I've tried plenty in the free zone and the best without a doubt for the many soft & hard clips i was after
Flash Video Downloader - YouTube HD Download [4K]
https://addons.mozilla.org/nn-no/fir...artur-dubovoy/
Did it work on every site - no
Sites like dailymotion , hulu etc were always bastards to get free to work on
Then i tried to find them on h a m s t er (one of the few that has a lot of softcore )
or nudevista if VEf fail