Youtube-dl is still the best downloader there is.
youtube-dl is a command-line program to download videos from YouTube.com and a few more sites. It requires the Python interpreter, version 2.6, 2.7, or 3.2+, and it is not platform specific. It should work on your Unix box, on Windows or on macOS. It is released to the public domain, which means you can modify it, redistribute it or use it however you like.
And it happens to also work with
these sites.
You just copy the url, give it you youtube-dl in a console and it will do its best to get the best quality audio and video. IF you want a specific video or audio format (or only either) you then add some command line options in front of the url.
Why can't everyone appreciate the beauty of the command line interface? It frees time to developers to do the things that matter, such as making sure the thing still works everytime youtube changes something.
Did you know that Google rudely removed all youtube downloaders from Chrome's add ons? They used to exist, but not anymore...
Most downloaders out there are really really bad. And i don't think you should be willingly be giving your viewing habits to third parties (its bad enough that Google has them). This is the real thing, and its free and open source, no ads, no tricks, no third party servers.
Did you know this beauty can download whole playlists and channels? Oh but there is more, so much more...