The picks that combine couch and online
Borderlands 3 is the clearest example on any platform, which is why it leads. Two people play split-screen on one console and take that session online with two more friends, giving you a four-player campaign from two machines. It is a finished game with an ending, it is usually cheap, and there are no seasons to fall behind on. The one hard limit is crossplay: everybody online has to be on the same platform family. Full detail in the Borderlands 3 review.
Diablo IV is the same trick with the opposite trade. Two-player split-screen on console, and then full crossplay and cross-progression online - so the couch pair can join friends on PS5, Xbox and PC in one session, and either of them can pick the character up on a different device later. The cost is that it is a live-service game that expects regular attention. Review here.
Minecraftis the most flexible of the three. Console split-screen takes up to four players on one machine, and that world - or someone else's - is shared with anyone on Bedrock, which means phones, Switch, PlayStation, Xbox and PC. For a mixed group where half the people are in one room and the rest are anywhere at all, nothing else covers as much ground. Buy the console or mobile version, not Java: our review explains why that distinction costs people money.
The split-screen-over-the-internet trio
It Takes Two, Split Fiction and A Way Outare two-player-only story games where the split frame is the design rather than a compromise, and it stays split whether you are on one sofa or a thousand miles apart. All three include a Friend's Pass, so one purchase covers both players. Split Fiction adds crossplay, which the other two lack - if your partner in this is on a different platform, that is the deciding factor, and the comparison lays it out.
Portal 2 belongs in the same family and costs a fraction as much: a purpose-built two-player campaign, playable split-screen or online, and one of the best co-op games ever made. Same-platform only, and in practice a PC game today.
The local-first picks that still go online
Overcooked! All You Can Eat is the party pick that does both formats with full crossplay online - four people in a kitchen, or four people on four different systems. Sackboy: A Big Adventure covers two-to-four local or online co-op for a gentler group, though with no crossplay listed treat online as same-platform. Human: Fall Flat is the cheap one, with crossplay online and local play on top.
Working out which shape your group needs
Count the machines, not the people. Four friends with four consoles want plain online co-op and should start at the crossplay hub. Four friends around one television want the couch co-op page. It is the in-between case - two machines, four people - where this page earns its keep, and it is far more common than the industry designs for.
If you already know the platform, the shortlists are broken out by machine: split-screen on PS5, split-screen on Xbox, and split-screen on PC, which is the hardest of the three and explains why.