OK.ru Downloader is a powerful Odnoklassniki downloader that allows users to download MP3 or MP4 files with just one click. It supports downloading from Instagram and extracts music using IDL Helper, an online video to MP3 converter. The extension also allows users to take screenshots from online videos. Odnoklassniki features include downloading video in MP4 format with sound, high frame rates, and resolutions. Other features include readable file names, button styles, embedded video loading support, a screenshot button, a help section, and useful settings. However, for larger streams, the extension merges audio and video files on-the-fly in the browser.