How does YouTube prevent video content from being saved/redistributed?

Question

Sure, you can embed a YouTube video on any site, but the content ultimately must come from their server. What technology(ies) do they have that prevents us from saving/redistributing content?

From a protocol standpoint, you would think that anything that comes over the wire could be saved. I hope I am not the only guy on Earth who does not know how to "save" a YouTube video...

Answer 1

There are a couple of plugins for Firefox out there that let you save the content. Basically it parses the sourcecode and looks for the videofile (either .flv or .mp4) and downloads that directly. The flash player on the page just plays the supplied file. They could of course obfuscate the path to the video file, but that can be reverse engineered as well. They can't really do anything about it, because the video file has to be on the user's computer at some point, or if not, the stream could be intercepted as well.

eg. https://addons.mozilla.org/de/firefox/addon/6584/?src=api

Answer 2

Mostly it's a legal deterrent rather than technical. There are a plethora of programs out there that will allow you to download their video. But there are two things they do that help reduce unauthorized downloads:

1. Use is flash to control the download and playback.
2. Hosting video yourself is not cheap, and thus it's much easier to simply leave the video on youtube.