When it comes to tools for downloading YouTube videos, there are thousands of them. However, very few let you download multiple videos at the same time. BYTubeD is a Mozilla addon that lets you download youtube videos in bulk on any given page.
After you have installed the add-on, simply go to Tools and select BYTubeD on any page that contains YouTube videos. From the list of videos displayed, you can select all the videos by doing Ctrl+A or choose specific videos that you want to download. The videos will be saved in the specified folder. You can also choose to get the high-quality versions when available.

Features:
- Download YouTube videos in bulk.
- Download all or selected videos on a page.
- Use text filters to select videos.
- Choose to download high-quality versions.
- Handy for downloading YouTube playlists.
- Choose format preference of FLV or MP4.