--- 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.

update 1.1.3 coming at 12/9 and its working fine again!

Now: Unable to retrive data....Doesn t work :(

Did not work. Video metadata error. Searched for Kaner extension, which worked.

It is useless, you have three options:
1)download 320p video AND audio;
2)download video BUT NO SOUND
3)download audio but with ads AND JUST SOMETIMES!

Stupid.

Ya no sirve

The problem has been fixed by developer!
Thanks a lot!!!

-old post (8th,Dec.)-
Unfortunately, I can't download anymore.
Last night, I could download videos by my solution I wrote before. However, today I can't download.
I tried older versions of Firefox or add-on. However I can't download.
So developer, please fix it. It is my wish.

-old post (3rd, Dec.)-
Please take responsibility for your actions.
After I upgraded the firefox to ver.83.0, and I could not download videos. So as temporary measures, I downgraded the firefox to ver.82.0.3, and re-installed the add-on ver 1.1.2.
Now I can download the videos (mp4 and webm).
If you can not download videos, I recommend this solution as temporary measures, until developer will fix this problem.

This add-on is quite good, despite the recent issue I've had with it. That recent issue being that I was unable to download videos until using a VPN to hop to a different IP address. Then, the add-on worked just like it used to in the past. No idea what's going on right now, but hopefully developer gets this issue sorted out in the near future.

unable to receive video metadata from today

unable to receive video metadata
even old version and current version

thanks！

Doesnt Work. But I found one that Does :) Kaner YouTube Downloader >> Look for it GUYS it freaking WORKS :) . And I never write reviews but after one hour Searching I found the only One that REALLY DOWNLOADS!!