Most gamers would recognize Epic/Psyonix's Rocket League as an institution at this point - despite launching in July 2015, the game remains famous in April 2021. Many other popular multiplayer games have launched in that timespan, among them behemoths like PUBG and Fortnite. That raises the issue of just how popular Rocket League is in hard numbers, particularly for newer players worried about finding teammates.
The basics of Rocket League are simple: two teams, up to four players each, play soccer with rocket-powered cars. There are both single-player and multiplayer modes, but the focus is on the latter, moreso with the shift to a free-to-play model which means Epic is now selling loads of cosmetic DLC. The simple inputs and family-friendly nature of the game remove any age barriers, while simultaneously allowing easy cross-platform competition across PC, PlayStation, Xbox, and Switch. Indeed, some kids have likely been playing Rocket League since they were old enough to understand a controller.
Rocket League's multiplatform spread makes it difficult to gauge exact figures, but there is some concrete data. In September 2020, Rocket League officially crossed 1 million simultaneous online players. Epic also revealed that the game had topped 75 million players in total - how many of those still touch the game is uncertain, however, since it's entirely possible for someone to play once and leave forever while still holding an account.
What Unofficial Rocket League Player Counts Report
Data compiled from multiple sources by activeplayer.io indicates that an average of 90.5 million people were playing Rocket League at some point during March 2021, with a maximum of about 5.2 million per day. Nearing 5 PM Central time on March 31, the site's live player tracker registered anywhere between 205,000 and over 290,000 people across all platforms - a number likely to climb higher during the night. Steam Charts claimed 82,417 people were online in Rocket League around the same time, which isn't half-bad for Valve's store given that Epic discontinued sales there after taking over Psyonix. The only option for downloading the PC version of Rocket League now is the Epic Games Store.
Unfortunately, there aren't any easy ways to calculate Rocket League's player counts by hardware ownership. This may be by design - not just because Rocket League has a shared player pool, but because doing so might reveal that some platforms are less popular than others. Console makers are notoriously reluctant to enable unflattering statistics. With that said, it's safe to say Rocket League is still doing well, with plenty of matches to go around regardless of platform.
Sources: activeplayer.io, Steam Charts