Dota 2 is a 2013 multiplayer online battle arena video game and the stand-alone sequel to the Defense of the Ancients (DotA) Warcraft III: Reign of Chaos and Warcraft III: The Frozen Throne mod. Developed by Valve Corporation, Dota 2 was released as a free-to-play title for Microsoft Windows, OS X and Linux in July 2013, concluding a Windows-only public beta testing phase that began in 2011. The game is available exclusively through Valve's content-delivery platform, Steam