Funciona perfeitamente.

Excellent, very easy. And works beautifully!

STILL cannot do video PLUS sound..
will not do ytube 'raw' eg spherical for 360

ÇOĞU ZAMAN GÖREVİNİ YAPMIYOR

Do not work: "Batch downloading is interrupted."

Excellent accessories! Thank you for its development.

A bit frustrating installation of stream merge software. Rare cases of misleading information about some streams (only video that really contains video+audio).

Works! I have a mac and use firefox, and at the time of writing this, the extension does what says it'll do. The icon appeared, I asked it to download a video off youtube, it did, job done.

Extremely complicated installation. I followed the first step in the "About this extension" section, install "native client" (whatever that is) - nothing. I don't really need or want HD - my connection has a data limit - but I decided to try installing the ffmpeg thing too. It hasn't helped. The icon below the video produces a big orange box with only an hourglass in it. "Quick download" (upper right corner of the browser screen) produces a "Please Wait" message but the browser shows no download in progress and if there is one, I have no idea where it's been saved (I looked in all the usual places). The Settings page includes something about an "ffmpeg path" with a box that's empty; maybe it's supposed to have something in it but I don't know what. I don't understand most of what's on that Settings page anyway. This extension may be fine for people with a lot of knowledge of how addons work but that doesn't include me and I'm stumped. From my point of view, basically - it doesn't download anything and I don't know what to do to make it start. I'm removing it.

By default, is not working for audio-only, downloaded files not working ... need more steps !

1) The download popup window is SPARSE as hell, please remove all the white space.
2) Use standard Firefox file download feature - i.e. ask the user where to download the file please.

Otherwise it's currently the only add-on which works. Thank you.

All I can say is WOW!!! An HD YouTube downloader that actually downloads the video as HD!!!

--- December 9, 2020 ---
I've been waiting for this moment, albeit only for a few days!
Updated to 1.1.3 and has made a dramatic comeback!
I look forward to working with you!

--- December 3, 2020 (2) ---
Even Firefox DEVELOPER has stopped working completely.
However, when I tried the method of lowering the version of Firefox suggested by others, it certainly works.
In addition, we have confirmed that older versions of add-ons (0.8.9 to 0.9.4) also work.
I would like to wait for a while as it is.

--- December 3, 2020 ---
In my environment, I confirmed that it works normally by changing the Firefox Browser to the DEVELOPER version.
If you are already using the DEVELOPER version, please remove the add-on and re-install it.
In normal Firefox, all versions (0.8.1-1.1.2) do not work.

--- December 2, 2020 ---
It's a nightmare again.
In addition, even if you use the old version (0.8.9-0.9.4) this time, you cannot download it at all.
After all, has the cat-and-mouse game started between YouTube management and add-on makers?

--- November 7, 2020 ---
Although it has already been reported, it seems that some AVC format videos have a capacity of 0B and cannot be downloaded.
Not all AVC formats, only a few at this time.
The cause may be that the URL of the video file is different from the others.
This video file cannot be downloaded even with versions 0.8.9 to 0.9.4, so you need to wait for support.
Also, there are no particular problems with VP9 or AV1 format videos.

--- November 6, 2020 ---
Yesterday, it was updated to 1.1.2, and a great add-on is back!
However, it doesn't seem to work with older versions of Firefox.
It's a great pleasure for the time being, but we'll have to continue to be frightened by the quiet changes in YouTube's specs in the future ...

----------Old post 1----------
↓ Install Ver.0.8.9 to 0.9.4
https://addons.mozilla.org/ja/firefox/addon/youtube_downloader_webx/versions/

I posted it 3 days ago, but I've found a solution, albeit incomplete, so I'll post a new one.
We have confirmed normal operation with Ver.0.8.9 to 0.9.4.
When downloading AV1 8K video, select "MP4 high resp" as the format.
In the case of WebM format, all resolutions of 4K and above are displayed only as "WEBM 2160p".
It is necessary to judge the resolution from the data size.
Also, it seems that you can download HDR videos, but it is a little difficult to understand because there is no notation.

----------Old post 2----------
Of the many YouTube download add-ons, it's especially nifty.
Although it is free, it also supports 8K, making it extremely versatile and easy to use.
However, just a few hours ago, "pathname is undefined" or "No Link Available for This Video" was displayed and it stopped working.
An early solution is awaited.

↑↑↑ I translated it with Google Translate, so I'm sorry if there is something wrong with it.