You can do it with a browser add-on or an independent dedicated App on your computer. I don't know if I can recommend what you can use on here though.
I could have sworn the use of "Google it" was frowned upon here.
I read that if you install, .ss., between "YouTube", and the specific video link, it makes it downloadable.I know they have a monthly service for this feature but I was wondering if there is a free, legal way to do it.