https://www.polygon.com/2019/1/14/18182370/rocket-league-crossplay-ps4-switch-xbox-one-pc

Rocket League players can now battle each other regardless of the system they’re playing on. Developer Psyonix rolled out cross-platform play support for the vehicular soccer game Monday across Nintendo Switch, PlayStation 4, Windows PC, and Xbox One.

Psyonix and Sony added Rocket League to PS4’s cross-play beta program today, an initiative that launched in September, in large part thanks to Fortnite and player outcry. Cross-platform play is now available in all of Rocket League’s online match types, including casual, competitive, and extra modes.