Persistent Upgrades, also known as "Perma-Perks", are unlockable upgrades that the player(s) can gain through unique methods. These upgrades only take effect and can be acquired on Green Run, Die Rise, and Buried (although only in their main modes; upgrades are absent from submaps such as Grief in Borough). The player can have multiple upgrades at once, and they carry over to different game sessions and maps. They can also easily be lost, usually if the player does not make use of the upgrade.
When an upgrade is obtained, a green haze (similar to picking up a Power-Up) appears near the player, and the player's character will say a line about it. Losing one will result in a faint eerie sound.
Persistent Upgrades can't be obtained nor will they be affected when playing in Local or LAN Party.
List of Upgrades
The player can earn revive twice as fast by reviving downed allies seventeen times in one game. This effect can be stacked with Quick Revive.
To lose it, the player must try and fail to revive a downed person, even if said person is later revived. Even an accidental fail (such as being knocked out of the way) will cause the upgrade to be lost.
More Headshot Damage
The player can earn increased headshot damage by getting an arbitrary amount of collateral headshots (multiple headshot kills with one bullet). In addition to increased headshot damage, shooting a zombie anywhere will make its head pop, although this effect is aesthetic. Sometimes the green flash will show in Survival on any of the survival maps, though the persistent upgrade will not be applied.
To lose it, the player must kill twenty five to seventy five zombies in a row without a headshot.
The player can earn stronger barriers to be built on windows by repairing seventy five barriers in one game. The barriers are partially made of steel and screwed in, so it will take more time for them to be taken down.
This upgrade will not take effect and cannot be earned before round ten.
To lose it, the player must fail to build a single barrier in a round.
Stronger Carpenter Barriers
The player can earn reinforced barriers for Carpenter to build by killing a zombie trying to come out of a barricade meanwhile the Carpenter is boarding the windows. The effect is separate from the stronger barricades above, and can be earned and lost without either affecting another.
To lose it, the player must fail to kill a zombie trying come out of a barricade during a Carpenter, regardless of if there are any.
The player can earn 200% Health, with a down resulting after four hits instead of two. The effect stacks with Juggernog, allowing the player to have a maximum of 300% health. This upgrade is obtained when the player is downed without Quick Revive (thereby ending the game) three times.
On Buried, the upgrade is obtained by completing Round 1 in processing, then getting downed by zombies (still in processing).
This upgrade is automatically lost at the start of round fifteen.
The player can earn a subversion of Insta-Kill by not killing a single zombie during an Insta-Kill, twice in a row (though it will rarely be obtained from just one). The effect lasts fifteen seconds, is activated when an Insta-Kill is obtained and allows the player to simply walk into a zombie to kill it. Killing a zombie using it will only give fifty points.
To lose it, the player must be damaged by a zombie during the Insta-Kill (with the exception of a flaming zombie exploding).
Refund on Perks
The player can earn an upgrade to give one thousand points when going prone in front of a Perk-a-Cola machine after buying said perk. This upgrade is obtained by going prone each time you buy the perk approximately sixty five times.
The player must go prone after the perk appears on the screen and then has five seconds to go prone.
To lose it, the player must not go prone in front of a Perk-a-Cola machine after buying it.
Mystery Box Upgrade
The player can earn an upgrade to decrease the chances of getting "bad" weapons from the Mystery Box. This upgrade is obtained when the player takes a random amount of weapons from the Mystery Box. They must keep taking whatever gun they earn. The player will see a glow and a teddy bear will appear on the box.
This upgrade cannot be earned after round ten.
This upgrade is automatically lost at the start of round ten.
The player can earn an upgrade to gain the effect of PhD Flopper. This upgrade is obtained when the player takes a certain amount of fall damage (enough to turn the screen red briefly) five to ten times. Unlike PhD Flopper, this upgrade does not protect against overcooked frag grenades.
This upgrade is only available on Buried.
To lose it, the player must take significant fall damage (around 80-90) by falling without dolphin diving.
The player can earn an upgrade to reduce all purchase costs by half during a Double Points Power-Up. If the player does not have enough money to purchase the item even with Half-off, it may take an even smaller amount. This upgrade is obtained when the player accumulates three thousand or more points during a Double Points Power-Up.
To lose it, the player must fail to spend at least one thousand points during the next Double Points.
The player can earn an upgrade to give twice the points you would normally earn. This upgrade is obtained by only getting a random amount of headshots or melee kills only during a Double Points Power-Up.
To lose it, the player must kill a zombie with melee or a headshot at any time.
The player can earn an upgrade to retain all of their perks except Quick Revive after being downed and revived by Quick Revive or another teammate, being revived by the Pack-a-Punched Ballistic Knife will cause all perks to be lost but not the upgrade. This upgrade is obtained when the player buys four perks before round four.
In a game with two or more players, the player will retain all of their perks except for their last obtained perk. Quick Revive will always be lost first, however.
To lose it, the player must go down three times in a row without any perks.
Extra Sniping Points
The player can earn an upgrade to give an extra three hundred points with each kill made using a sniper rifle. This upgrade is obtained when the player gets five to fifteen long range kills using any sniper rifle.
To lose it, the player must miss three shots in a row with a sniper rifle.
Double Pistol Points
The player can earn an upgrade to give double points from shots fired from a pistol. This upgrade is obtained when the player fires all rounds from a pistol without hitting a single zombie, then kills one to three zombies with melee.
To lose it, the player must kill one to ten zombies with melee or a pistol.
Ray Gun Off The Wall
The player can only obtain this upgrade if they are rank three or lower and they have two or less tally marks.
This upgrade is automatically lost between round twelve and fourteen.