Valve Corporation, also known as Valve Software, is an American video game developer, publisher, and digital distribution company headquartered in Bellevue, Washington. It is the developer of the software distribution platform Steam and the game franchises Half-Life, Counter-Strike, Portal, Day of Defeat, Team Fortress, Left 4 Dead and Dota.
Valve was founded in 1996 by the former Microsoft employees Gabe Newell and Mike Harrington. Their debut game, the first-person shooter (FPS) Half-Life (1998), was a critical and commercial success and had a lasting influence on the FPS genre. Harrington left in 2000. In 2003, Valve launched Steam, followed by Half-Life 2 (2004), the episodic sequels Half-Life 2: Episode One (2006) and Episode Two (2007), the puzzle games Portal (2007) and Portal 2 (2011) and the multiplayer games Team Fortress 2 (2007), Left 4 Dead (2008) and Dota 2 (2013).