This week's PlayStation 4 launch of Final Fantasy XIV: A Realm Reborn has helped push the MMO pass the 2 million mark for registered accounts, a rather large bump from previous numbers.
Square Enix hasn't given any hard numbers on just how many of those registered users are actually playing the game, but we do know that six months ago the number was at 1.5 million registered users. Meanwhile, a trailer from February proclaimed the second-iteration MMO had "over 1.8 million adventurers."
It's worth noting registrations do not equate to active subscribers, although the base game does require a purchase and includes the usual 30 days of free game time. According to a translated 4Gamer interview
with Director Naoki Yoshida, in March around 500,000 people were logging into A Realm Reborn each day. It is unclear as to whether that amount is still steady, but hopefully hard numbers will come out during the next quarterly report from Square Enix.