https://www.polygon.com/2017/12/29/16829768/pubg-3-million-concurrent-players-record

Playerunknown’s Battlegrounds, the survival shooter that has emerged as the most popular PC game of the year, has just beaten its own record for most concurrent players.

Early this morning Battlegrounds eclipsed 3 million players. Steam itself put the number at 3,106,358 exactly.