It's no secret that PlayerUnknown's Battlegrounds is a tremendously popular game. It sold a million copies less than a month after going into Early Access, and three months later had pushed that number to five million. And earlier today it set another big milestone by breaking 500,000 concurrent players on Steam.
Today's peak actually climbed even higher, to a total of 523,436, before slipping to a little under 430,000 at the time of writing. That rapid climb up the ranks makes me wonder if Dota 2's position at the top of the heap is as unassailable as it seems to be. PUBG may be struggling to work out some issues with disaffected players, some of them legitimate and others just hilarious, but it's clearly a beast, and as it continues to be refined and expanded that player count is bound to keep growing. I don't think it will ever supplant Dota 2 at the top (Dota 2 is pretty big stuff, after all), but Grimoire: Heralds of the Winged Exemplar came out today, so what do I know?
PUBG recently rolled out first-person-only servers, and it sounds like that could help push the game to even greater heights: "An arguably minor change [that] has made Battlegrounds a more tense, more rewarding game overnight," as we put it on our analysis of the new POV. That update apparently caused server lag issues for some players, but a hotfix has since been rolled out that should clear up the problem.