Split Screen is an option available for the Call of Duty games for both the PlayStation 3 and the Xbox 360. It is also available on Call of Duty: World at War's multiplayer and campaign modes. Call of Duty: Black Ops and Call of Duty: Modern Warfare 3 allows online multiplayer split screen support on the Xbox 360 and PS3 for the first time since Call of Duty 3.
Split screen allows multiple players to play on one screen. It divides part of the screen for each of the player. Split screen is featured in Call of Duty 2, Call of Duty 3, Call of Duty 4, World at War, Modern Warfare 2, Black Ops, Modern Warfare 3, and Black Ops II . With two people, the screen is split in half, either vertically, or horizontally. With three people, the screen is divided into two quarters, and one half. Two players get a quarter of the screen, while a third player gets half. With four players, the screen is divided into four quarters, one for each player. The offline split screen for Black Ops has the ability to play with bots. The difference between playing in split screen and Combat Training is the ability to have everything unlocked, including the prestige items. However, the player(s) cannot rank up.
When using split screen online, only one additional player can play, allowing two players to play on the same account. The screen is split in half horizontally, both players can rank up, but it only applies to the main player. When the second player signs out and signs back in, they'll start from the main player's current level, not from where they last ranked up.
The Negatives of Online Split ScreenEdit
The only issue online split screen solves is allowing one additional player to play along with the main player. There are many more problems that this feature causes that only hinders the player's (s') ability to perform well in-game.
- Vision is cut in half due to the two players sharing the same TV screen. Acquiring distant targets, especially when sniping, will be more difficult, as everything will appear half their normal size because of this. It will be extremely difficult to take out an enemy that is head glitching.
- Playing as two players means double the noise that occurs in-game. Listening for enemy movement, especially when using Sitrep, will be more difficult due to the conflicting sounds from the other player's half of the screen. It would also be difficult to tell which direction the enemy fire is coming from, thus be more likely to fall victim to flanking attacks.
- Boosting/Cheating in Infected : The main player will start off as a Survivor and hides in a common, hard-to-reach spot. All the while the second player gets Infected and blocks the path leading into the room where the main player is hiding/camping - doors, stairways, etc. and places their Tactical Insertion exactly where the stand to ensure they permanently stay in that spot. The main player/Survivor will either shoot through penetratable walls, killing the other Infected desperately trying to reach him, and get kills to illegitimately get a MOAB, or just simply wait out the time and illegitimately win the game. Another method is the main player will keep killing the second player, who continually places their Tactical Insertion wherever the main player can easily shoot them and rack up kills or earn a MOAB. This is frowned upon within the COD community. 
- Only Call of Duty: Modern Warfare 2 and Call of Duty: Modern Warfare 3 currently have the only offline split screen mode in which players can rank up. In Call of Duty: Black Ops and Call of Duty: Black Ops II, everything is pre-unlocked, and you can not change the game options. Both Call of Duty 4: Modern Warfare and Call of Duty: World at War use pre-made classes.