Keepvid is a free online video downloader that allows users to convert and download videos from various streaming platforms, including YouTube, Facebook, and Dailymotion, into formats like MP3 and MP4. The service supports over 10,000 websites and offers high-quality downloads, with speeds increased by up to 500%. Users can easily download videos by copying and pasting the URL into the Keepvid interface, making it a user-friendly tool for accessing online video content without the need for software installation.