The official Sonic Superstars website seems to have confirmed that Superstars' cooperative multiplayer will be local-only and that the game won't feature online multiplayer functionality.
One of the big reveals at Summer Game Fest last night was Sonic Superstars, a new 2D title that features a new aesthetic for the series and even brings back some fan-favourite characters like Fang the Sniper. Excitingly, it also features cooperative play for up to four players, which is a first for the series - unfortunately, it seems like co-op is going to be limited to local play only.
The official reveal trailer for Sonic Superstars noted that players could "team up with friends", but didn't mention whether that would be through online multiplayer or local co-op. Considering most games nowadays focus on having online multiplayer, it was an easy assumption to think that this would be the case for Superstars.
That doesn't seem to be true, however. The Sonic Superstars website just went live after the game's reveal, and it breaks down some of the game's unique mechanics, including some of the new abilities and being able to play as Sonic, Knuckles, Amy, and Tails. One section breaks down the game's multiplayer, seemingly confirming that it's local only.
It reads, "More Friends, More Fun. For the first time in a Sonic game, play through the entire campaign with up to 3 other players with drop-in and drop-out 4-player Local Co-op". A press release shared by Sega also notes that the game "offers local 4-player co-op, so fans can play solo or cooperatively with friends through the entire campaign", again making it clear that it's local-only.
Although these statements do at least confirm that co-op is drop-in and drop-out, it's a shame that one of the game's biggest draws will be limited to local play. In fairness, the trailer didn't say that co-op would be online but, as we said above, it's a fair assumption to make in 2023 unless specifically told otherwise, which the trailer also didn't do.
That being said, online multiplayer in a 2D Sonic game does seem like it'd be quite hard to implement, as all players need to be going at around the same speed to keep the screen focused on everyone at once. That already seems like it's going to be tough to manage when four players are watching on one score, let alone with everyone playing on different consoles across the world. Sega hasn't commented on why the game is specifically focusing on local multiplayer only, but we'd wager a guess that it's something to do with that.