There are various method to do this but in this method I am going to teach you only two of them.....
Method 1: This is a simple method just the thing you have to do is replace the "www."from the
youtube video whith "ss" For an example if the link of the video is
www.youtube.com/watch?v=cpzkariGFZs
Then the modefied link should be
ssyoutube.com/watch?v=cpzkariGFZs
Personally this method if not suitable for slow connection because the download is too slow
Method 2: This Method is also identical to the previous one just the other thing you have to do is you
have to replace "www." with "XD"
In the above methods i will recommend method 2. I will not recommend to use this method unless and untill it is emergency cause the download is too slow....IDM is a better option but this can cause blue screen problem in your screen because it unnessarily accelearated the hardware capacity more than its potential...