Dota Auto Chess, a custom game inside Dota 2, continues experiencing enormous success, garnering a playerbase much larger than most games on Steam.

The game recently surpassed a brand-new milestone: 300,000 concurrent players, and is currently sitting at over four million total subscribers. This is a sign of the mod’s continued growth, as only last month the game was sitting at over 100,000 concurrents and nearly 700,000 subscribers, according to esports outfit Team Secret’s director of operations Matthew Bailey.

This makes the mod itself one of the most popular games on Steam. If you were to rank Auto Chess on Steam’s official player statistics rankings across all games on Steam, it would place fourth, putting it ahead of the Steam playerbases for Rainbow Six Siege (the game is also available on consoles and through Ubisoft’s own store on PC) and Grand Theft Auto V (which is also available outside of Steam through the Rockstar Social Club store), and behind Steam exclusive Counter-Strike: Global Offensive, which sports more than twice the concurrent playerbase.

Of course, much of this is off the back of Dota 2’s nearly million-strong concurrent playerbase, but that the mod has seen nothing but growth in the past month bodes well for its success, as developer Team Drodo continues to update the game and makes money through in-mod microtransactions.

If you’re curious about what the heck all this Auto Chess business is all about, check out our recent primer on the mod.