Sources: https://9to5google.com/2019/11/06/youtube-terms-of-service/
https://www.engadget.com/2019/11/07/youtube-new-terms-of-service/
https://www.youtube.com/t/terms?preview=20191210#main
From Engadget:
Some parts of the updated terms:
The part in bold more clearly states that distributing content from YouTube is not allowed unless you give full credit to the author, have YouTube’s permissions to do so, or the author’s permission to do so.
In other words: No Downloading Videos. (Without credit to the author)
So sites such as Yout, VidPaw, and other services that allow free downloading of YouTube videos, along with browser extensions that allow you to do so will probably be taken down or they will notify users to give credits to the YouTube videos.
So, whoever needs to download YouTube videos, do it before December 10 when the terms update.