This add-on actually can *not* save videos. In order to save a video, it asks for downloading a 'companion' app, which is an executable that has to be installed separately and hence the browser security restrictions do not apply to it - it can do virtually anything.
This is highly suspicious, because external applications are not necessary in order to save files. I removed it and installed a different video downloader add-on which can save files just fine without 'companion' executables.
Another suspicious thing is that this addon requires some permissions which are not needed for the functionality it provides.

I want an addon that does exactly one thing, download videos. This addon used to do this, but now they have started to run videos through some kind of converter (= slow) and leaving a big watermark on the video, asking for money to remove it. Completely useless, uninstalled.

Works really well in theory, but as others have said before, it puts a huge watermark on the downloaded video, then asks you to buy a "premium" version without that anti-feature.
The add-on does not tell you that beforehand, not even in the description! Downloading a video can take a long time so it is deliberately wasting your time just to increase the chances of you paying for it. I call this misleading and a shady business practice.

It is easy to know it and is easy to use it

easy as heck to use

One of the best Add-ons for firefox. So easy to use and helpful. Thank you!!!!

Funktioniert tadellos.

on ne peut pas s'en passer,en tout cas pas moi))et un petit don de temps en temps c'est cool pour eux,et pour nous pareil pour continuer à download

Very handy, works for almost all of the media types.

100分好用免費下載工具，這輩子再也回不去了

Benutze ich seit 3 Jahren mit großem Gewinn. Mit Firefox ohne DownloadHelper zu arbeiten ist für mich kaum vorstellbar

Why does it need all these autorisations: Access to your data for ALL websites, exchange messages with OTHER programs than Firefox, consult and modify the history of downloads, access Firefox activity while browsing Internet.

It an awesome tool user friendly

I'm happy with this app. and recommend to other firefox users too.

It's really a great add-on to download videos from different web sources, which don't permit to download the video directly.

this app asks for way too many access permissions. Check carefully before accepting them.

also places a huge, intrusive QR code "watermark" on top of the content