Bugs

Bugs (or Glitches) are errors, flaws, or failures in a computer program that causes it to produce an incorrect or unexpected result, or to behave in unintended ways. Most bugs arise from mistakes made in either a program's source code or its design. Bugs are normally patched by developers, so a very well-known bug won't exist for long.

In Left 4 Dead, the most notorious bugs are exploited to gain achievements or Versus advantage. This page is meant to provide a comprehensive list of currently known bugs for both games.

Left 4 Dead

 * In the first chapter of No Mercy, when playing as the Infected in Versus Mode, there is a military vehicle protruding through the wall of the apartments on the bottom floor. If you go within a few feet of the vehicle, you die instantly for no apparent reason and Tanks will constantly take 400 damage. This also applies for Survivors. The vehicle is commonly referred to by players as "The Killer Jeep", although the vehicle is technically a Humvee.
 * If a Survivor is standing next to an object that cannot be moved, and a Tank punches them into the object, the Survivor will get stuck. The Survivors will not be able to use any guns, or items while stuck. The only actions possible are spinning in circles and turning your flashlight on and off. It is possible to be freed by being pounced by a Hunter or getting incapacitated (you will teleport back to the other survivors after a set amount of time).
 * Near the end of The Sewer, the AI will sometimes get stuck next to the manhole, and be unable to move away from it.
 * At the final chapter of No Mercy (Rooftop Finale) when a Survivor is standing above the pipe near the minigun and Smoker drags him/her down the pipe he/she might actually be pulled above the electric generator but will be stuck between the two circles, not being choked and not taking damage. This glitch is very rare.
 * If a Tank is attacking players in Co-op mode, and they hide in the Safe Room, and one of them crouches and stays right behind the Safe Room door, the Tank won't be able to break the door, and will be stuck beyond it - swinging his fist - but not doing any damage to the player sitting behind the door, thus allowing an easy kill by shooting through the door.
 * It is possible to launch yourself from a minigun as a Survivor if you jump behind it and quickly mount and dismount it. Survivors usually won't move too far away, but if done properly, it may be enough to e.g. fall from the roof of No Mercy hospital when playing Versus/Survival version of map.
 * In the Crash Course DLC (possibly other campaigns, untested), in Versus mode, Special Infected can be killed by shooting where they are standing (during spawn period) before they have spawned.
 * In the Xbox 360 version (possibly PC version as well), it is possible to start a Versus mode game against a team entirely composed of computers. This is caused when two or more people are playing and one of them joins the Infected team and the other is a Survivor, although the Survivor cannot be the host. If the Survivor goes to the menu to change characters, the host can restart the server with the Survivor on the Infected team. This is actually still possible and serves as a great way to practice your Infected tactics such as hiding spots and Hunter wall jumps. If you wait long enough, the doors will open by themselves and be unable to close, possibly due to problems with Survivor teams not opening the door, and then leaving, causing Infected players to be stuck in spawn mode (this has been tested on PC and Xbox 360).
 * If a player is healing someone and the person being healed is constricted by a Smoker and pulled away, sometimes instead of automatically stopping the process, the game will allow the attacked teammate to be healed.
 * If a player heals a Survivor holding any of the shotguns, that Survivor can't start reloading his or her shotgun manually or automatically after he depletes magazine during the healing process.
 * Sometimes if a Witch is behind a door and a player opens it, she will not be startled but instead act as if she has killed a Survivor and run off. Doesn't work if she notices the Survivor approaching and gets up.
 * Sometimes Tanks (no matter if burning or not) may get stuck on closed saferoom doors even when the metal bar has been taken off and no Survivor is blocking him, allowing the Survivors to easily kill him or waiting until he burns.
 * If you start to reload and then pause your game, the reload will still continue. However, when you resume the game, you will have to reload again. This works best on an auto shotgun. If you use all of the shells, pause and then reload the game at the eighth shell, and it will reload the other two. Resuming the game will reload all 10 shells. However, it will still say eight shells until the ninth and 10th are entered into the gun. This glitch is only effective on the PC version.
 * On Xbox 360, you can make expert campaigns easier using the safe room exploitation. First, play through any campaign on easy until you reach the safe room before the finale. After the finale is loaded, do not exit the safe room. Call a vote to return to the lobby. Once back in the lobby, change the difficulty to expert and change the level to the finale. Once you have done this, load the game. You should start in the same safe room before you called the vote to return to the lobby. All your progress for the campaign has been instantly changed so it counts towards expert completion. However, you must complete the finale level on expert, which can still be very difficult. It is recommended to use campaign-specific finale exploits/methods to make the finale easier. Recommendations are listed below in order of increasing difficulty:
 * 1) Death Toll, 2) No Mercy, 3) Dead Air, 4) Blood Harvest <--- This is by far the hardest of all four campaigns to complete
 * Rarely in Campaign mode, if your team loses while you are incapped, you might come back with the screen slanted, as if you were still incapped. This remains until the round ends, even getting incapped will not help; this just makes the slant twice as bad. This bug can be fixed by being knocked back because your screen shakes, thus making your screen normal.
 * If you startle the Witch just as a Smoker constricts you, instead of hitting you, the Witch will get rid of the Smoker's tongue first. It will not work on the Xbox versions.
 * Sometimes deadstopping a Hunter will cause him to get stuck inside a Survivor's body, leaving him very hard to get shot as usually any bullets shot will hit Survivor instead of the Hunter.
 * In the campaign mode for Dead Air during the Finale, it is possible to get on top of the airplane. If a luggage cart is positioned near the left wing of the aircraft, and there are at least three propane tanks, it is possible for a Survivor to pile the three propane tanks under the cart, explode them, flip the cart over near the edge of the wing, and jump atop of the wing. Being on top of the plane gives 100% protection from Tanks, Boomers, and the Horde. Smokers can still pull Survivors off, and Hunters can pounce them. The rear of the plane has no planning and any Survivors that walk on it will fall through the aircraft, so Survivors must stay on the wings on the center of the aircraft. This has been removed for versus play as no luggage carts spawn near enough to the plane for a Survivor to flip on near the wing.
 * On the same map in Survival mode, standing near the damaged fence between the truck located near broken parts of a plane and police tape (on a small gray piece of dirt and rubbish which isn't colliding with Survivors) may cause the AI Director to completely stop spawning most of Infected even if bots are standing in other normally accessible places. The only possible threat are Smokers and Tanks, but they both have a hard time to get to hiding player, usually ending in Tanks dying out of frustration and Smokers walking around the plane and being easily killed by bots.
 * In the Death Toll finale (and in every other custom map with water deep enough to make your Survivor drown) you can easily heal yourself to 100% health. You need to have at least about 30 HP and start to heal when you start to lose health due to drowning damage. If done properly, you will get something above 80 from healing and after getting up you will gain additional health lost from drowning. Then, you can drop down to below 50 HP, eat pills and after getting up temporarily boost yourself up to 150 HP.
 * If you don't need to get full health back, then you can eat pills and make your Survivor drown – your health will be restored as permanent instead of temporary. Interestingly enough, if you get incapacitated twice because of drowning and get revived in black and white mode, as long as you stand up to get back your health, your vision will become normal again as if you healed up and the next incapacitation won't cause death.
 * If you heal either yourself or a teammate while the saferoom door closes with all the Survivors, some of the process will be skipped and healing will be quicker.
 * However, if you do this on an idling player, the Survivor won't be healed, but the medkit will still be used. Applies to both L4D and L4D2.
 * Known only to work with Hunting Rifle, it is possible to melee with your weapon and get a headshot, but this is rare.
 * There is an odd glitch that occurs when Bill is shot by Francis.
 * When the glitch occurs, one can see (as a different Survivor or in third-person view) that Francis' head and mouth move, which is in sync with Bill's words. When shooting Bill from a distance, the Francis player can hear Bill's scolding clearly, as if Francis was speaking with Bill's voice. Francis also displays Bill's unique facial animation. Using one of Francis' voice commands while shooting Bill will cause the friendly fire quotes to play properly because Francis is already playing a Response Rule.
 * An easy way to see this is by selecting Francis, aiming at Bill, then switching into third-person shoulder mode and setting "cam_idealyaw" to 100-150. Another way to check it is to use any of voice commands when Bill is yelling at Francis – it will instantly cause Bill to stop talking.
 * The glitch has to do with the Response Rules for Bill, as the FriendlyFireFrancisNamVet response is present and set to IsBiker which makes the response's rule search for Francis (who is marked as Biker in the global_actors.txt), causing Francis instead of Bill to shout. This glitch occurs in both Left 4 Dead and ported campaigns in Left 4 Dead 2.
 * When someone is playing as Zoey, has low ping and uses one of the shotguns, after loading more than one shell her arms may get stuck in the position of loading shells into the weapon. Can be fixed by changing weapons, being attacked by Special Infected (after being released the shotgun is reequipped) or reloading again. Doesn't occur when using the full reload animation. Also doesn't occur in L4D2 as Survivors there use only full reload animations (excluding pistols).
 * It is (was?) possible for Hunters to jump 'under' certain doors such as the locked alarm-door in BH2 (Video) and some safe room doors. Crouch near the door and pounce at it repeatedly.
 * Very rarely, it is possible for three Tanks to spawn on the roof of the apartments at the beginning of No Mercy.
 * During a Versus match it is possible to revive incapped survivors as the infected. Simply incapacitate them, approach them, and hold X. The camera will pan out and put the special infected in a third person camera and state "Helping up your friend" with the status bar filling up. It is possible to do this as every playable Special Infected. It is also possible to do this in ghost/spawn mode..
 * Sometimes when doing an action such as helping up a Survivor the rescuer may look idle and not show the helping up animation. This usually happens when the use key (to help teammate) was pressed while the target Survivor was in midair.
 * While in a Survival match on the Bridge level of the Blood Harvest campaign it is possible to glitch yourself through a wall. You will be outside of the level, and underneath of it, unable to be harmed. To do this you must find a specific spot. Directly out side of the spawn, there is a red train car with supplies on it, behind that train car is the wall through which you are able to slide through. You must run into the wall, and crouch repeatedly. It also helps if you melee the wall while crouching up and down, and running back and forth. It is possible, but not confirmed, that holding a propane tank, or gas canister will help. Once you slide through the wall, you be able to see unused blank white space off in the distance, and through the walls in which the game actually takes place. Once inside the white space, it is possible to crouch, and walk to where you start the event. Be careful while exploring under the world because it is possible to get yourself stuck, and then teleport out of the white area to the nearest teammate (AI or other player). If however, you are the last survivor, you will be stuck in the ground, and will die from the infected. Smokers, Boomers, and Hunters will tend to avoid the spot, while Tanks will run up to the survivors, attack the ground, and then die. Every now and then a single common infected will glitch through the wall and attack you.
 * It is very easy to create a 5th Survivor on any map in online play. You have to have at least 2nd player not idling and know on how to use console commands. After start of game, you need to go to spectator mode (spectate) and then use command to set yourself as Survivor which is already taken over by other player (jointeam 2 < name of Survivor > ). As a result, it will create an additional Survivor, dead and waiting for rescue in the nearest rescue closet with nothing but a single pistol – and it will be you. Possibly it allows you to create more than one additional Survivor, but it will always be a bot and nobody more can join and play as additional Survivors over the maximum number of slots. After map transition, the number of Survivors will be set back again to four. Interestingly enough, it is possible for game to actually get rid of one of Survivors and instead replace it with copy of other one, allowing to have e.g. 2 Zoeys in game. However, if somebody joins the game, in this case the second Zoey will be replaced with the missing Survivor. Doesn't work in L4D2 as you are not allowed to use any of commands needed to perform this glitch.
 * In Versus mode, playing No Mercy's finale level and dying as the infected sometimes causes the game to crash with no error screen.
 * On the Finale of No Mercy, go in to the Developer Commentary (if you have it) and then go to the minigun. Once there: jump, crouch, melee, and then press X. If done correctly, you will get teleported in/above the spawn room. (Xbox 360/One)
 * In very rare cases, while playing co-op offline on split screen, after killing a Tank another one will spawn, creating infinite horde of Tanks. (Xbox 360/One)
 * On the PC version of the game, it is possible for the Credits map to load incorrectly. The credits will not display but the music will initiate, and the player is free to walk around in the credits room that contains only one textured wall. To do this, select credits from the extra's menu.
 * When playing the Xbox 360 version of the game via backward compatibility (i.e Xbox One), on rare occasions during gameplay, the audio will cut off completely and the only way to fix this is restarting the game.

General

 * When escaping from a finale, if any Survivors are incapacitated near the rescue vehicle, their bodies are not shown. Despite this, you can still hear them calling for help. However, if a Survivor is being pinned by a Special Infected, only the Special Infected can be seen on the screen.
 * If the other team votes on kicking a player, you will be able to see a vote passed and failed window. This is unpredictable, and will show random things in the window (such as "Vote passed! Kicking player - Unnamed, then changes to the actual name).
 * It is possible to save yourself and get a message "YOU saved YOU", if Special Infected attacking you will get burned because of Molotov or Incendiary Ammunition you used earlier.
 * While using a Pipe bomb, it is possible to gain a "protect" and "hit" at the same time. To do this, Commons must be attacking and a Pipe bomb must be thrown within range enough for a "protect". Once the Pipe bomb explodes, you'll receive a message saying "(Player name) protected (player/bot name), but the "hit" message will not appear.
 * An exploit allows you to earn THE REAL DEAL and STILL SOMETHING TO PROVE achievements "easily" (there is a lot of team coordination and timing involved). Each member of the team are assigned one of two roles: sleepers and glitchers. Sleepers will be receiving the credit for Expert/Realism completion, glitchers will do the work but won't get anything. The best scenario is to have two sleepers and two glitchers and then trade roles. Before starting the campaign, make sure the game is set to "private" and have everyone in party chat. Play through any campaign on easy until you reach the saferoom before the finale. Once the finale saferoom loads, do not leave the saferoom. Sleepers quit out of the game and return to the main menu leaving the glitchers and bots in the saferoom. Before leaving the saferoom, one of the glitchers needs to send game invites to all the sleepers. Sleepers need to open the invite, and highlight "accept invite" but do not accept the invite yet. Glitchers can now exit the saferoom and play through the finale on easy. Right before the rescue vehicle arrives (after the second Tank), a glitcher needs to call a vote and change the difficulty to Expert. The moment the vote passes, sleepers need to hit accept invite and enter the game. Once in the game, sleepers need to immediately get to the rescue vehicle. If done correctly, any sleeper who makes it to the rescue vehicle will receive the achievement.
 * The Taannkk!! Mutation has numerous issues, most notably that Tanks can spawn outside of the map, and are unable to attack the Survivors or respawn unless killed by another Tank. This seems to occur most frequently in No Mercy. In addition, it's quite common for Tanks to spawn far behind Survivors, and be unable to catch up to them, however this is most likely because the Tanks would gain a huge advantage if they spawned ahead of the Survivors.
 * A minor HUD glitch can occur if one is using third person view (via developer console). If the player heals with a First Aid Kit in first person view, but then switches to third person while healing and finishes in this state, most of HUD will disappear (only own health will remain). Can be fixed by going back to first person view or switching the map.
 * When playing an original campaign with the original cast, they make one of the L4D2 Survivors' screams when falling to their death.
 * Pressing the Home button or opening the guide will freeze the game until you go back into the game. It may also cause the loading time to extend. [Xbox One]

Infected

 * While you are climbing on a ladder, no Common or Special Infected can go up or down it.
 * Any Special Infected (except Smoker) can melee even if it is stumbled. This is especially annoying in case of Jockey, which instantly hits Survivor if it didn't manage to lunge onto him. Oddly enough, constantly shoving Special Infected is more productive as almost any Special Infected quickly dies and this tactic minimizes chance of being hit.
 * If you shove a Hunter as soon as he gets on another Survivor, he will not stumble. If you kill him or melee him off the Survivor, he will stumble and you will end up with two or even three "You saved VICTIM".
 * If you're being dragged by Smoker and standing on some obstacle which Tank can move (like trash container or car), you will suffer choking damage while still being dragged. Same thing can happen when Smoker hits jumping Survivor, although you will also see choking Survivor getting pulled in mid-air.
 * Sometimes, if you are stuck on an obstacle with a Smoker choking you and Infected nearby are attacking you, you will not suffer the Smoker's choking damage and instead be hit from anyone attacking you.
 * When being dragged by a Smoker and it cannot drag you any further, you may not receive any damage. Only happens in specific locations.
 * Chargers might occasionally ram players into bushes or other obstacles, causing them to get stuck indefinitely until they are killed. May even happen on solid ground.
 * If you are rammed by a Charger into a temporarily unmovable object (e.g. a healing Survivor), the Charger will stall for a second, then run backwards (still carrying you) until a medium distance away from the group of Survivors. It will then pummel you normally.
 * If a Charger does his charge on the Survivors, he will go forward, but later he may charge backwards even though he is facing the wrong way. Even happens if he grabbed a Survivor.
 * When a Charger grabs a Survivor, teammates are able to hit grabbed Survivor with friendly fire. Survivors attacked by all other Special Infected are immune to friendly fire.
 * If you are rammed by a Charger and lose all your health when he finishes his charge, for a split second you will be put in regular incapacitation before being pummeled.
 * When incapacitated by a Charger indirectly, and a couple of strange things can happen. You will be thrown away normally, but you will "bump" up and down while doing so. Or you will get up, but when the animation finishes, you will be instantly incapacitated.
 * If you are being pummeled by a Charger and have a Hunting Rifle zoomed in, you will be able to view through the scope of your rifle in the direction which the camera is facing.
 * When a Tank is pursuing you, you can crouch behind a door and the Tank won't be able to break in. He will instead be stuck swinging his fists without doing any damage.
 * Sometimes, a Tank may punch you to an inaccessible area and then you get downed by his Rock Throw. You cannot be saved and will end up bleeding out.
 * If you throw gas can close to Wandering Witch and shoot it indirectly with Grenade Launcher, the Witch will be set on fire, but won't be startled.

Versus

 * If another player charges past you as the Charger when you are not spawned yet, you will stumble as if you were spawned at the time.
 * Occasionally, items in a metal storage truck can be pushed through the bottom of the truck by a Jockey crouching on the item. Also, just melee-attacking it as any other Infected can cause an item to move and sometimes teleport short distances away.
 * If all four Survivors are incapacitated in the saferoom, the score will calculate twice: once because they are downed, and again because they reached the saferoom. Though the Survivors won't get the 25-point survival bonus, their score is effectively doubled.

Items

 * If you deploy an ammo pack in any place you can revisit (e.g. a saferoom), you can actually get two lots out of it as long as it's not depleted.
 * A rare glitch occurs when a Survivor is wielding a melee weapon an item appears in a fixed position between his/her feet.
 * While switching weapons, it is possible to have your gun completely reloaded, even if switching to a different gun. Only works on the correct weapon types and tiers. For example, if you have one ammo left if your AK-47, and find a M16 Rifle spawn, swapping your AK-47 for the M16 and then swapping it back for your AK-47 results in the gun having the maximum amount of ammo.
 * If you empty the whole clip on any weapon and then swap it for a Sniper/Hunting Rifle and zoom in to the weapon you emptied the clip on and pick it up, it will switch you to your Pistol/Magnum and still be zoomed in.
 * When you are incapacitated, hold the shove button and fire off your pistol, this will cause the pistols not to make any noise whatsoever.
 * If you get hit by a Tank while switching from a melee weapon to your gun, you will be stuck with your melee until hit by a Tank again.
 * If you get a Grenade Launcher and have another Survivor jump above you, you can shoot on their feet with a grenade and they will fly about 50-100 ft (depends on the angle) opposite to where you're facing . This allows you to explore inaccessible areas, and in Survival, can give you an easy gold medal.
 * It is possible to make it with a Grenade too, although the Survivor won't "launch" as high. Getting hit with the grenade won't do any damage to both Survivors.
 * Very_visible_M60.jpg is highlighted sooner than other weapons.
 * If player was carrying an M60 when they were killed, they will be carrying another M60 with a full clip, once they are released from a closet or the next map. Any special ammo will not be kept.
 * If a door closes on an Assault Rifle while it's in mid-air after being dropped by a Survivor, the Assault Rifle will cause the door to shut halfway and standing in the corner where the gun is will cause the Survivor to rotate clockwise until they step away from the door.
 * Car alarms will not go off if shot with Incendiary Ammunition, even if the car is shot at point-blank range.
 * While using a Pipe bomb, it is possible to gain a "protect" and "hit" at the same time. To do this, Commons must be attacking and a Pipe bomb must be thrown within range enough for a "protect". Once the Pipe bomb explodes, you'll receive a message saying "(Player name) protected (player/bot name), but the "hit" message will not appear.
 * Chainsaw_aerial-blood_glitch.jpg visual glitch on the Chainsaw can be found if the player uses the Chainsaw for a long time against the Infected or on the Survivors, then immediately points upward on the air (without even releasing the button); this causes the stream of blood from the saw to remain whilst the button is held. It will be displayed like the player is hitting an enemy in mid-air. Blood even drops down the floor during this process. However, this stops if the Chainsaw is out of gas or if the player has released the button.
 * When interacting with weapons while holding a chainsaw, it the captions will show the [chainsaw starts] text, even though you're not switching to your chainsaw.
 * Awkward_arm_position.jpg melee weapons are glitched when playing in third person – there are no animation for one of swings (in case of i.e. Guitar). Also, when using buttons or opening doors (usually done with left hand), a Survivor will use right hand, but in position of left hand, resulting in really awkward appearance with Katana, Baseball Bat, Cricket Bat and Golf Club (doesn't affect Axe and Guitar as they use custom animations). This was somehow fixed as Survivors now just use left arm to push buttons, but it makes holding weapon flicker in an odd way.
 * While on a local server, switching to third person mode can cause your melee weapon to become invisible. The weapon can still be used properly, although you do suffer from character model issues, i.e. your arm goes the wrong direction and inside your body when you pick up a weapon.

Levels

 * In the Hotel, if a Survivor dies in an elevator, the elevator will descend but the Survivor will not. If the elevator starts moving and the Survivor is revived while ascending, the Survivor may respawn on top of the elevator. However, the game will quickly take notice, and will teleport you back to your team.
 * In the Atrium, before the elevator, if you go to the plant near the elevator and jump to the edge, your character will make their falling to death sound and die.
 * In the Atrium, by starting the elevator when someone is incapped outside of the elevator, it is possible to begin the finale by pressing the use key on the Information stand near the car. Though the finale has been started, it will behave strangely. Sometimes when you get all the cans into the car, you will not be able to complete the level; other times, it will behave as normal.
 * During the Atrium, if once the car is full, the Survivors fail to escape and at least one Survivor is incapped on the podium with the car, the game will show the beginning of the escape scene while playing the death music; the scene will stop once it reaches the slow-motion part. After a short while, the game will reload the saferoom, except the game will still be in slow motion.
 * In the Underground, the Survivors go down a long set of stairs and then drop into the sewers. Around the back of where they fell, there's a broken set of stairs. If you attempt to jump up the stairs, the Survivors will verbalize as if they were falling down a steep hill.
 * During the Highway and The Park, the sound of rain may play, despite neither of the chapters having rain. [Xbox 360]
 * In the Highway, after you leave the motel, when you slide down the hill, land on the slope to the left. If you jump back onto the slope you can repeatedly say one of the quotes on your character when they go down the slope.
 * In the Highway, after leaving the motel and sliding down the hill, go around to the other side of the big rock to the right. Next, walk towards the rock and by continuously pressing LB on the Xbox 360 controller, in certain specific spots you will clip inside the rock. Another place this can be done is right after you slide down the hill there is a rock wall to the left. This one is much harder to do, but on a specific spot, you can clip through the wall and get inside, going out of bounds and under the map. Sometimes you will get stuck while clipping through the wall, and eventually through time this will teleport you to the nearest Survivor. In Survival Mode on Motel, if you start the round while you are inside the wall, you will get randomly spitted. However, if you stay near the wall and don't move at all, the random spitter will not get you. This is one method of getting infinite time on Motel.
 * It is possible, through co-operation, to survive nigh-indefinitely in the Motel Survival. First, get three players rocketed over the fence to the secret zone with the grenade launcher, taking healing into your own hands. Then, go to the staircase near the motel lobby. Hop on the railing, crouch and walk up the railing to the top, then walk around a little until you are unable to move. In a few seconds, you will teleport to your teammates. Heal or revive people if you need to do so, and head to the end of the map. Do not close the saferoom door if all players are inside, or all players will be kicked, and the game will say that DLC was selected. Have one player go inside, shut the door and open it so that it faces outwards, then shoot the alarm car to start the timer. If all of the players hide in the back corner, on the door's side but away from it, some common infected will occasionally get in, Tanks will attack the door and then die for seemingly no reason and no other Special Infected will reach you.
 * As a extension to the above glitch, there is a shopping cart near the safehouse door. Until the round is started, it will be impossible to move it unless you have a gascan or a propane tank. After it starts, shoving the cart until the wheels face towards the sky, right next to the thin side of the door (a difficult task) will allow players to jump onto the cart, then the door, then the safehouse. There, they can either jump down into an small, enclosed area leading to an invisible wall in front of Whispering Oaks, or run across the green barrier to the larger enclosed area, although this is accessible to Tanks and Common Infected. You can also get on top of the buses and onto the enclosed area beside them by shoving the shopping cart into the corner where the two buses meet and jumping using the shopping cart to jump onto the bus's mirror and onto the buses or over to the enclosed area.
 * During the Concert finale, it is possible that Director may not spawn any Tanks or spawn only one. You can slightly increase chance for this bug to occur if you will crouch on the top of higher scaffolding (the one of left side of stage).
 * Becoming increasingly frequent in the Concert, the final horde and a Tank will spawn as soon as you start the tape, and the rescue helicopter will instantly spawn at one of the two stationary points for pick-up. This has also been reported to happen during the Plantation finale, where the gate will be broken down as soon as you call for rescue from Virgil. This can also occur in Town Escape finale where after you signal Virgil with the Burger Tank sign the boat will almost immediately pull up to your rescue. It also happens during the the Atrium where the final horde and endless Tanks show up once you exit the elevator. Even if you gather all gas cans and gather the Survivors by the car, you can't complete the finale, and this bug will recur if all the Survivors are killed, forcing you to return to the lobby and restart the campaign, and rarely, in No Mercy where after you call the pilot, the Skin on Our Teeth will cue then the helicopter instantly spawns.
 * In the Concert, any incapped Survivor who didn't enter the finale area and aren't near or in the saferoom when someone else starts the finale will be removed from the map (into the main menu with a message "An error occurred with your connection"). This also applies to Special Infected when they're inside when the finale starts. [PC unconfirmed]
 * During the Plantation, when the Survivors escape on Virgil's boat, there is an invisible corner where anything that goes there will be instantly killed. Common Infected point out this location, and when they reach that corner, they instantly die and float in the water.
 * In the Milltown, the bots will grab the Tier 2 weapons in the saferoom of Return To Town (right after the small trailer). They walk up to the wall and grab the weapon right through the wall, and can also grab any other item they wish. Human players cannot achieve this, even if they use the "break" option to release the control to the bots.
 * In the Sugar Mill, you may be spawn as a Tank under the cane field.
 * In the Bus Depot Survival, it is possible to get on top of one of the buildings to avoid theInfected. When you start the event and turn around to go to the fence adjacent to the starting point, there is a corner with trash bags and three pipes on the wall. Continuously jump in the corner until you are on the object. Shimmy over and jump onto one of the pipes, then the next, the next, and then to the roof.
 * In the Bridge Survival, you can make the game freeze (requires a friend). Begin by taking a grenade launcher and crouching on the top-right corner of the helicopter platform. You can grenade jump your friend onto the bridge; he will run at you and jump on top of you while you shoot the grenade launcher, and he will continue running in mid-air. (This is extremely difficult, and if you're unlucky, both of you will die, him pushing you off and jumping into the water) When he is on the bridge, you can crouch under the trailer and use the teleport spot to join him. Once on the bridge, you can run all the way to the end, where the bridge's gate isn't lowered. When you walk right up to it, the game will freeze, making you have to restart.
 * In the Bridge, there is a way to get beyond the level boundaries (video). After you reach the Tank (kill him, or else he will be a bother to you), then, when you get to the part after the Tank where you have to climb on top of the bus to get to the higher level of the bridge, there should be another blue bus next to that one you climbed on, jump on that, then jump to the suspenders along the side, and walk up, you'll be on top of the bridge (the very top). Now you can just keep moving forward, and going outside the map, once you see those square buildings outside the map, there is one that you can reach from the top of the bridge (don't jump off, just fall off the edge, it does a lot less fall damage to you), now fall off the top of the building and explore!
 * In the Port Versus or Scavenge, being vomited on by a Boomer does not always spawn a horde, rendering the Boomer useless (typically, being "biled on" spawns additional Infected at the nearest spawn site).
 * In the Port Survival, you can finish the campaign, even though you shouldn't be able to. Make your way to the ladder part of the bridge (prop-building, low gravity or grenade launching), make sure everyone is on this ledge, then hit the switch. The finale will resume like in the real campaign, the switch will turn and the bridge will raise, once the bridge stops, get down carefully, and restart the generator. Four Tanks will spawn, and an Infected ladder will be created for them to climb on the bridge; this can be disastrous if you are not prepared, as all the Tanks already here and the new ones will just rush up.
 * This will also generate a new glitch on "Survival Campaign" win (by restarting the generator), if Bill is the one who restart the generator, everyone will be awarded KILL BILL achievement. It will also create a glitchy endgame board that can't be skipped, and will show empty stats, except for the time that will be the Survival timer at the time the generator is restarted.

Fixed
For a comprehensive list of things that have been fixed or added to the game, see Update info. Some bugs need confirmation as to whether or not they are still present. Discuss on the talk page.
 * You are able to fire the entire magazine of an Assault Rifle or Submachine Gun in a second. [fixed 9/22]
 * A glitch involving a gas can can give you infinite Molotovs. Can be very useful in a Crescendo Event. [fixed 9/22]
 * You're able to claw a Survivor while still selecting a spawn point, and they're completely helpless. [fixed 9/22]
 * If the Survivors see ammo piles, they may refer to it as weapons. Nick is the only new Survivor capable of proper spelling. [fixed on 1/18]
 * While using the Hospital's elevator, if you jumped enough or throw an oxygen tank at anyone, you could fall through the floor to your death. This has been prevented by not letting you jump at all.
 * If a Survivor was revived once the elevator had been activated, they were left behind. The elevator would rise but they would not. They are unable to leave the elevator shaft, and have been easy prey to the Infected.
 * A Common Infected can become invincible, which means it can't be killed but will still try to kill you. To get rid of the glitched Infected, trap it inside a place and close the door.
 * If you throw a propane tank at a Witch and shoot it, the Witch will disappear, but you can still hear her sobbing.
 * Cr0wning a witch can occasionally render her immortal. [fixed 12/1]
 * Switching weapons while using your melee attack would allow you to attack faster than normal.
 * If you tossed either a Pipe bomb or a Molotov, then immediately picked up another, you could continuously spawn new grenades.
 * After being in the close vicinity of an explosion, rapidly changing weapons would cause the player to reset the stumble animation and move him backwards, or "air walk", until the player collides with a wall or if weapon cycling ceases. This allows entry to normally unreachable areas because this cycle maintains your height, suspending you in the air if done off a ledge.
 * There was a way to have more than four Survivors. The second you open the door to the rescue closet, start to revive the dead Survivor with a defibrillator. But now when you save the Survivor in the closet, their corpse disappears.
 * Melee hitting the Minigun repeatedly and jumping onto the it would launch the player into the air. You can skip decent-sized chunks of maps, as well as get to out-of-reach places.
 * In The Streets, it was possible to skip the Crescendo Event by pouring a gas can into Whitaker's door instead of the cola.
 * It is possible to get past the downed airplane in Swamp Fever without ever triggering the alarm. If you walk the length of the plane to the back rows of seats there is a large gash on the right side. On the far side of the gash, crouch and walk towards the hull you will be partially outside the plane. If you stay crouched and jump, you will reach the roof of the plane and from there able to jump down without the crescendo event starting.
 * During The Passing finale, Survivors may yell out either something to do with the bridge or Jimmy Gibbs Jr.'s car, regardless of the rescue vehicle. Although the Survivors can yell out the correct rescue vehicle, most of the time, they do not.
 * During The Passing Survival, there was a way to refill the M60's ammo. If you picked up a weapon close to M60 spawn point, it would go back to its spawn position. Upon being picked again, the M60 would be refilled with 150 bullets, regardless of how much you used. [fixed on 6/9]
 * If Nick would die, Coach and Ellis fall into mourning, unable to speak anything until Nick is back to the realm of the living.
 * You could defibrillate a Survivor regardless of their Z axis position (their height). You could revive a dead Survivor 100ft above you, but you have to be right next to them in other dimensions.
 * To play on a hidden Survival map, get out of bounds on a selectable map, go to the saferoom and proceed onto the next chapter of the campaign, and then restart the round. You can try this on the secret roller coaster map.