Players drop their dogtags upon death, appearing bright yellow for the killer's team and as bright red for the victim's team. The player's team gets a score for confirming the kill by collecting the dogtags, which awards the killer 50 XP (alongside the XP rewarded from the kill) as well as the player who confirmed it. The player may also deny teammates' deaths in the same fashion for the same 50 XP (250 XP if the tags were the player's own), but denying a kill does not add to the team score. However, it prevents the enemy from confirming it. Collecting a dogtag does not contribute to the player's Pointstreak.
By default, 65 tags are required to win. Alternatively, the team which has most tags if the time runs out wins. The tags disappear if they are not collected quickly enough, or if the player who dropped them either dies again or quits the game.
Dog Tags in Modern Warfare 3. Note that the dog tags say "Simon "Ghost" Riley".
Kill Confirmed reappears in Call of Duty: Black Ops II as it did in the previous installment, with slightly changed settings. Similar to Call of Duty: Modern Warfare 3, enemies drop dogtags that appear bright yellow upon death, which provide a score for the team if collected, known as confirming the kill. If a teammate drops a dogtag, it appears as bright red, and if collected, the kill is denied, which prevents the enemy from confirming it. However, the player now gets 50 points for killing an enemy and 100 for confirming a kill, both of which will go towards the player's scorestreak. If a teammate confirms it, the player who killed the enemy gets 25 points. Denying the kill gives 25 points, and if the dogtags were the player's own, a Retrieved medal is awarded. Additionally, the dogtags do not disappear if not collected quickly enough, and 100 confirms are required to win.
Dogtags in Call of Duty: Black Ops II multiplayer. Note that the tags say "VIKTOR REZNOV".