Dirpy, download Youtube audio & video without Firefox extensions

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A few times I've been asked "how do I download a Youtube video" or the more complicated "how do I download the audio from a Youtube video?" Now both answers can be solved with one web site: dirpy.com. Dirpy is a Google-backed site that lets you download audio from Youtube videos in .mp3 format. It also offers up videos in a variety of resolutions. No more Firefox add-ons and then stripping out audio, dirpy makes getting Youtube content simple.