XP

Experience Points (XP) are a numerical quantity that dictates a player's level and one's progress in that level. The experience points are shown (in multiplayer) on the bottom of the screen with a yellow meter (excluding Black Ops). When a player gains experience points, the yellow moves further to right and resets when having achieved the next level.

The Experience Meter is only available in Call of Duty 4: Modern Warfare, Call of Duty: World at War, Call of Duty: Modern Warfare 2, and Call of Duty: Black Ops. Experience points are also available in Call of Duty: United Offensive but there is no experience meter and the ranks reset when one ends or exits a match.

Call of Duty: United Offensive
United Offensive was the first game to feature a pseudo-experience point system. Upon the start of each game, a player spawns as a Private with a limited amount of ammo and a single grenade. Points are accumulated from kills, flag captures, bunker destruction, and the like, with every ten points resulting in a promotion to a higher rank. Ranks and points do not carry on from game to game; they are reset for every game.

Call of Duty 4: Modern Warfare

 * Killing the enemy. The player gains 10 points per kill in Team Deathmatch (all forms) and Sabotage. 5 points are earned for killing in Free for All, Headquarters and Domination. The player can gain 50 points per kill in Search and Destroy, as no respawns are permitted; the life is worth more. Kills in Cage Matches are worth 20 points. If one kills when using Last Stand perk, double points will be earned. In Headquarters or Domination, a player can score an extra 5 experience points for killing an enemy who is within an objective capture range (i.e. within a Domination flag).
 * XP Stacking. The player has XP stack when earning xp in rapid succesion. For example, if a player kills 3 people in about less than one second in team deathmatch (Although this works in all modes), the player earns 10XP for every kill, and the xp that appears in the middle of the screen will continue counting past 10. example: kill a player, get 10 xp. kill two players very quickly, the xp onscreen will show 20. some players think that "xp stacking" means that the second kill would be worth 20xp the third kill would be worth 30xp etc. but this is not the case.


 * Assisting in the death of an enemy. If the player injures an enemy but does not kill that enemy and that player dies before their health is fully regenerated the player is awarded an assist, 2 experience points for matches which grant 10 exp a kill, 1 for kills which grant 5 exp a kill, 25 points in Search and Destroy, and assists are impossible to achieve in Free-for-all mode.


 * Completing challenges. Challenges are a new method to gain experience points. Challenges have some requirements to be fulfilled before the reward is available. For example, for marksman challenges, one needs to kill the enemy using the pertinent gun or in expert challenges, one would need to kill the enemy via headshots with the gun. There are also challenges that requires player to do other, more varied tasks, for example, the "think fast" challenge requires a player to kill an enemy by directly hitting the enemy with a Fragmentation Grenade. The challenges involving guns gives either attachments or camouflages as an addition to experience points. Other challenges give only experience points.


 * Additionally: The game gives some bonus points for the player's performance when the match ends as a "Match Bonus". The match bonus is based only on one's rank, the duration of the match and the gamemode. It does not, contrary to popular belief, include the amount of kills or deaths. So a player on the top of scoreboard can still get less match bonus than a person at the bottom.
 * As of the release of Modern Warfare 2, the player will permanently receive double XP on all kills, in all game modes, but on PS3 because Infinity Ward is too lazy to disable it.

Call of Duty: World at War
The player can gain experience points in the same manner as in Call of Duty 4: Modern Warfare, but also by:


 * Cooperative (Co-op) gameplay. This is a new mode where one can play the missions in normal gameplay but with 2-4 players. One can do exclusive challenges when playing in Co-op. Remember that in Co-op only the XP gained from Co-op challenges count for one's level, the XP earned in the Co-op missions for kills or objectives do not count. Playing Nazi Zombies does not gives any experience points. Playing in split screen cooperative mode also does not give any experience points


 * Completing vehicle challenges
 * Killing a dog: this gives 3 points in all game modes except Free for All (2 points) and Search and Destroy (not confirmed)


 * Reviving a teammate whom is using Second Chance. This gives the player 2 points.

For example in Team Deathmatch:
 * Gaining an assist. This is more complicated than Call of Duty 4: Modern Warfare as the amount of experience points gained is proportionate to the amount of damage inflicted towards the enemy. This is given in multiples of 5ths of the amount of XP given for a kill. The only exception is Search and Destroy, where all assists are worth 25 XP.

10 points for a kill.

2 assist points for at 1-39% of damage given.

4 assist points for at 40-59% of damage given.

6 assist points for at 60-79% of damage given.

8 assist points for at 80-99% of damage given, includes putting an enemy in Last Stand with a teammate "stealing" the kill.

Call of Duty: Modern Warfare 2
The experience system In Call of Duty: Modern Warfare 2 has been completely redone. Instead of just getting XP for kills, the player gets it for many different factors involving the kill such as:


 * Base Kill Award - 100 in Team Deathmatch and Sabotage, 500 in Search and Destroy, 200 in Cage Match (third person) and 50 in other modes.


 * Payback! - Kill an enemy who has killed the player previously. +50XP Getting this for a particular opponent will reset it until they kill the player again.
 * Buzzkill! - Kill an enemy who is 1 kill short of acquiring a kill streak reward. +100XP
 * Bulls-eye! - Kill an enemy with a throwing knife. +50XP Becomes 0XP at later levels.
 * Flag Runner! - Picked up the flag in a Capture the Flag match. +50XP
 * Stuck! - Stick a Semtex grenade to an enemy. +50XP
 * Rescuer! - Save a wounded teammate +50XP Kill the person attacking that teammate.
 * Hijacker! - Steal an enemy care package. +50XP Sometimes +100XP, later becomes 0XP
 * First Blood! - Be the first person to get a kill in a match. +100XP
 * Offense! - Kill a defender. +50XP In an objective game, kill an enemy who is near a point/flag they control.
 * Defense! - Kill an attacker while near a point/flag one controls in an objective game. +50XP (Does not matter if done by air support as long as they are near the player's own flag)
 * Comeback! - Recover from a streak of deaths. +50-100XP More dependent on amount of deaths in death-streak
 * Position Secure! - Take an objective. +150XP
 * Double Kill! - Kill two enemies in quick succession. +50XP
 * Triple Kill! - Kill three enemies in quick succession. +75XP
 * Multi Kill! - Kill four or more enemies in quick succession. +100XP
 * Longshot! - Kill an enemy from a distance. +50XP (Score a kill beyond the minimum damage range of a weapon that isn't a sniper rifle. Sniper rifles can also get longshots, shotguns cannot.)
 * Share Package! - A teammate saved the player's Care Package from the enemy! Multiples of 50XP depending on the number of kills usually required for the reward. (eg. a UAV will give +150 EXP, as it requires 3 kills to acquire normally)
 * One Shot One Kill - Kill an uninjured enemy with one sniper rifle shot. +50 XP
 * Flag Return - Return the flag. +50XP
 * Headshot - Kill an enemy with a bullet to the head. +50XP +500XP in Search and Destroy, despite saying +50
 * Crowd Control - Make an excellent distraction while a teammate kills the player shooting the shield. +50 for the assist, more for bullet damage absorbed by shield.
 * Afterlife - Kill an enemy while dead. +25XP (eg. Having Martyrdom equipped as a Deathstreak, killing the player's assailant with a dropped live grenade.)
 * Assisted Suicide - Injure an enemy before that enemy kills himself. +350XP
 * Execution! - Kill someone who is in Last Stand or Final Stand with a headshot. +100XP
 * Avenger - Kill an enemy immediately after they have killed a teammate. +50XP
 * Saboteur! - Plant the bomb. +1000 in S&D, +200 in Sabotage and +100 in Demolition.
 * Ninja Defuse - Defuse a bomb almost immediately after it has been planted (On Search & Destroy, Sabotage or Demolition). +1000XP
 * Hero! - Defuse the bomb. +1000 XP if in Search and Destroy, +100 if in Demolition, +150 if in Sabotage.
 * Heroic! - Get a capture point while in last stand. +200 XP
 * Assists give 200 XP in Search and Destroy and 1/5 of the base kill award on the rest of game modes.
 * Destroying a killstreak reward:+0 for Care Package Little Birds, +50 for UAVs and Counter-UAVs, +100 for Sentry Guns, +200 for Attack Helicopters, +300 for Harriers and Chopper Gunners, +400 for Pave Lows and AC130s.
 * Calling in a killstreak reward: +100 for 3-4 killstreaks (UAVs or Counter-UAVs), +150 for 5 killstreaks(Sentry Guns), +200 for 6-7 killstreaks (Harrier Airstrikes or Attack Helicopters), +250 for Emergency Airdrop, +300 for 9 killstreaks (Pave Lows), +350 for 11 killstreaks (Chopper Gunners or AC130's), +500 for EMP, +1000 for Tactical Nuke.

Call of Duty: Black Ops

 * Above and Beyond - +200 Capture a point while in Second Chance.
 * Afterlife - +100 Killed an enemy while dead.
 * Anti-Bomber - +100 Killed an enemy that was defusing.
 * Assist - +10-80 Injure an enemy and your teammate kills him. (Points vary depending on how much the player damages the opponent)
 * Assisted Suicide - +100 Injured an enemy that killed themselves.
 * Avenger - +50 Killed an enemy who recently killed a teammate.
 * Backstabber - +50 Knife an enemy player in the back.
 * Bankrupt - +10 Kill an enemy with the Tomahawk in Sticks and Stones
 * Bank Shot - +100 Killed an enemy with a banked Tomahawk.
 * Bomber - +100 Detonated the bomb.
 * Buzz Kill - +100 Stopped an enemy short of a killstreak, stopped an enemy bomb carrier, killed a flagrunner
 * Comeback - +100 Recovered from a death streak.
 * Defense - +100 Killed an enemy near the defense point.
 * Double Kill - +50 Killed 2 people in rapid succession.
 * Execution - +50 Kill a downed enemy with a headshot.
 * First Blood - +100 Got the first kill.
 * Flag Capture - +250 Captured the enemy flag.
 * Flag Return - +100 Returned the flag.
 * Flag Runner - +100 Pick up the enemy flag.
 * Hijacker - +50 Stole an enemy crate.
 * Longshot - +50 Killed an enemy from a distance.
 * Medic - +50 Revive a downed teammate that is using Second Chance Pro.
 * Multi Kill - +100 Killed more than 3 enemies in rapid succession.
 * Offense - +100 Killed an enemy near the objective.
 * Off The Air - +100 Took out a Valkyrie.
 * One Shot, One Kill - +50 Kill an enemy with one bullet.
 * Payback - +50 Killed the enemy who killed you.
 * Position Secure - +150 Took an objective.
 * Rescuer - +50 Saved a wounded teammate.
 * Road Rage - +100 Took out an RC-XD.
 * Saboteur - +500 Planted the bomb.
 * Scalper - +50 Killed an enemy with a Tomahawk.
 * Share Package - +50 Let a teammate take your Care Package.
 * Skewer - Shot and killed an enemy with the Ballistic Knife.
 * Scrapped - Brought down a Helicopter, Spy Plane, or Counter-Spy Plane. (+150 for Spy Plane and Counter-Spy Plane, +400 for Care Package Helicopter, +500 for Chopper Gunner)
 * Scrapped Assist - +50 Assisted in taking down air support.
 * Stuck - +100 Stick an enemy with an explosive.
 * Triple Kill - +75 Killed 3 people in rapid succession.
 * Turret Kill - +100 Took out an enemy turret.

Video
thumb|left|300px|Rank-Up differences on different consoles.