There have been many ups and downs when it comes to pulling the videos that you want back off the web and with youtube constantly updating their streaming protocols certain browser extensions such as BYTubeD no longer work. It is for that reason that I am going to list the ones that still work.
1. 4K video downloader Mac / PC (free/$9.95), my new favorite and totally worth $9.95 to get unrestricted features for bulk downloading. in the preferences menu you are able to control the number of simeltanous downloads to avoid getting your ip address blocked by youtube. So how else are you gonna download 200 twerking videos off youtube?
2. Clipgrab Mac / PC / Linux (free), Clipgrab is constantly being updated and is absolutely free. Only con is that it can only download one video at a time.
3. CYS Audio/Video Downloader Firefox extension (free); This is one of the few remaining browser downloading scripts that actually works. It is also constantly being updated, but usually requires the “experimental versions” to get things working again.
-Hope these help you to get your visuals under control.