may have you looking elsewhere.
If you are looking for a free online video downloader which supports downloading any video online from any site using URL, you definitely can not miss VidPaw Online Video Downloader. VidPaw is able to convert videos from YouTube, Vimeo, Instagram, Facebook and so on to many formats like MP4 in high quality. No software is needed and easy to use on both Windows and Mac.
If you're willing to do more about the offline YouTube videos, you can try the its advanced version - MacX Video Converter Pro. Comparing with MacX YouTube Downloader, It not only allows you to download YouTube SD/HD/4K videos on Mac, but also convert them to all general-purpose formats, and common devices profiles, edit the downloaded YouTube videos, record screen videos from both desktop and iPhone, or capture videos with webcam. Besides, if you have DVD sources, you can also take advantages of this program to rip DVD to any formats and devices, or make a backup of your DVD movies without any quality loss.