![Firefox Firefox](/uploads/1/2/5/0/125031898/348871264.png)
There are a number of add-ons which you can install to download youtube videos, but I don't recognize the one you described. You'd have to ask your friend what the name of it is.
Sep 14, 2017 Downloadhelper is a Firefox addon that allows Free YouTube Videos Downloads. Video DownloadHelper Browser extension to download videos from the Web.
However, here's one that does a similar job: https://addons.mozilla.org/en-US/firefox/addon/flash-video-downloader-youtube/
![Firefox mozilla youtube downloader Firefox mozilla youtube downloader](/uploads/1/2/5/0/125031898/254581748.png)
Firefox Youtube Video Downloader
In the screenshot, you can see a blue arrow on the toolbar. If you click that, you get the option of downloading that particular video in a number or diferent formats like High Definition (HD) for example.
Mozilla Firefox Youtube Video And Audio Downloader
If the arrow remains greyed out on a video, it means that downloading has been disabled by the site.