GitHub is a web-based hosting service for software development projects that use the Git revision control system. GitHub offers both paid plans for private repositories, and free accounts for open source projects. As of May 2011, GitHub was the most popular open source code repository site. GitHub Inc. was founded in 2008 and is based in San Francisco, California. In July 2012, the company received US$100 Million in Series A funding, primarily from Andreessen Horowitz. The site provides social networking functionality such as feeds, followers and the network graph to display how developers work on their versions of a repository. GitHub also operates a pastebin-style site called Gist, wikis for individual repositories, and web pages that can be edited through a Git repository. As of January 2010, GitHub is operated under the name GitHub, Inc. The software that runs GitHub was written using Ruby on Rails and Erlang by GitHub, Inc.