I've had minor problems with the co-app and didn't use for awhile. but its remained one of the best extension of its kind, and works when many others have failed. go through the settings and pay attention and it will work for you.
EDIT: Sometimes you need to start the video first, other times you CAN'T. and other times you have to start it and select a resolution quality. mostly it's the first.

It doesn't work anymore. At all. I paid for the full version, and it hasn't worked for months.

Je l'utilise depuis plus de 10 ans, il enregistre à peu près tout, évolue avec les différents formats, l'appli est maniable, le suivi du téléchargement est visible avec les infos de la video en cours.
à mon avis c'est le meilleur enregistreur, de videos sans pub,
je suis très satisfait et je recommande vraiment!!

とても使いやすくてライセンスも購入して愛用していますが、
またYouTubeの仕様変更により、機能しなくなりました。
いつも１週間くらいで修正して使えるようにしてくれるのに、今回は１か月以上放置している状態。
もうアップデートは諦めたのでしょうか？
Vimeoやニコ動などではまだ使えるので、
またYouTube側の対策に対応できていないようです。
早くYouTubeの仕様変更に対応してください。

Tenho limite de download? Qual?

Download Helper has helped me save 100s of file that would have been a challenge to obtain otherwise. I am very happy with the product.

indispensable et si il pouvait capturer également les sous titres se serait exceptionnelle.
Bravo

This application is a very good way to download many videos. Unfortunately not working with some videos and the devs required some payment. It's useful overall.

Es fantástico, intuitivo, eficaz y muy fácil de usar. Me ha encantado

The new version in beta 9.3.7.0 fixes the recent media non-detection bugs. It's impeccable, and I've rediscovered a very useful Mozilla extension. Thanks for the development! - La nouvelle version en beta 9.3.7.0 corrige les bugs récents de non détection de média. C'est impeccable, je retrouve une extension bien utile dans Mozilla. Merci pour le développement !

This application is a very good way to download many vids.