DayZ, the zombie-focused mod for ultra-realistic shooter Arma 2, has reached the 500,000 user milestone, the dev's Twitter account revealed today.

"Congratulations everyone, with your support through tough times, mistakes, troubles, and technical problems, we now have over 500k users," the tweet revealed. The 'Alpha Version' of DayZ, which requires Arma 2 and its standalone expansion Operation Arrowhead, was released in April 2012.

Speaking earlier this week at the indie-focused event, Rezzed, mod creator Dean Hall said his free mod will soon eclipse sales of Arma 2 at the rate it's being downloaded.

"Currently we're running 22,000 concurrent at full peak, and 10,000 off peak, which is pretty huge numbers considering the original data structure and system was designed to handle 100 concurrents, and two servers," Hall said during his talk, according to Eurogamer.

Hall, who works for Arma developer Bohemia Interactive, revealed that an estimated 400,000 users had experienced the mod by Friday, July 7, and noted an average of about 10,000 new users were jumping into the fray each day.