GitHub offers both plans for private and free repositories on the same account which are commonly used to host open-source software projects. As of April 2017, GitHub reports having almost 20 million users and 57 million repositories, making it the largest host of source code in the world.

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GitHub has a mascot called Octocat, a cat with five tentacles and a human-like face.

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Development of the GitHub platform began on 1 October 2007. The site was launched in April 2008 by Tom Preston-Werner, Chris Wanstrath, and PJ Hyett after it had been made available for a few months prior as a beta release.

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Projects on GitHub can be accessed and manipulated using the standard Git command-line interface and all of the standard Git commands work with it. GitHub also allows registered and non-registered users to browse public repositories on the site. Multiple desktop clients and Git plugins have also been created by GitHub and other third parties that integrate with the platform.

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The site provides social networking-like functions such as feeds, followers, wikis (using wiki software called Gollum) and a social network graph to display how developers work on their versions ("forks") of a repository and what fork (and branch within that fork) is newest.

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A user must create an account in order to contribute content to the site, but public repositories can be browsed and downloaded by anyone. With a registered user account, users are able to discuss, manage, create repositories, submit contributions to others' repositories, and review changes to code.

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The software that runs GitHub was written using Ruby on Rails and Erlang by GitHub, Inc. developers Chris Wanstrath, PJ Hyett, and Tom Preston-Werner.