It’s not supported in Halo 5
Halo 5: Guardians dropped split-screen cooperative play, a series staple, in favor of maintaining a smooth frame rate. The game does support online co-op, but it’s just not the same. We’ve grown so accustomed to going through these campaigns with our buddies in the same room.
Speaking to GamesRadar, franchise director Frank O’Connor admitted the resulting feedback from fans has been “huge,” but “realistically, for Halo 5, it’s not something we can just throw in a patch.”
“Split-screen is fun for me too,” he said. “It’s not something that I object to, and we would’ve loved to put it in. We’ll talk about it for the next game, and we’ll talk about it for the future.”
Halo 5 doesn’t, and won’t, have splitscreen – but Halo 6 might [GamesRadar]