This document discusses the history and development of social networking sites (SNS). It begins with defining SNS as internet-based platforms that allow users to create profiles and connect with other users. The document then outlines some of the earliest precursors to modern SNS, such as Usenet systems, Bulletin Board Systems, and early online services like CompuServe and AOL. It traces the evolution of instant messaging and early social networks like forums, SixDegrees, and LiveJournal. The document highlights major advances including Friendster, Myspace, LinkedIn, and Facebook. It also covers media sharing sites like Flickr and YouTube, as well as real-time updates on Twitter and Tumblr. The document concludes with details on