Introduced in the Version 0.97.0 build of Super Animal Royale alongside the release of the Xbox One and Xbox Series X|S port, Crossplay allows PC/Steam players and players on Xbox One and Xbox Series X|S to play together in the same matches.
Steam players automatically have the enable crossplay feature on at all times, where as the Xbox One and Xbox Series X|S players must toggle it on in order to be able to connect into the same games as PC players.
Players on Xbox One and Xbox Series X|S are not able to invite players on the Steam/PC version into parties or matches. In order to play in the same matches, all players would need to select the same game mode, and server and attempt to join at the same time. Pixile has confirmed that they are currently working on a way for Steam players and Xbox players to be able to join each others parties. Details to be added upon any developments of this.