https://www.gamespot.com/articles/pubg-is-closing-in-on-2-million-concurrent-players/1100-6453888/

At first it was seemingly unthinkable that Playerunknown's Battlegrounds would surpass Dota 2 and reach 1 million peak concurrent users on Steam. Well, the game has done that and it's not slowing down, it seems. The Hunger Games-style multiplayer game is closing in on 2 million peak concurrent users. The latest publicly available Steam data (via Kotaku) shows that the game had 1.96 million peak concurrent users today.

Steam data also shows that the service had 16.3 million concurrent users today, which means around 12 percent of the peak concurrent Steam users today played PUBG. Check out the chart below to get an idea about the margin by which PUBG is smoking every other game when it comes to peak concurrent users.