Steam's concurrent users just hit a new all-time high of 18.8 million, the largest point in the last two years.
Even with the Epic Store's popularity, the Fortnite titan still hasn't dethroned Steam (and likely won't for a long time). As per SteamDB's findings, more Steam players are jumping online at once than ever before; roughly 18.8 million users played Steam at the same time, up from the previous 18.5 million record held two years ago. There's roughly 264,000 more users logged in at once now than two years ago, representing a 1.42% increase in concurrent users.
Steam's MAUs (monthly active users, a metric that shows a service's overall attraction rate) are pretty high and shows the platform isn't being jeopardized. In 2018, Steam had a tremendous 90 million MAUs with over half of those users signing in and playing every day. The Epic Store had 108 million customers in 2019, the company said, but no MAU metrics were given, and bear in mind the free monthly games are a big reason people sign in and use the store.
Valve has yet to deliver a Steam Year in Review for 2019, so we don't know how much those MAUs or DAUs have changed. But given the huge spikes attributed to Red Dead Redemption 2 and Halo: Reach, I expect those numbers to jump a bit.