First game to have more than one million Steam players online

Being the most actively played game on Steam, it perhaps won't come as a surprise that free-to-play MOBA Defense of the Ancients 2 (DotA 2) was also the first game to break the one-million threshold for concurrent users. A total 1,075,464 players logged on to play DotA 2 on 15 February 2015. This is some way short of rival League of Legends, though, which has had a peak of more than 7.5 million concurrent users, contributing to its record for the most played action real-time strategy videogame.