how to download youtube or any kind of video using firefox

We will need an addons.   
download it from here.
click allow if asked.
then restart firefox.

now you will see something like this

go to youtube.com and play any video. if you are using idm download will start automatically. if you don't have idm, follow this 3 steps:


1) click here:

2) click any one, but i prefer SD.

3) download will starts n keep enjoying
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