Hardcore

Hardcore mode is an alternative to the normal playlists in Call of Duty 4: Modern Warfare, Call of Duty: World at War, Call of Duty: Modern Warfare 2, Call of Duty: Black Ops, Call of Duty: Modern Warfare 3 and Call of Duty: Black Ops II. As the name suggests, the gameplay is much more testing and realistic, with the following implications:
 * Significantly less health - Players can only withstand 30 damage before dying or going into Last Stand/Final Stand/Second Chance/Dead Man's Hand mode. This practically makes every weapon kill in one or two hits.
 * Limited HUD - The player's HUD is limited to certain objective related things, such as objective markers and whether the player has an enemy flag in Capture the Flag for example. Green names are also seen above teammates, but the red text on enemies is absent. Normal HUD features such as the mini-map, ammo counter and equipment slots are missing. The minimap will be available for the duration of a UAV (and its other variants). In some games, the map is available without it in the pause menu as well. In the hardcore Wii version of Call of Duty: World at War, there is a white dot used as a reticle in the game. In Modern Warfare 2, all notifications (upper right corner of the screen) of players calling in or destroying killstreaks, achieving match targets or other notifications such as triple kills are disabled, with the exceptions of enemy players copying their class or destroying their tactical insertion.
 * Friendly Fire on - Teammates can be damaged and killed. Deliberate team-killers are punished; in Call of Duty 4: Modern Warfare and Call of Duty: Modern Warfare 2, a player is automatically killed and sat out for a period of time after 3 or more team-kills (in the latter, certain actions such as killing the team with a launcher in the start of a round can lead to much harsher penalties). Additionally, a player-controlled Killstreak ends prematurely if the penalty is given. In Call of Duty: World at War, Call of Duty: Black Ops and Call of Duty: Black Ops II the player is automatically kicked out of the game (and is banned from joining the session) after three team-kills. Some Killstreak/Scorestreak kills do not count towards a kick, a notable example being the Warthog.
 * In Call of Duty: Modern Warfare 2 and Call of Duty: Modern Warfare 3, an option called Hardcore Ricochet is available, which replaced most of the Hardcore playlists. Friendly fire is still enabled, but in the matter that the damage done to teammates is inflicted towards the player with no damage done to the teammate shot.

In Call of Duty 4: Modern Warfare

 * Hardcore Team Deathmatch
 * Hardcore Search and Destroy
 * Hardcore Headquarters

In Call of Duty: World at War

 * Hardcore Team Deathmatch
 * Hardcore Search and Destroy
 * Hardcore War
 * Hardcore Headquarters
 * Hardcore Free-for-All
 * Hardcore Capture the Flag

In Call of Duty: Modern Warfare 2

 * Hardcore Team Deathmatch
 * Hardcore Capture the Flag
 * Hardcore Ricochet: S&D
 * Hardcore Ricochet:HQ Pro
 * Hardcore Mosh Pit

In Call of Duty: Black Ops

 * Hardcore Team Deathmatch
 * Hardcore Search and Destroy
 * Hardcore Free-for-All
 * Hardcore Headquarters
 * Hardcore Capture the Flag

In Call of Duty: Modern Warfare 3

 * Hardcore Ricochet: Team Deathmatch
 * Hardcore Ricochet: Search and Destroy
 * Hardcore Ricochet: HQ Pro
 * Hardcore Ricochet: Kill Confirmed
 * Hardcore Ricochet: Domination
 * Hardcore Free for All

In Call of Duty: Black Ops II

 * Hardcore Team Deathmatch
 * Hardcore Search and Destroy
 * Hardcore Capture the Flag
 * Hardcore Kill Confirmed
 * Hardcore Domination

Trivia

 * In Call of Duty: World at War, Call of Duty: Black Ops and Call of Duty: Black Ops II, when the player is kicked for killing many teammates, the announcer will make an insult towards the player (such as Get that son of a bitch out of my sight! or I'm sick of this asshole, get rid of him!).
 * Call of Duty: Modern Warfare 2 originally featured Hardcore mode for all playlists, but it was cut because of dedicated servers removal.
 * In Call of Duty: Modern Warfare 2, players often use the Heartbeat Sensor attachment as an alternative to the mini-map.
 * In Call of Duty: World at War, Call of Duty: Black Ops and Call of Duty: Black Ops II, the player is not kicked for teamkilling if they are the host. However, in the first of the three, the player will not be able to spawn in a period of time as a penalty.
 * In Call of Duty: Black Ops II it is notable that the players' characters do not speak in Hardcore mode like they do in Core mode (ex. Saying "He's down" upon getting a kill or yelling "Frag Out" upon throwing a grenade). In fact, the characters do not even so much as make a sound when killed. The reason for this is currently unknown.
 * In Call of Duty: Black Ops II, an update replaced Hardcore Capture the Flag with Hardcore Domination.