“Stardew Valley now supports up to four-player co-op,” the game’s creator explained. “Co-op is nearly identical to single-player, but with one to three other friends playing together with you to achieve a common goal. Any single player game can be ‘converted’ to a co-op game by having Robin build one or more cabins on your farm. One player serves as the host, and the other players connect to the host in order to play. Therefore, the host must be in-game at all times when the group wants to play.”
Update 1.3 wasn’t just about multiplayer; the patch also added a new traveling festival, a winter mystery, additional character events, skull cavern changes, the ability to swap professions, craftable signs, more outdoor decorations, an auto-grabber, indoor garden pots, and (most importantly) hats on horses.