RSS Button for Safari is a lightweight native app extension for feed discovery in Safari. To install, you simply open RSS Button for Safari, choose your preferred news reader, enable the extension from Safari Preferences under the extensions tab, customize the toolbar, and add the RSS Button.
RSS Button for Safari requires either a desktop news reader supporting RSS, Atom or JSON feeds or an account with an online news reader such as Feedbin, Feedly, FeedHQ, Inoreader, NewsBlur, The Old Reader, Minimal Reader or BazQuz Reader.