Great, when it wants to work. Lately it's been failing all the time!!!!

Slowed the whole operating system. Unintuitive. Slow downloads. Not good.

It does download videos from some sites, so credit for that. But the implementation of the ADP video restriction in the free version is awful. It WILL download those, but then it runs for a long time re-encoding the video to add their huge watermark. That's MUCH worse than just not downloading ADP videos or saying "please upgrade for that". And puts the burden on you to remember not to waste time and CPU downloading those, just to end up with garbage.

it used to be great, now free to install, requires additional software install, then tells you pay to use. I'm uninstalling and finding alternatives.

what happened to the ability to download via mp4? all I'm seeing is the ability to download adp/mkv, and there the download stalls... ???

Videodownload works and did well for years. But now it converts the downloaded video without being asked to and then plants a fat QR code "watermark" in the top left corner if you don't buy the extension.

Ineterfejs to jest dramat, korzystanie z tego programu to droga przez mękę.
Video jakoś ściąga, ale trwa to strasznie długo, w darmowej wersji wideo jest słabej jakości i ma wstawiony wielki kod QR.

AFTER INSTALL. NO ICON SHOWS UP IN THE BROWSER???????

Requires a companion app for Youtube and puts a huge QR code on the videos needing to be converted.

It's paid software, don't install it, if you don't want to pay.

Well.... in short: On my Ubuntu machine (Ubuntu 22.04, Firefox 107.0.1 64bit) I get mostly errors on YouTube. Interestingly one download yesterday worked fine - but it was the only one.
The downloadable files are listed, but... as mentioned: VideoDownload Helper says: Data may be corrupt - and refuses download. Only those videos are downloadable, which - anyway - can be downloaded using "download media" from Firefox directly. And this isn't the sense of the addon, because such downloads are simple to manage without addon.
Edit:
This is strange:
ffprobe version n4.1.5-vdhcoapp Copyright (c) 2007-2020 the FFmpeg developers
built with gcc 9 (Ubuntu 9.3.0-17ubuntu1~20.04)
configuration: --arch=x86_64 --prefix=/home/mig/git/vdhcoapp/converter/src-build/linux/64/converter-build --extra-version='"vdhcoapp"' --extra-cflags='"-I/home/mig/git/vdhcoapp/converter/src-build/linux/64/deps/include"' --pkg-config=pkg-config --pkgconfigdir=/home/mig/git/vdhcoapp/converter/src-build/linux/64/deps/lib/pkgconfig --extra-libs='"-ldl"' --enable-shared --enable-gpl --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxvid --enable-libx264 --enable-libaom --enable-avresample --disable-indev=sndio --disable-outdev=sndio --disable-doc --disable-ffplay --extra-ldflags='-L/home/mig/git/vdhcoapp/converter/src-build/linux/64/deps/lib -L/home/mig/git/vdhcoapp/converter/src-build/linux/64/zlib'
WARNING: library configuration mismatch

This WARNING irritates me - any idea?

Beware: Works only occasionally - but usually requires a "companion app" that Apple won't let it download because developer "has not had it checked for malicious software."