Multiplayer first person shooter games for PC/Windows with 4-player support

Serious Sam: The First Encounter

Players: 4 local, 16 online

DOOM 3: OpenCoop (Mod)

Players: 0 local, 4 online

Call of Duty: World at War

Players: 0 local, 4 online

Halo Infinite

Players: 0 local, 4 online

ORION: Prelude

Players: 0 local, 5 online

Borderlands: The Pre-Sequel

Players: 0 local, 4 online

Killing Floor 2

Players: 0 local, 6 online

Verdun

Players: 0 local, 4 online

Back 4 Blood

Players: 0 local, 4 online

Star Wars Battlefront II (2017)

Players: 0 local, 4 online

Unfortunate Spacemen

Players: 0 local, 10 online

Halo: The Master Chief Collection

Players: 0 local, 4 online

Serious Sam 2

Players: 4 local, 6 online

Quake

Players: 0 local, 16 online

Shadow Warrior 2

Players: 0 local, 4 online

Serious Sam: The Second Encounter

Players: 0 local, 16 online

PAYDAY 2

Players: 0 local, 4 online

ArmA II

Players: 0 local, 4 online

Close Combat: First to Fight

Players: 0 local, 4 online

Contagion

Players: 2 local, 8 online

Killing Floor

Players: 0 local, 6 online

No One Lives Forever: Spy in HARM's Way

Players: 0 local, 4 online

Object N

Players: 0 local, 4 online

Generation Zero

Players: 0 local, 4 online

Call of Duty: Black Ops Cold War

Players: 0 local, 4 online