When I watch something on youtube and like it enough to keep, all that I do is go to my Temporary Internet files folder and copy the movie file to a safe place.
While you watch it, it downloads there. Its not like TV, it needs to download in order for you to watch it only that Youtube stores it in a temporary folder.
When on you tube or similar you see something saying 'buffering' it actually means 'downloading to temporary folder for view' and begins when it has downloaded enough for you to watch without interruptions (at least that's the intention).
You cant view anything on an Internet browser without downloading it first in one form or another.
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Ferrari 312t