how to download vedios from you tube directly on the site

hii guys in current time there r many applications that allow us to download you yube vedios.........
bt acc. to me(LUCKY SHOBHNANI)  there is no need of such apps.....

for example
let take a vedio url

https://www.youtube.com/watch?v=g9JSAOF8ueM

now if we replace http://www.  by ss
eg 

ssyoutube.com/watch?v=g9JSAOF8ueM

then after entering above url u will go on a new page of save.net web site from that u can download it in any format

thnks.....for more info contact me @ shobhnanilucky@gmail.com

ls creations.........jst be L.S.