The 4K Video Downloader quickly and easily downloads youtube video files just by pasting the url of the video. You can choose the file format and file size. I, usually, choose MP4 and just 360 frame height, preferring smaller files.
This website offers the 4K Downloader program:
https://www.4kdownload.com/-bzs8q/video-downloader?r=free_license
My downloaded files are found in a folder called 4KVideo but there is also an option to change the destination folder. I stream workout video files with motivating music downloaded from youtube to exercise without an interruption from an ad. An ad can really ruin a workout or even cause an injury. Seriously, I have almost fallen off my bungy rebounder when an ad abruptly interrupts.
Best of all, the files will stream to a TV connected to a ROKU device also without ads unlike the ROKU youtube app.
I can use the ROKU media player to stream a file directly from my laptop hard drive or my mobile phone using the Web Video Caster browser.
There is also the option to download the program directly to an android device so the video file can be downloaded directly on to the device or even an mounted sd card.