Korean publisher NCsoft has announced that its popular MMO PC series Guild Wars has passed the six million unit sales mark just days ahead of its fourth birthday on April 28th.

Unlike most traditional MMOs, Guild Wars if free-to-play, so whilst gamers have to pay for each expansion they do not have to pay a monthly subscription to play the game online.

“We are humbled by how gamers have responded to Guild Wars over the past four years, and we are proud that the game and its community have helped to continually shape, define, and expand the genre,” ArenaNet studio head Mike O’Brien said.

“Our subscription-free business model has proven to be a big hit with gamers, bringing an enormous and diverse online community to the game.”

First released in 2005, Guild Wars has gone on to spawn three expansions – factions, Nightfall and Eye of the North. Guild Wars II has been in development for some time, but its release date remains TBC.