For a long time now I have been using the YouTube Downloader browser extension, which allows you to download video or audio from the YouTube service. It is convenient because it does not require installation in the system. Also, if you decide to use a computer other than your own, just open your favorite browser (FireFox) and log into your account, after a three-second synchronization you can save the necessary video to computer's hard drive. Easy and fast, super! Thanks to the author!