Best one I've found so far. Good job

es uno de los pocos que descarga MP4 con Firefox, amo esa extension.

it works great and all, but the mp4/video part stopped working it says its been disabled when i try downloading a video. UPDATE: hey when are you gonna fix this button disappeared again i love this addon but keeps disappearing and downloading is an issue and its been about well almost a week 1/2 to be exact if you can pls keep this from happening again pls and what if nobody has money to upgrade or donate to you

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it works now! before it didnt but now it does! im rating it four and not five because you have to pay for a lot of features and it doesnt always work, but its the best extension i have tried!

This extension actually works, however, It is almost impossible to locate the real downloading URL location/button because the author has liberally added adverts which look as though they would be the download URL for this (good) firefox add-on. For instance, I just received an email touting an improvement to this add-on, but was unable to locate the download url to it.
UPDATE: improvements no longer have to be downloaded, since they automatically are installed by this extension.
If you can find the URL for the Author's support email, you will actually get a response in about 3 days. My experience is that if you don't give up after receiving the first, generalized response, you will eventually be very satisfied by the author's support, e.g., it took me 4-5 emails to get exactly the information I was seeking.

Works well, except that one needs the paid version of it in order to download at decent quality.

Good extension.Thanks.

I have the free version and most of the time it works great. Sometimes it doesn't work for one reason of another, but it normally gets fixed within a week. I wonder if the pro version has the same problems? If it doesn't, I would probably pay for it. Regardless I would recommend this add-on, just try to be patient when YouTube changes its coding and the add-on needs to be updated.

Its quite but refuse to donwload sometimes

16.13 not work.the button is invisible

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best option i have so far for downloading youtube vidoes