While Video DownloadHelper isn't perfect, it is an incredibly helpful tool while performing online research. It works quickly and efficiently, although the latest version has troubles with Twitch content (as in, it cannot capture it at all), it sometimes has issues with youtube, and doesn't always upload downloadable content while cycling through websites.

Still, if you are in the midst of a research heavy project and need to be sure that your sources don't vanish without a trace? This is the tool for you.