There are multiple services out there that instantly let you download the .flv (the actual video file YouTube and similar flash-based solutions use) when you enter a YouTube URL. DuckDuckGo could create a system like that as well. This file could then be forwarded to the user from a DuckDuckGo server.

In this case, the system would work on-demand, and thus not have such a big space usage, as video files will be removed from the server, X minutes after a request.
posted by Qqwy 4 years and 6 months ago Link