Dota 2 is a free-to-play multiplayer online battle arena (MOBA) video game developed and published by Valve Corporation. The game is the stand-alone sequel to Defense of the Ancients (DotA), which was a community-created mod for Blizzard Entertainment's Warcraft III: Reign of Chaos and its expansion pack, The Frozen Throne. Dota 2 is played in matches between two teams that consist of five players, with both teams occupying their own separate base on the map. Each of the ten players independently control a powerful character, known as a "hero", that each feature unique abilities and different styles of play. During a match, a player and their team collects experience points and items for their heroes in order to fight through the opposing team's defenses. A team wins by being the first to destroy a large structure located in the opposing team's base, called the "Ancient".
Development of Dota 2 began in 2009 when IceFrog, the pseudonymous lead designer of the original Defense of the Ancients mod, was hired by Valve to create a modern sequel. Dota 2 was officially released on Steam in July 2013 for Microsoft Windows, OS X, and Linux-based personal computers, following a Windows-only open beta phase that began two years prior. Despite some criticism going towards its steep learning curve and complexity, the game was praised for its rewarding gameplay, production quality, and faithfulness to its predecessor. The game initially used the original Source game engine until it was ported over to Source 2 in 2015, making it the first game to use it. Since its release, Dota 2 has been the most played game on Steam, with peaks of over a million concurrent players. The popularity of the game has led to official merchandise being produced for it, including apparel, accessories, and toys, as well as promotional tie-ins to other games and media. The game also allows for the community to create custom game modes, maps, and cosmetics for the heroes, which are then uploaded to the Steam Workshop.
Dota 2 has a widespread and active competitive scene, with teams from across the world playing professionally in various dedicated leagues and tournaments. Premium Dota 2 tournaments often have prize pools totaling millions of US dollars, the highest of any eSport. The largest of them is known as The International, which is produced by Valve and held annually at the KeyArena in Seattle. Valve also sponsors smaller, but more frequently held tournaments known as the Majors, which lead up to the International every year. For larger tournaments, media coverage is done by a selection of on-site staff who provide commentary and analysis for the ongoing matches, similar to traditional sporting events. Broadcasts of professional Dota 2 matches are streamed live over the internet, and sometimes simulcast on television networks, with peak viewership numbers in the millions.