The ones that surprise people most
Stardew Valley is the number one shock on this list. It is on every platform, it has four-player co-op, and the multiplayer is same-platform only - so a group with two people on Switch and two on PC cannot share a farm. If a calm co-op farm is what you want across platforms, Minecraft or Terraria are the substitutes. Our review covers the catch in full.
It Takes Twois the best co-op game ever made and it does not crossplay. The Friend's Pass means only one of you buys it, which people reasonably assume implies cross-platform play - it does not. Both players need to be on the same platform family. Its successor, Split Fiction, is the same design with crossplay, and that is the one to buy for a mixed pair. The comparison is built around exactly this decision.
Borderlands 3 catches out loot-game groups. Four-player co-op, split-screen on console, huge value - and no crossplay at all. Diablo IV is the crossplay alternative in that genre, at a higher price and with seasons attached; the head-to-head covers which is right for your group.
Mario Kart 8 Deluxe and Super Smash Bros. Ultimate are the exclusivity cases. Nothing is missing from them - they are simply Switch games, and a friend on an Xbox has nothing to install. For a mixed group that wants racing or fighting energy, Rocket League is free with full crossplay and is the closest thing to a universal substitute.
Grand Theft Auto V Online keeps players within the same platform and generation, which also catches out groups where one person is on older hardware. Elden Ring Nightreign matchmakes per platform, so a trio has to line up first - and it is a three-player game, which our three-player page covers. Portal 2 and A Way Out are both same-platform co-op, both excellent, and both worth buying if you have already matched platforms.
Deep Rock Galacticis the partial case worth understanding, because it is the shape a lot of games take - and because the line falls in a place nobody expects. Ghost Ship's own crossplay page says the Xbox and Microsoft Store versions play together and that the Steam version does not support cross-platform play, with PlayStation separate from both. So it is one of the best co-op purchases on this site for a group on Xbox and the Microsoft Store, and silently the wrong one if somebody bought it on Steam or is on a PS5. Our review spells out the pools.
The rule that prevents all of this
Ask what everyone is playing on before the group picks a game, not after. Most bad multiplayer evenings are not a bad game - they are a good game that one person could never have joined, chosen by four people who never checked.
If you already know the platforms, our crossplay combination pages are the fastest filter: PS5 and PC, Xbox and PS5, PC and Xbox, Switch and PC, Switch and PS5, Switch and Xbox, and phone and console. Everything on those pages has been checked against the developer's own listing.
And if a party will not connect in a game that does support crossplay, the cause is usually a setting rather than the game - our crossplay setup guide walks through the toggles on each platform.
The kart racers are the clearest case on this page - neither Mario Kart has ever crossed platforms - and the substitute is a single game. Sonic Racing: CrossWorlds seats four on one screen and crossplays across PS5, Xbox, PC and Switch, which is why it is the name we give every mixed group that asks for Mario Kart.