Tactics

"Stick together!"

- Francis

"Don’t nobody wander off!"

- Ellis

Assuming a certain level of basic skill and familiarity with tactical shooters, these Tactics should help you and your fellow Survivors get through Left 4 Dead... alive! As a start, make sure you know all of the Controls.

Above all else, no matter which team you are on, the Survivors or the Infected, in the end you will be depending on the people around you to survive, as well as to have an overall good experience. This game requires cooperation on all sides, so be kind, treat others nicely, don't go overboard with the trash talk, do not belittle your teammates and be patient with the less experienced players. With luck, they will return the favor.

Note: These tactics are written specifically for the Survivor players, though an Infected player can read through and figure out counters to these tactics written below.

General Strategies
In-game, Survivors usually play through the campaigns following certain main strategies; note, however, that these strategies are suggestions, not obligations, particularly in chaotic or critical situations. Survivors should still keep in mind what they are doing and get back to formation when such situations end.

These are the main strategies that Survivors use in-game:

Sweep and Clean
Survivors stay together, travel through the map while taking out any Infected they meet, aside from Witches that can be avoided. When running past a room or space on the side of the path, Survivors either ignore it and run past, or send in one or two Survivors to search for supplies and kill the Infected inside while the others guard the entrance.

This strategy is used most commonly in Campaign Mode when traveling through the map on easier difficulties, as the Horde and Special Infected are not so dense and are less threatening.

When using this strategy, it is best for Survivors to have a balanced weapon formation. Pistols, Hunting Rifles and Sniper Rifles are effective when clearing the field and saving ammunition while other weapons can be used to deal with the Special Infected and Hordes.

Rushing
Survivors stay together, travel through the map and head toward their target quickly, ignoring Common Infected that aren't hindering movement. However, the team usually leaves behind incapacitated players, and there is a risk of dying faster if rushing with bots, who struggle to catch up with the player.

This strategy is used most commonly in Campaign Mode when traveling through the map on harder difficulties. It's also common in Versus, Scavenge, during gauntlet Crescendo Events, heading toward the rescue vehicle in the finale, or when Survivors need to reach a resupply point or a more secure location. The player should have a fairly good amount of knowledge about gimmicks and shortcuts of the level, which can help them reach the safe room faster.

In both Left 4 Dead and Left 4 Dead 2, players should always carry shotguns, as it will clear out any Infected that may be close to the player. While there's the risk of stray bullets accidentally hitting Witches, assault and scoped rifles fare poorly in close range.

In Left 4 Dead, while melee weapons do not exist, players are able to infinitely shove nearby enemies. Pistols shouldn't be used in any circumstances.

In Left 4 Dead 2, a melee weapon can conserve shotgun ammo for upcoming Crescendos. Bile bombs are also valuable for rushing. When everyone leaves the safe room, a player with the bile bomb will throw it into the safe room and close the door. This will generate a Horde, who will attempt to break the safe room door but be unable to due to its programming. The Director cannot spawn Common Infected if they are performing an action, meaning that there will be little Common Infected on the route, with the only threat coming from Special Infected. As there are more Special Infected, players should spare Boomers and Spitters, as they are the least dangerous and will take up a slot that would be taken by a more dangerous Special Infected such as a Smoker.

One of the main disadvantages of rushing is that the lead player(s) may trigger a Tank encounter, causing the lagging players to be forced to deal with him. In Left 4 Dead, players will have to dodge him or gun him down if they're near a Crescendo Event. In Left 4 Dead 2, dodging him is easier due to the presence of adrenaline shots. Players will still have to gun him down or throw a bile bomb if he's near a crescendo area, however.

Hole Up
During a Horde, Crescendo Events, or in 1st and 3rd finale waves, Survivors do not typically attempt to advance, but instead "hole up" in a relatively defensible location to face the incoming Horde. Survivors stop moving forward and stay put until the Horde attack is over or they are low on supplies, in which case the Survivors switch to the rushing tactic to head toward the supply spot.

The key to the success of this strategy is to limit the directions from which the Infected can reach the Survivors, permitting Survivors to focus fire on choke-points, increasing accuracy and taking advantage of piercing damage.

Suitable locations for this strategy include small rooms with few doors and windows, as well as elevated positions with few approaches and good sight-lines.

When using this strategy, shotguns, automatic weapons, and melee weapons are highly advised, while Hunting Rifles and Sniper Rifles may also be useful if other Survivors can defend the user very well.

For more information, check the "Fighting the Horde" section.

Surrounding
When facing a startled Witch or a Tank, Survivors are on the defensive but cannot stay in one place. Instead, the Survivor being targeted keeps walking backwards, facing the incoming Infected to keep attacking them, while other Survivors strafe left or right to help with surrounding the target. If the Witch incapacitates her target, the rest of the Survivors move up close and kill her while helping the victim back up. If the Tank incapacitates his target, another Survivor draws his attention while others revive the victim.

Opening space is very important for this strategy. It not only helps the Survivors surround the target while keeping their distance, but it also allows them to spread out to avoid blocking one another's line of fire. Therefore, Survivors will usually backtrack to find an opening space when using this tactic.

When using this strategy, it is advised to use shotguns if the Survivors are willing to be targeted and want to fight in close range, while those who want to provide firepower support should choose automatic weapons. It may be difficult to make the target follow the Survivors' plan. Hunting Rifles and Sniper Rifles are not advised due to their low firing rate, pinpoint nature and low accuracy while moving.

Fighting the Horde
Common Infected run fast, come in large numbers, and are often backed up by the Special Infected. This section describes tactics you can use regardless of what your teammates are doing.

Readiness is All
Before the Crescendo Event, Gauntlet Crescendo Event, finales and unavoidable panic events, make sure you and your teammates are ready, and if possible or necessary, make a plan before starting. Especially on higher difficulties, unprepared teams are much more likely to be devastated by the Hordes of Infected.

Doors and Corners
Always close doors when you find them. You can then safely kill Infected through the door. If the hole in the door is big enough, go ahead and use melee through the door. This will knock the Infected back, saving the door from immediate destruction, while keeping you nice and safe. However, remember that this can work both ways, as good Smoker players will grab Survivors through the hole in the door, and Spitters can spit through the hole in the door while the rest of the group is looking in the opposite direction, thinking that it's safe to be behind a door. Also by leaving the door, it serves as a countermeasure against Smokers, which usually spawn behind the team.

Closing doors behind you is also useful while you are moving through a level. The AI Director is notorious for sending Infected from an area you've passed (especially Smokers) and these surprise Infected can slow, injure and separate your team. Shutting doors that you just came through can slow down those sneaky Infected, and might mean the difference between incapacitation, death, and survival. It is especially useful to shut doors in the finale of a Campaign which can make defending them a great deal easier.

However, a Tank or a Witch can destroy the door with a single hit. It is advised to open the doors before fighting them, as this not only saves the door so they can be closed after the fight is over, but it also prevents Survivors from getting stuck, or having to turn around to open them during the fight.

When a room gets thick with Infected, the best cover in this game can be found in a corner or a wall to your back. You can then melee to knock back Infected and shoot when you have breathing room.

Contrary to popular belief, fire extinguishers do not damage either the Survivors or the Infected. They also do not start panic events. Therefore, they should not be factored in when you are deciding where to fight a Horde from. However, fire extinguishers have a similar effect to melee shoving, so setting them off by shooting through a damaged door to push back the Horde can be quite effective, especially when the Infected are in a bottleneck.

Although closed doors are an advantage, keeping doors open can also help the Survivors. The Survivors can then proceed to fight the Horde without running the risk that the door will be destroyed by the Infected. That way, the door can simply be closed, stalling the Infected and giving you time to heal or even resupply if possible.

However, many human-controlled Infected in Versus tend to go through the level ahead of the Survivors, destroying all of the doors. This makes it easier for the Horde to rush in and attack the team of Survivors, making defense more difficult. However, to use this tactic, that player must spend valuable time attacking the doors, during which there will only be three Special Infected attacking the Survivors.

Choke-points
A group of Survivors can survive the incoming Infected Horde if they use a narrow opening to draw the Horde to them. This creates a slower flow of Infected, and allows the Survivors to concentrate firepower all in one direction, making their defense more successful. Examples of effective choke-points are:


 * A narrow hallway.
 * A secure room with only one entrance.
 * A slim rooftop with only one pathway to the Survivors.

Effective choke-point tactics include two rows of Survivors near the choke-point entrance, where two Survivors are crouching up front — usually with shotguns — while the other two Survivors stand up in behind and shoot over the front Survivor's heads. Crouching Survivors can either shoot, shove or use melee weapons and can cover each other while their partner reloads.

Choke-points can be a problem when Survivors forget that a room isn't secure from all locations — this leads to a surprise attack from Infected breaking in from another point (like through a wall or a ceiling) and overwhelming the Survivors.

Choke-points are harder to find in outdoor environments, but you can always use an entrance of a building while inside to fight Infected while they try take on your group.

Other issues include Special Infected taking advantage of the tactical situation:
 * Fortunately, Boomers and Hunters can be quickly dealt with.
 * Chargers and Spitters force Survivors to move out in the open or all get bowled down or covered in progressively more damaging acid;
 * Smokers require Survivors to be aware of their tactics, and they must prevent their teammates from being pulled away too far, or the choke-point tactics fall apart rapidly;
 * Choke-points can work against Survivors when dealing with Tanks as the Survivors are boxed in and can't use their superior speed to their advantage.

High Ground
High ground has been recognized as incredibly important for defensive tactics in real-life military strategy. Similarly, the utilization of elevated positions is an important strategy that should be remembered in-game in defensive situations.

Higher positions give the advantage of time; the Infected take longer to reach the Survivors because they are forced to climb up to them. During this time, they are either nearly still (if they are climbing either a short or medium distance) or moving in a straight line (if they are climbing to a significantly higher position). Both of these forms of movement are much easier to track than the normal zig-zagging pattern that Infected move in while running towards players on level ground.

Additionally, high ground gives the Survivors an unobstructed view of distant areas. This gives them advanced warning about incoming Special Infected, who can often be dealt with before they become a threat. The delay imposed upon Common Infected while they climb makes the task of keeping them at bay much simpler, often requiring only two or three of the Survivors' attention. This leaves one or two Survivors who can focus on killing bigger threats before they reach the Survivors.

A group of Survivors all defending a high ground point using both melee and firepower can really slow down the Infected's ability to disrupt a staged defense. Working together is key in high-ground defensive positions. During finales, you should find the high ground and defend it until the rescue vehicle arrives.

When dealing with Common Infected on high ground, keep in mind that it is entirely possible to knock them off of your high platform to give yourself breathing room. It will take a much more significant amount of time for them to reach you again than if you were simply knocking them back on level ground. If you keep shoving Infected off of your defensive position while you reload, you will probably remain unharmed, even if you aren't receiving support from teammates. Once reloaded, you can resume killing the Infected that you left alive during your reload.

Sadly, being on top of a car, subway cabin or other small object is of negligible value as defense in this game due to the climbing abilities of the Infected. Because the Infected can climb up from any part of a small elevated surface (unlike higher cover, where Infected can only climb on certain parts of the structure), you will likely be completely overwhelmed by a crowd of Infected surrounding you.

Another disadvantage of high ground is the threat of fall damage. Tank punches, Smoker and Jockey drags, and Charger pushes can knock Survivors off if performed properly, either dealing high damage or killing the Survivor instantly.

Special Infected First
During a Horde, Special Infected are still more dangerous than Common Infected: Survivors should try to seek out Special Infected during a Horde and take them down first, especially when they are about to attack or have already pinned a victim. If the attack from Common Infected hinders your aim, shove them back, use a Pipe Bomb or Bile Bomb to lure them away, or use an Adrenaline Shot to disable the stunning effect. Scoped rifles are best at doing this task, although Submachine Guns and Assault Rifles can do this as well. However, if the Infected are completely overwhelming the Survivors, the use of shotguns or automatic weapons to cut a hole in the Common Infected to the Special Infected target may be more effective.
 * Hunters, Smokers, Chargers, and Jockeys can seize one Survivor, which not only make the Survivors short one gun, but also make the victim a sitting duck to the Common Infected around;
 * Boomers can extend the panic;
 * Spitters, Tanks, and startled Witches can cause chaos and take chance to do more damage during a Horde.

Protecting Teammates
As long as there are other Survivors, Common Infected may choose to attack them instead of you. Depending on their weapon, status, and skill, the teammate may be capable of holding on their own without needed attention if they are in good condition, but also may be prone to attack, such as being pinned, incapacitated, or covered in Boomer Bile.

The skill of aiming accurately is needed to support your teammates as much as possible while minimizing friendly fire damage. An automatic weapon or a scoped rifle can easily mow down Common Infected surrounding a fellow Survivor without friendly fire damage if aimed well. Weapons with large spread or splash damage, such as shotguns or explosives, are poor choices, and can easily cause more chaos as the Survivor being helped tries to react to the unexpected attack effectively. Asking your teammates to crouch allows you to shoot above them. Shooting through objects is also an option, as bullets piercing through anything will not deal friendly fire damage.

Throwables also work if used well. Pipe Bombs and Bile Bombs can easily lure the entire Horde away. A few notes:
 * Pipe Bombs are the best throwable of choice here, as they WILL drive away Infected from your team and it'll kill all the Common Infected in range with its inevitable explosion. Note that a Pipe Bomb will not go off in your hand. It'll only start beeping when it is thrown.
 * Bile Bombs will drive the Infected away from your teammate, but you'll have to take them out yourself. If the Survivor you're trying to defend is covered in Boomer Bile, the Bile Bomb will do nothing to the Infected when thrown, as the Common Infected prioritize Survivors covered in bile over a random spot of bile. You cannot cover a Survivor in Bile with a Bile Bomb — only Boomers have that ability.
 * Molotovs can block and burn down an entire Horde, but it will cause friendly fire damage if a fellow Survivor is caught in the spread of the fire along with the Infected.

Melee weapons are another choice, while its large sweeping area means Survivors will likely to accidentally hit their teammates a few times, its friendly fire damage is minimal, and its large sweeping area means the Horde will be cut down very quickly. Friendly fire damage taken will be far less that the potential damage the Horde can dealt.

Alternatively, a bottle of Pain Pills or an Adrenaline Shot can be given to help teammates deal with Common Infected more efficiently if in bad condition.

Interestingly, on lower difficulties, due to low friendly fire damage, weapons with large spread or splash damage can actually help clearing the Common Infected easier, while the friendly fire damage is smaller compared to the damage from the Horde. Even a Molotov to the feet can give great aid if the Survivor is still standing and has high health. It is advised to communicate with the others whether they need help or not, and what you are going to do so they can do their best to reduce friendly fire damage taken.

Deep Water (Left 4 Dead 2 only)
In Left 4 Dead 2, you will encounter waterlogged areas in three of the six campaigns (one of which is DLC, and not including custom made campaigns). Such areas will slow you down considerably, making it hard to navigate through the Hordes of Infected. It will also make dodging most Special Infected harder. However, you can improve your chances of success by crouching through these areas. You will still move at the same speed, but your accuracy will improve.

Overall, avoid watery areas, only crossing through them if necessary (such as The Underground of "The Passing".

Survivors
A Charger must be dealt with carefully, no matter the difficulty. Even on Easy difficulty, the Charger can deal a lot of damage.
 * If a Charger spawns, try to avoid narrow choke-points whenever possible. A well-timed charge by a Charger can knock the whole team down for 15 damage, which allows the Charger to deal more damage on whoever he has pinned.
 * When possible, try to force the Charger to charge, so that he wastes it and stumbles, allowing the team to take him down before he can start meleeing the team.
 * Never attempt to kill the Charger with melee weapons after it fails a charge and stumbles, as it can still melee and result in unnecessary damage to the player.
 * Be aware that not every Charger, be it AI or player-controlled, will charge as soon as possible. They may choose to use their damaging melee attack instead.
 * Don't back up if this happens, as AI-controlled Chargers may instantly charge if you try to back away.
 * Be aware of your surroundings. If a Charger hits a tight-knit group in a high elevation area, this can result in some of the team getting killed by freefalling.

The Infected
As a Charger, your job is to primarily charge towards the Survivors and separating the pinned ones from the rest. Any kills or incapacitation made after bowling through them is usually an added bonus.
 * Lie and wait for the Survivors if you're planning to perform a surprise charge. Assistance with a fellow Special Infected increases the likelihood of a successful charge.
 * Charging too early or too late will cause unnecessary death, thus you will mostly likely not deal any damage at all.
 * Look for areas such as a high elevation or deep water, successfully charging the Survivors in these areas can lead to instant kill. See this section for ambush spots list.
 * Like most of the Special Infected, you can interrupt the Survivors who are performing certain tasks such as activating a Generator to impede their progress.

The Survivors
The Spitter is also a dangerous Infected, especially in tight areas.
 * A Spitter does not have a lot of health, so a few shots from any weapon can kill her instantly.
 * Using a Hunting Rifle or a Sniper Rifle should take care of her easily at long range.
 * If a Spitter spits, your character will warn the others of this. The Spitter will always spit at whoever she spots first when she "attacks", so this can be easily avoided as the spit takes 2 seconds before dealing damage.
 * If you are in the way of the spit, you will be momentarily frozen for a second. Immediately move out as fast as possible.
 * If you are caught in the spit, get away from it as soon as possible. This can be problematic if a Horde is surrounding you, as you will take heavy amounts of damage the longer you are in her spit.
 * When the Spitter dies, she will leave a small pool of acid around her corpse. Wait for the acid to disappear before moving further down.
 * Never try to go around a Spitter's acid, as appearances are deceiving and you will take unnecessary damage trying to go around it in a narrow area. Jumping does not work either.
 * Prioritize killing the Spitter during Scavenge Mode due to her notorious ability to destroy gas cans.

The Infected
As a Spitter, spit over areas where the Survivors are supposed to go or gain advantage, especially in narrow areas such as hallways. With the Survivors unable to progress temporarily or will force to go through the hazard and take unnecessary damage due to your acid spit, this will give your Infected teammates an opportunity. Spitting on a Survivor being pinned by a Special Infected makes it quicker to incapacitate or kill them outright.

As mentioned above, the Spitter is renown to be extremely formidable in Scavenge Mode due to her spit's ability to destroy gas cans. This gives her advantage to Survivors who are accumulating gas cans and dropping them on a certain spot. Spit at the survivors trying to pour gas cans on a generator!

The Survivors
Useful Precautions:
 * Listen for the heavy breathing, gagging, and burping sounds.
 * If captions are on, make sure you know what they mean. When the Boomer "rages", they have spotted you. When the Boomer "falls", they have fallen from a higher area. When the Boomer give a "warning", they are in puking range of you.
 * If you hear one, keep an eye out for defensive positions. That way you'll be ready if the Boomer blinds you.
 * Avoid being too bunched up with the other Survivors. There's no sense in all four of you getting puked on at once.
 * On Expert, Boomers will often claw Survivors they have vomited on, dealing even more damage.
 * On Expert, finding and killing the Boomer before they can vomit or explode is incredibly crucial as the Boomer bile attracts the Horde, which on Expert difficulty, is extremely dangerous.
 * Be cognizant of blind corners, overhangs, and obscured (i.e. wooded) areas where the Boomer may be lurking to get the drop on you. Try to give these areas a wide berth whenever possible. If you hear a Boomer but can't see them, it might be a good idea to fire a couple of "blind" shots into any unseen areas in the chance of hitting the low-hitpoint Boomer.
 * Boomers can kill themselves by falling off a great height. This explosion can slime nearby Survivors if it hits them, so be careful of this. Fortunately, AI Boomers do not utilize this tactic often.

When the Boomer is sighted:
 * If the Boomer is too close, it's a good idea to melee-shove them, which will push them back to some degree, then back away to a safe distance before shooting or you'll get covered in bile, even though you weren't vomited on.
 * Hiding behind something or running away when they're vomiting makes it harmless for some time and may even force it to rush at you clawing.
 * Only if the Boomer is sufficiently far away from both yourself and all other Survivors should you shoot them.
 * In Versus, before you shoot a Boomer, see if it's just staring at you, or if there are crying sounds coming from the Boomer's direction. It's possible that the Boomer is concealing a Witch, so hold your fire.

After being vomited on:
 * Know that a massive horde will immediately descend upon you and any others who have been slimed.
 * Despite their vision and the glowing outlines being disabled when vomited, Survivor bots are still capable of accuracy or tracking down their teammates.
 * Hold your fire! Since you can't see, friendly fire is the most likely result. Shove instead, until you're sure that you won't harm your teammates.
 * Immediately find the nearest defensible corner and keep your crosshairs aimed at any open doorways, or other locations Infected come from.
 * This is not a good idea to kill the Boomer once you are blinded unless you can shove him off at safe distance or are away from your team. The explosion will make you stumble and will likely cover any missed teammates in puke as well as resetting the blindness of every teammate. However, if you are away from your team, stumbling a bit before the majority of the horde descends on you isn't as bad as being clawed multiple times by the Boomer.

Helping a slimed Survivor:
 * Stay close to the stricken Survivor.
 * Help shove the horde back or shoot if the blinded Survivor stays safely crouched.
 * Help the stricken player to safely get to a corner to protect him from the horde.
 * Throw a pipe bomb to distract the horde (it is bad to throw a bile bomb as the horde will ignore it, thus leading to the useless waste of a precious item).
 * Stay out of the biled Survivor's way: they may mistake you for a zombie and shoot you, which could be disastrous on hard difficulties. If they are swinging their melee wildly, it is very easy for them to accidentally hit you unless you're a bit away.

The Infected
As a Boomer, your job is to slow the Survivors down by attracting the horde. The Director will spawn one horde for each Survivor vomited on for a maximum of four. As a Boomer, you will need to hide and ambush Survivors since Boomers have the lowest amount of health, and emits a lot of loud burping and gurgling noises. The Boomer acts more like a support class, as they don't dish out much damage on their own. Due to this restriction, they excel when placed at the start of any coordinated attack. Their main attack attracts the horde, causing Survivor teams to panic, which creates ideal opportunities for the other Special Infected to move in and deal serious damage, and also blinds survivors, giving special infected a chance to carry survivors away from teammates unnoticed. Remember that you have very low health and will explode in only a few shots. If you try to rush at the Survivors in the open, they will simply kill you before you get within vomiting range.

Another weapon of the Boomer is that it explodes when it dies and covers any nearby Survivors with bile, which has the same effects as vomit and also causing them to reel back. This explosion is a good way to cover any Survivors you missed because inexperienced players have a tendency to shoot on sight instead of using a melee attack to knock it back to a safe distance. You can vomit on unsuspecting Survivors below with impunity if attacking from rooftops. Then jump down to let them shoot you in blind panic, if your health is low enough or you are high enough up you can instantly explode as you land covering any nearby Survivors! Exploding on a person who is already covered in bile does not spawn another horde, so you should either retreat until you're ready to vomit again or to get as close to the other Survivors as you can in the hopes that they'll cause you to explode bile onto other Survivors.

Take advantage of blind corners, overhangs, and obscured areas (such as woods) when choosing where to strike the Survivors. Such areas increase your chance of success, as they allow you to get closer to the Survivors before they have a chance to kill you.

Experienced Boomer players can use the knock-back effect of the explosion very effectively by knocking Survivors off high ledges doing large amounts of fall damage, if high enough, cause instant deaths or incapacitation, or causing them to cling to the ledge and need to be pulled up. As a Boomer, claw at Survivors if it doesn't look like you can escape or if you want to explode and knock the survivors back.

If you explode near a car with an alarm, this will set it off. So if you can, quickly go vomit on the Survivors, retreat near a car alarm, and allow yourself to explode setting off the alarm and spawning another horde.

In some situations, it may be possible to kill a Survivor that has become separated. This is achieved by sliming them, then clawing them. The boomer is able to knock Survivors to the ground, leaving them vulnerable to attack. This technique leaves the victim no room to breathe and they will be quickly incapacitated, and the dense horde will hinder the attempts of their teammates to revive them. The hoard also does 10 damage per hit to incapacitated players (not changed very much based on difficulty), so the infected only need to hit the survivor about 26-28 times (accounting for normal health loss) before they kill the survivor.

Fire may also be an effective weapon for you. A Boomer that is lit on fire effectively becomes a "ticking timebomb", and once its health is depleted it will explode, covering any nearby survivors in Bile.

The Survivors
When dealing with the Hunter, there are a few rules of thumb and things you need to keep in mind:


 * Always have at least one buddy close at hand.
 * Listen for the distinctive growl the Hunter makes when he is crouched and ready to pounce. Once you hear the cues, remind the other Survivors of the Hunter's presence to keep everyone on their toes. This may sound useless, but it often prevents Survivors from taking unnecessary damage from Hunters.
 * Remember that the Hunter won't always pounce as soon as he sees a Survivor, be it an Survivor Bot or a player-controlled one. Even the Bot waits and bides its time. As a Survivor then, your focus should be on progressing, not finding and killing the Hunter. This is especially true in Versus, where Hunter-players will often simply fly around the map with the hope of distracting and delaying inexperienced Survivors.
 * On higher difficulties, and in Versus, the Hunter will often use their claw attack instead of pouncing the Survivors. This attack can be devastating, because oftentimes Survivors will not realize that a Hunter is present until it is too late. The Hunter emits no sounds while standing, and in larger hordes it tends to blend into the crowd. As a Survivor then, it is critical to watch your team's health meters during large horde attacks. If someone's health meter drops unusually fast, it is usually an indicator that a Hunter is attacking nearby.
 * When a Hunter is growling, this means that he is ready to pounce. It is easy to cause head-shots on him and kill him instantly. If he gives off a loud screech, he's spotted you and can pounce you (only when he's crouching)
 * If the Hunter is outside pounce range, open fire. Head-shots are particularly effective.
 * Otherwise, shove just as the Hunter starts his pounce. This will knock him back with a stun, and allow finishing him with your choice of two additional shoves or weapon fire.
 * If you manage to stop the Hunter mid-pounce, keep hitting him as this keeps him from doing anything. Definitely use this tactic when he is close to other Survivors to avoid friendly-fire.
 * Be very careful when attempting the above tactic. An Infected, AI or otherwise, can still claw you while it's stumbling backwards. This is extremely dangerous on Expert difficulty where any Infected's claw attack can cause massive damage, especially the Hunter.
 * In Versus mode, be very careful of the Hunter or any other Special Infected visible standing behind red, alarm-triggering cars, the Survivors might be tricked and lured to shoot them.
 * AI Hunters will jump if shot at, pouncing or not. This leaves them vulnerable to attacks as they can't move until they land.

Once a Survivor is pounced:
 * You will receive a visual notification that a fellow Survivor has been pounced on.
 * Shoot at the Hunter if you are far away and melee it if you are close to it, friendly fire does not hurt a player while they are pinned down (although once the Hunter is off, they are then vulnerable to such).
 * If too far away and there is no Survivor closer than you are, go ahead and shoot.
 * Be careful if the Hunter is on fire, as they do more damage, and can bring down your health very fast.
 * A head shot with a shotgun or a sniper-type rifle will kill a Hunter in one shot.
 * Don't let walls stop you. If the only way to save a fellow Survivor is to shoot through a wall or ceiling, do it. A hunting rifle is particularly effective at this, although any weapon can penetrate walls.

The Infected
The Hunter excels at picking off any stragglers or lone Survivors in any team. A Hunter's pounce pins a Survivor, leaving the victim completely helpless and doing the quickest damage to a survivor of any infected (except the charger, if the player is not incapacitated), until the other Survivors melee the Hunter or effectively kill it. Otherwise, without another Survivor's intervention, the pinned Survivor will die.


 * Due to the fact that the majority of players travel together, Hunters will not commonly find stragglers. This behavior by the opposition means that Hunters generally cannot successfully initiate an attack and cannot expect to do serious damage. As a result, Hunters are best sent in during a Panic event, when Survivors are blinded by vomit or bile, or any other cases in which the Survivors' attention is focused elsewhere. This lack of opportunity means that Hunters must stay stealthy and hidden until opportunities present themselves.
 * In order to pounce, Hunters must remain crouched for a limited time. However, being crouched makes the Hunter growl loudly, broadcasting his arrival on the scene to any nearby Survivors. Also, whenever Survivors are in view of any of the Special Infected, the Special Infected will emit auditory sounds, such as aggressive growling in the Hunter's case, though Hunters are silent when standing still and not crouching, a trait unique only to them. To avoid this, Hunters should remain standing and out of sight until they are ready to attack.
 * One of the Hunter's best attacks, that is infrequently used, is a straight claw attack by the Hunter in a standing position. This attack can deal a large amount of damage in a short amount of time. It is much less noticeable than the pounce attack allowing a slightly longer time to deal damage. This attack should be used if the group is bunched together facing in the opposite direction or during the confusion of a Boomer attack. An advantage to this method is that the Hunter does not shriek. This allows being stealthier and easily mistaken as one of the Common Infected. Another idea is to use this attack to quickly incapacitate a Survivor in the red; one or two hits and they'll be on the ground.
 * Another effective tactic is to continuously wall jump. Hunters emit a distinctive scream during flight. An experienced wall-jumper can effectively distract a team, slowing them down, and buying the Infected players additional time, which may cause the Director to spawn a Horde. Also this can be used to tempt someone to stray away from the group to kill the Hunter. Then when he is alone, pounce on the lone Survivor.
 * If you do not rely on your teammates hunters (and Spitters) can go solo, stalk the Survivors by having them in range and sight, when the time is right, jump in and cause massive damage.
 * Hunters work significantly better with a meat shield (the horde, Charger, Tank).
 * You can insta-pounce without crouching by backing up into a wall and while still backing up, jump. You can then jump off the wall as you would a regular wall-jump. Obviously this is useful for not giving yourself away, but also extremely useful for making quick escapes if shoved off a Survivor. This has been confirmed in both L4D and L4D2.
 * If the Survivors don't seem likely to spread apart, you can try to inflict damage with high damage pounces. If a Hunter pounces from high enough and far enough away, the survivors will be slammed into the ground harder, inflicting up to an extra 25 damage if the pounce connects.
 * A Hunter's pounce can stumble any survivors nearby. This can be used to push them off a ledge and force them to hang or even push survivors into traps such as fires or a Spitter's acid.

The Survivors
Here are some basic tactics to help you deal with a Smoker:


 * When you or one of your teammates hear a Smoker, stay close together and watch out for each other. If any of the Survivors are alone and too far away from the group, they make an easy target for the Smoker. If the lone Survivor is grabbed, it's possible the other Survivors will not notice or will be too far away to help in time.
 * If a Smoker is on a roof and has grabbed a teammate then do not waste your time killing the Smoker and just shove the Survivor. The Survivor will automatically be freed. This is only recommended if you plan to weave through the map, as a Smoker that lasts longer in-game will be more dangerous over time, especially if you bump into a Tank.
 * If you see a Smoker and you're near a wall, hide behind the wall if the Smoker is in front of it. This will stop him from snaring you and you can shoot back on him as this restarts his timer on ensnaring you.
 * When a Smoker chokes a target, they are very easy to kill. A few shots from any weapon kills them easily.
 * Smokers tend to attack from behind or above your location, but some will spawn in front of you, so move carefully if one spawns.
 * When a Smoker grabs you, you will have a few seconds to free yourself by shooting the Smoker. If you are not currently holding a gun (or have started reloading) at the time you are grabbed, you will probably not have time to save yourself.
 * If a Smoker grabs you while you're throwing a pipe bomb, and no other Survivors are around or notice you, throw the pipe bomb at the Smoker. The resulting explosion will free you from the Smoker's grasp.
 * If you have a Chainsaw, when you are grabbed by the Smoker, use it to free yourself.
 * If have a Melee weapon on your hand slash directly at the tongue at the right time otherwise if Smoker grabs you before you can swing your unable to swing again and you will be force to switch to your Primary weapon, However if the smoker is up close you can switch your Primary weapon and bash before he starts attack you. (You must have a Slash, Shredding type Melee weapon to work such as Fire Axe, Machete, Katana and etc) (Note: Chainsaw will hit the tongue no matter what)
 * Smokers are extremely dangerous on Expert, dealing 40 damage per hit when constricting a Survivor. It should be imperative to save constricted teammates immediately, even if you will take damage from Common Infected. Left unchecked, a Survivor at full health will be incapacitated in 3 seconds and die in 8.
 * However, a survivor being dragged toward a Smoker will not take damage as often as a fully ensnared Survivor. Although an exception of this is during Versus mode.
 * If this happens while Common Infected are attacking you, face the game camera away from the direction of the Infected. Even though you may still be dragged, if done properly you will be taking less damage from them, especially on harder difficulties where health is extremely important.
 * If you know where a Smoker spawns, "force" it to ensnare you. Once the Smoker sends out his tongue (he will also make a loud sound when he does this), immediately hide. The tongue will be unable to follow you and leave the Smoker helpless for several seconds, which should be more than enough to kill him before he manages to hide.

The Infected
As a Smoker your job is to ensnare a Survivor and separate them from their friends, leading the ensnared survivor to danger.


 * Your tongue attack leaves Survivors helpless after about two seconds of being ensnared. A seasoned Survivor with quick reactions can break himself free from your tongue and kill you most of the time. However, a well placed attack in the midst of a horde rush can spell disaster for the Survivors if not dealt with properly. Always look to be either up high or in a dark place as the darker or higher you are the less chance the Survivors will be able to shoot at you, and add the possible effect of common infected hitting the Survivor while he's smoked, a sort of Piñata effect.
 * An experienced Survivor can recognize the wheezing and coughing of a Smoker and will be alert and ready to save his teammates from being snared. If you want to be a real burden to the Survivors, stand in front of or behind an alarmed car. If you stand by the car and pull a Survivor over to you, the other Survivors will have no other choice but to try and save the person you snared. Generally, instinct will override common sense, and the Survivors will open fire, inevitably activating the car's alarm. Any stray bullets that impact the car will set the alarm off, attracting the horde, and buying you more time to attack.
 * This tactic also works similarly well with the Witch.
 * Good Smoker players excel at using the environment against the Survivors — this can be done by dragging them down from a higher part of a level as the fall will do a lot of damage, and in some places it will cause death. If the lower area is just where the Survivors have had to climb up from, the Smoker's target will have to climb back up to the higher area leaving them away from the group and slowing down the team. Smokers can also drag Survivors through fire that again causes large amounts of damage while either forcing another Survivor to run through the fire to release their constricted teammate or wait until the fire dies down while the Smoker does damage to the constricted Survivor.
 * In the Dead Center Hotel level, the fire in the middle of the room next to the area with the safe room does massive damage and has debris to keep the survivor from being pulled through it to you. Hazards such as this can be useful to quickly kill a distracted Survivor during a horde.
 * Combine the abilities of you and your teammates:
 * Smokers can drag a Survivor through a horde, creating a passage. The same passage can be used by a Charger to scare off the Survivors who rush to help their ensnared ally.
 * Smokers can also be used to position a survivor in front of a window, so a Charger can ram the Survivor off and instantly kill him.
 * If you manage to drag a Survivor away from their team, urge a Spitter to spit or a Boomer to vomit on the Survivor you are choking to speed up their loss of health.
 * The boomer bile would be especially helpful, since the Smoker does very little damage to incapacitated Survivors and the Infected do 5 times more damage than normal to them.
 * As always, think like a Survivor, imagine the worst possible scenario, and make it happen!

The Survivors

 * Use melee shove to knock Jockeys off. They will be stunned so you can shoot them.
 * Keep moving so you are a difficult target to pounce on.
 * Watch the rear or front stragglers for Jockey attacks.
 * If available, use a grenade launcher (not the best idea on Expert). It will knock the Jockey off in a stumble, much like a shove but more damaging (to both the jockey and survivor).
 * Head-shots deal heavy damage to the Jockey. Shoot them by angling your gun a little down or crouch shooting them. If they get close, spray them with gunfire.
 * If a Jockey gets close, move back and then melee it. Moving back will prevent the Jockey from riding you and meleeing it will stun it and allow you to kill him.
 * Although this is usually ill-advised (especially on Expert difficulty) since a Jockey will can use their claws at you or can pounce at you if you did not melee shove them in time.
 * Jockeys are one of the weakest Special Infected (dealing little damage with their special attack), but they still shouldn't be underestimated as they can still cause a lot of trouble to the team.
 * However, prioritize Jockeys if there are any hazards nearby, such as fire or areas that a Charger could death charge the survivor off of.

If you are pounced by a Jockey:
 * Simply put, resist! Move in the opposite direction of where the Jockey is steering you. This will make you move extremely slowly, allowing teammates to come and knock the Jockey off. It is also useful if a Jockey is steering you towards danger, whether it'd be a horde hungry for your flesh, a puddle of Spitter acid, or just towards a ledge, this will most certainly allow you to get valuable time for teammates to help you, rather than doing nothing and most likely, die.
 * While being pounced make sure you're looking at the opposite direction at your teammates so they can kill the Jockey faster than looking at them if they don't know about bashing the Jockey or too far away from you.

If your Teammate is pounced by a Jockey:
 * The best option is to bash the Jockey before you shoot because it can be impossible to shoot at the distance as your teammate who is pounced can be in the way if their looking your direction

The Infected

 * Your goal is to jump on a Survivor and steer them off a tall edge, into an area their team members can't get to easily, or somewhere far behind that will stall the team and damage the victim.
 * Move around a lot amongst the Survivors. You are pretty fast and can get them to shoot each other.
 * Slash with your secondary attack to decrease health while moving.
 * Once you jump on a Survivor you are a target, so try to coordinate your attacks or jump on someone who is low on health. Once you incapacitate them you can move on to another target.
 * The Riding My Survivor mutation is an excellent place to practice Jockey tactics.
 * While riding, steer the Survivor into Spitter acid or other hazards.
 * Take out anyone with a melee weapon first as they can instantly kill you.
 * You can also steer a Survivor to a Witch, or hide behind her with your incapacitated Survivor. It will be a very hard choice for the Survivors to shoot at you.
 * A shoved-off Jockey can jump again sooner. Use that to your advantage.
 * You can also use the high buildings to fall onto Survivors from above. The best way is when the roof is just above the door. Wait for all of them to leave and then quickly fall on the last one and grab him inside. A successful attack will really slow down the Survivors.
 * Even if the Survivors are clumped together, you can still cause confusion by quickly grabbing a Survivor and steering them behind something, forcing the others to chase after you and save their pal.
 * Steering the Survivor off a cliff can slow down the team even more, and a Charger could easily take a rescuer.
 * Steer Survivors in front of high up windows that a Charger could plow the Survivor through. This can very quickly and effectively kill a Survivor, but the tactic is inconsistent.
 * If you hide behind an object that cannot be jumped on top of, move around it when Survivors chase after you. You can waste their time and health with a bit of humiliation thrown into the mix.
 * If you are high up and drop down without jumping, you will still ride anyone you land on. This can be used in the same way a "Rocket Boomer" is used, by running forward, jumping and spawning in mid air, and launching yourself at the Survivors, landing on a head and riding them into the sunset. Though difficult to do, this tactic certainly wouldn't be expected.
 * Use Tanks as meat shields when you ride a Survivor. The Survivor is unable to help the fight, the others can't help him without going through the Tank first, and if you get knocked off, the Tank has a chance to finish the job.

The Survivors
General Tank tactics:
 * If an AI Tank is still idling (say, it is in a room raging and pounding its fists as usual) and is unaware of your position, you can surprise it by throwing a Molotov or igniting a nearby gas can on it.
 * Keep your distance from the Tank if at all possible. You can't expect to survive a one on one with a Tank unless you have a decent amount of health and are an experienced player, but having to go one on one with Tanks should rarely happen. Take advantage of your surroundings by climbing up and jumping off of ledges, as the Tank leaves itself open whenever it has to climb.
 * In Left 4 Dead 2, the tank no longer attacks incapacitated players. Once he downs one, he will immediately change targets. On Expert, this is especially deadly as he can quickly reduce even the best teams to dust. If one, two, or even three players get downed, it is imperative to pick them back up. Have one player distract the Tank while you pick your fallen friends up. It's much easier to kill a Tank with 4 people shooting it rather than only 1.
 * Set the Tank on fire by using either a molotov or a gas can. As of January 23, the damage the Tank receives from fire is now reflected in the Tank's health. This will reduce the amount of time that's required to engage and defeat the Tank.
 * Explosives such as pipe bombs, propane, or compressed air tanks are great for limited big damage, but not as effective as fire, which always does guaranteed damage over time to the Tank. Propane and Oxygen tanks will also knock the Tank back, like most other Infected after a melee attack.
 * Keep clear of cars, fallen trees, furniture, and dumpsters if the Tank is nearby. The Tank will definitely use big objects in the environment and try to punch these objects towards Survivors, which means an immediate incapacitation if said object hits any one of them. Tanks will try to climb over burning barrels, though, setting them ablaze (usually only applies to AI-controlled Tanks, but might work with some similar smart players), so moving to put a barrel between you and him will usually have the same effect as a well-placed Molotov. Make sure you run, because you do not want to be pounded on by a burning Tank.
 * Try to draw the Tank into a crouching only area. It can buy you a few seconds while the Tank tries to wiggle its way through. Good examples of crouching-only areas are ventilation grates, windows and ambulances.
 * Note however that this is no longer a viable tactic as of the latest update. Tanks now crawl at a much faster speed and will quickly overwhelm a team hiding in vents.
 * It is very effective to make a Tank go through a window, slowing it down, and when it is almost crossing it go to the other side to make the Tank slowly cross it again until it dies. This can deal a lot of damage to the Tank or even kill it leaving the Survivors unharmed. This can be done with the windows of the main buildings in the No Mercy, Death Toll, and Blood Harvest finales.
 * The Tank can climb, but it slows down. Take advantage of this as you can climb up and down much faster.
 * In closed quarters, all Survivors should concentrate all of their fire-power on the Tank. The Tank will pound on a Survivor or two, but everyone should make it out alive.
 * Another useful tactic is to get to an area immediately inaccessible to the Tank. The rafters of a building away from the area that allows one to climb up to it is effective, because the Tank wants to get to you by the shortest route.
 * Whenever a Tank takes damage, its forward momentum slows down (just like yours do when Infected hit you). If you can light him on fire, hit him with a minigun, and have the other three pump Shotguns into him, the Tank slows to a virtual standstill and is quickly dealt with.
 * Lacking a good situation, have one person focus on avoiding the Tank while the other three keep him as slow as possible. Make sure to communicate and let your bait know if he switches targets.
 * If the Tank throws a rock at you while you are strafing, immediately switch direction — the Tank throws the rock to where you'll be, not where you are.
 * It is possible to force the Tank to drop a rock by shooting the concrete as many times as possible whilst it is still in the Tank's hands.
 * On Expert difficulty, the Tank can incapacitate a Survivor with one punch or his rock throw. Once a Survivor gets incapacitated, they will die in two hits so keep your distance and stay on your toes.
 * Never let the Tank back you into a corner as you can't go anywhere, and most likely you will be taken down.
 * Explosives deal around 750 damage to the Tank.
 * If you are using a generally inaccurate weapon and/or don't like to move while shooting or to dodge a Tank's concrete slab throw, take cover in an ideally medium to big area of cover (small will do; just crouch). While you reload, head back into cover, then pop out, burst fire, then duck into cover if it throws a slab. If you see that everybody's retreating or that a horde's coming and everybody's too busy with the Tank, cover them and try to alert a player that either a horde or a Special Infected is coming.
 * It is also possible to block the way of a Tank by stopping in the middle of a ladder the Tank has to go through to damage the Survivors. The ladder has to be in a 'tunnel' where the only way out of it is either up or down, not sideways. Your other teammates can freely shoot the Tank but they have to be careful not to shoot their friend since the last thing they want is to incapacitate him and let the Tank successfully climb the ladder. This can be done, for example, in the exit ladder of the Sewer in No Mercy. This tactic works better on AI Tanks since they're usually won't jump off ladders (or do it quite late), so you will have plenty of time to pour it on.
 * If you see a Tank starting to throw a rock at you it's possible to shoot his rock before it can reach you by shooting the rock in mid-air, but you need distance yourself as the rock can reach you before you can even destroy it, But here are the easiest weapon to destroy his in mid air are AK-47, Combat Shotgun, Auto Shotgun, Combat Rifle and Hunting Rifle/Sniper Rifle it also can work on any difficulty and also good for if your in bad situation such as low on health or in tight spots. (Any weapon can be possible but all their shots must land to destroy it)

If someone else is attacked by the Tank:
 * If the Tank is pounding a Survivor into the floor, another Survivor can aggravate the Tank and possibly draw its attention from its target by shoving and hitting it in the back. Shooting a Tank won't have the same effect as tapping it on the shoulder with your gun's butt when it's busy killing your teammate. Be aware that a Tank can turn around mid-swing and smack you if you're trying to shove him.
 * Another way to aggravate the Tank and draw its attention is to get on a nearby mounted gun. Even if you can't hit the Tank, he will stop pounding on the incapacitated Survivor, and go after the gunner. Another Survivor should then try to help the downed player up as soon as possible. The only downside to this is that they only appear in very few chapters.
 * Never let the Tank back any of your teammates into a corner as they can't go anywhere and it is most likely they will be incapacitated.
 * Melee weapons deal 500 damage per swing at the Tank, regardless of what type. You can easily reduce a Tank on Expert difficulty this way, although you will need to switch from helping your incapacitated player and swinging on him as they can usually bypass this, but AI Tanks on L4D2 will always target incapacitated players if they can.
 * If you have pain pills and someone else's health is in the red, give it to them. This can prevent them from getting incapacitated. Also, if someone's health is above 40 %, they can outrun the Tank. Pills provide 50 % health boost so giving pills to weaker Survivors will let them run faster.
 * If a teammate is incapacitated and you don't want to change his target to yourself, you can do one of two things:


 * A) Fire away until the Tank dies, although on Expert he will most likely kill the incapacitated player before the Tank itself dies.


 * B) Run, especially if close to the safe room. If all the players can get to the safe room and close it while the Tank is killing another player, you will succeed.


 * C) If you are the incapacitated player, don't be afraid to shoot at him with your pistols. Every little bit helps. It can really mean the difference between the Tank dying on your body, or you dying under the Tank.

The Infected
The Tank, one of the most dangerous Special Infected by far, is able to withstand lots of punishment and can incapacitate Survivors in a few punches. In Versus, the Tank is given out at random but usually goes to the two players with the highest points. When you get the Tank you will usually spawn ahead of the Survivors. Start running towards them as soon as you spawn for two reasons: As a Tank, you need to use the environment to your advantage. Punching certain objects — they will glow red to show that you can punch them. Punching the object at Survivors will cause an automatic incapacitation on impact. In a choke point, such as the alleyways of No Mercy which mostly have dumpsters or cars, this can be devastating, scoring an instant win as all the Survivors are incapacitated in one hit. It's also possible to knock objects into the alleys in such a fashion that it effectively blocks the Survivors path, dooming them to a premature grave. However, if you die before the Survivors do, and their path is still blocked (e.g. if the door next to the police car is blocked on Dead Center Streets), the obstacle will only last a minute or so before it despawns and allows the Survivors to pass.
 * 1) The Tank Music will play and the Survivors will prepare for a Tank, meaning you do not have the element of surprise.
 * 2) The "Control Effect" or Frustration Meter. If you do not hit the Survivors with a rock or your fists, your Frustration Meter will go down. When it is completely gone, your control will be given to someone else. Eventually, if two or three people lose control in this way, then control will be given to the AI Director.

On all finales, after each horde spawns, a Tank will spawn. This will happen twice before the rescue vehicle arrives. Once the rescue vehicle arrives, another Tank will spawn, and that will be the Infected's final chance to finish off the Survivors.

If possible, try to punch Survivors off rooftops for an instant and free kill. Remember to always look for a lone Survivor as a Tank! If the others run off but one is trying to heal or gets trapped by Infected, score an easy incapacitation and lower the Survivor count! They won't be able to get far, but if you're running at all of the Survivors and they're all firing continuously at you, your speed will be dramatically reduced and they will more than likely kill you before you can do any real damage.

Fire is the Tank's worst enemy. If the Survivors manage to set you on fire you will eventually die no matter how much they shoot you or how many you kill. After being set on fire by a molotov/gas can, you will begin to slowly lose health. A Tank at full health that has been set on fire will die in thirty seconds, so avoid fire at all costs! However, if you are near a large body of water (e.g. at the Death Toll Finale) you can jump in and put the flames out.

Do not punch any Survivors already pinned by Special Infected, or you will kill that Infected, (unintentionally) free the Survivor and possibly save their life. Instead, aim for any Survivors attempting a rescue and give the Hunters/Smokers time to at least incapacitate their prey. Safe room doors can be destroyed by the Tank, but only the ones at the beginning. You cannot destroy the Safe Room door at the end to prevent the Survivors from winning.

Most bullets cannot penetrate the Tank. Sometimes it is useful to purposely put yourself in between free-standing Survivors and one that is pinned by a Charger, Hunter, or Smoker. Tanks are also meatshields!

Roll in and make an attempt to separate the entire team by:


 * 1) Throwing a concrete slab.


 * 1) Running in and hitting a Survivor (blasting them back).


 * 1) Knocking a heavy object into the middle of the group. If you do this with a Charger, it will make your job easier.

Doing this can pretty much destroy the Survivors; but if you don't, more of your teammates will roll in as well, killing any runners.

Witch
Here are some basic tactics to help you deal with a Witch:

The Survivors

 * Turn off your flashlight.
 * The Witch has a red glow around her head which helps to identify her quickly in a large group of Infected.
 * Note that music gets louder as you get closer, and gets quieter as you are farther.
 * Do not shoot at or near her; loud gunshots near her will get her attention.
 * Advise allies if you locate her, and give them the precise location.
 * Memorize the general area. If you end up startling her, and then shoot while backing up, you don't want to fall off a building or run into a wall.
 * Try to get past the Witch; don't start a fight unless you absolutely have to, such as in Expert Mode where the startle time is too low for players to pass through.
 * If you absolutely cannot get past her, your only option may be to fight her.
 * Never startle the Witch in Single Player Expert or Realism Mode. The AI will most likely not be able to deal with her before she chases you down and kills you. Go around her unless there's absolutely no way to avoid startling her.

Defeating the Witch:
 * First, try to "cr0wn" her with a Shotgun. For best results, use an Auto Shotgun or Combat Shotgun. First is to position yourself behind her. Run right up to her, then aim at her back or head and spam the fire button. Aiming at her back has a larger area to shoot at, while aiming at her head does more damage, but is a smaller target area. If she doesn't die in the first shot, the next two or three should kill her. An alternate idea would be to place a propane tank next to her, and detonate it.
 * Wandering Witches are far easier to kill, since there's a small delay before she attacks the startler.
 * You can stun the Witch BEFORE she gets to move by shooting her in the head with the Sniper Rifle or Hunting Rifle. She will go down usually in one magazine of the Hunting Rifle but if she doesn't, it still gives you and your team adequate time to put her down.
 * Another strategy relies heavily on the environment: if you can quickly put a closed door and a gas can between you and the Witch, you can passively kill her without any damage to yourself. First, place a gas can on the opposite side of the door to the Witch, then shoot her. Quickly shut the door and run as far away as possible. When the Witch breaks down the door, she will destroy the can and burn herself. When this happens, she 'forgets' to attack players.
 * When using a chainsaw, it is possible to charge the Witch and kill her without taking damage.
 * Be extremely careful when trying to cr0wn the Witch or kill her with a chainsaw in Versus, as Infected players will very likely attempt to "pin" the killer (Or if very organized, pin the other three Survivors so the killer will have to choose between rescuing them and risk startling the Witch or killing her first and letting the Infected heavily damage the other Survivors). If she can't be avoided, killing her from a distance may be safer.
 * Try not to attack the Witch if there are undistracted Commons nearby, especially in Versus, as a Boomer/Hunter combo can be deadly to the killer (The Horde, Hunter and Witch all together will kill a downed Survivor in no time).

If you startle the Witch:
 * If she doesn't die, burn her with a molotov; that way, her health will continuously deplete, as well as slowing her down slightly. The slowing effect is more noticeable on Left 4 Dead 2.
 * Run back to the safe room as she can't break down the door, then when you are safe inside, reload. This is not possible in Versus, as the safe room door cannot be closed after being opened. Witches, however, retreat upon players reaching the safe room, either the end one or the start one.
 * DON'T STOP MOVING ! The Witch, though strong, is not slow. She is actually quite fast (300 speed compared to the Survivors' 210) and will most likely catch up to you if you stop to take a shot, so don't stop running.
 * If forced to run, use adrenaline to increase your running speed.
 * DON'T STOP SHOOTING! If you have a hunting rifle, shoot from afar; if you have a shotgun, get up close, but keep a distance. Witches tend to make a beeline on you, not moving directions to make you lose your aim, so spray her quickly with your ammo.
 * Have a trustworthy ally next to you in case she incapacitates you.
 * If possible, use heights to your advantage (Example: at the top of a ladder). That way, if she climbs to get to you:
 * 1) Her attack is delayed.
 * 2) You have an excellent chance to get some head-shots.
 * 3) You can just keep running.
 * Find a ladder if possible! Stay on it and the Witch can't attack you. This also gives your teammates some time to shoot her.
 * On Expert, if possible, incapacitate yourself by some means (e.g. ledge hanging, etc.). While the Witch is still capable of killing you in one hit, she has a two-second delay before she attacks an incapacitated Survivor, which can be more than enough time for your teammates to save you.

If someone else startles the Witch:
 * Make a defensive line between the Witch and the one who startled her, and unload before she gets to them. If she is not killed, then her health will be low enough for the running Survivor to kill her.
 * If you have a Shotgun, keep shooting her up close; she won't attack you unless you directly block her from moving (If you block her in an open area, she will just push you out of the way while charging, not causing damage).
 * Throw a propane tank at her and shoot it. This will hurt the Witch, as well as push her back a few feet, delaying her attack and sparing your teammate.
 * If you are in a tunnel or other confining space, do not stand between the Witch and her prey. She will get frustrated shortly and kill you instead.
 * On Expert, the Witch ignores incapacitation and instantly KILLS her target. If a teammate has startled the Witch, incapacitate them immediately (unless they are on their last "life). Even though the Witch can still kill them in one hit, she has a charge up delay when she attacks an incapacitated Survivor. Make sure you have a weapon to kill her quickly or your attempts will be in vain.

What not to do when startling the Witch:
 * Though it is smart to close doors behind you because it will delay Infected and Special Infected, this will not stop a Tank or a Witch. If you are being chased by the Witch, she will rip the whole door down with one attack. One can drop a gas can behind a door while running from the Witch to ignite her, which will also cause her to stop attacking whoever startled her.
 * Don't split up, the Witch will only go for one person; the others are completely safe, so if everyone runs in separate directions, the one who startled her will most likely be killed by the Witch, and the others may be killed by other Special Infected, so stick together!
 * Don't shove the Witch (if she hasn't been stumbled with explosions) — except with the Chainsaw, and only do so if you can sneak up on her.

See the Witch for more tactics.

The Infected
Although you cannot play as the Witch, you can certainly use her to your advantage:
 * Smokers can drag Survivors to the Witch.
 * Hunters and Boomers can crouch in front of the Witch, obscuring her from the Survivors' sight. Alternately, if a Boomer dies while the Survivors are relatively close to the Witch, the explosion will startle her, sending her after the person who killed the Boomer. It is also useful to duck behind her as they will not risk trying to kill you if it would alert the Witch
 * If you pounce a Survivor as a Hunter while the Witch has already incapacitated someone and is attacking, you will not be damaged and the Survivor will die twice as fast. You will also get points for the damage she inflicts.
 * Experienced Hunter players normally crouch just out of sight near the Witch, waiting until a player runs up to attack the Witch and pouncing them just before they get a chance to fire. This gives the Witch the potential to do the most damage, possibly even killing the Survivor if timed properly.
 * Most experienced Survivor teams will have three players take up defensive positions while one goes up to "cr0wn" the Witch. As a Smoker, you can strangle the player who was tasked with Witch killing just as they are about to cr0wn her. The Witch will be startled, and the Survivor is basically a sitting duck.
 * Another good tactic as a Hunter, when possible, is to hide (standing) near the Witch, completely out of view of the Survivors (perhaps even waiting to spawn until they are close). When a Survivor is close enough, run out and slash the Witch once. She'll be instantly upset and attack the nearest Survivor. This tactic (as long as you stay hidden) does not give away your position (due to not making a sound) until the critical moment, and usually allows you to retreat momentarily and then proceed to pounce a Survivor trying to rescue the one incapacitated by the witch.
 * An Infected player can claw the Witch just as she looks up when a Survivor gets too close, sending her after them. The Witch has 1000 health in Versus, so any damage she takes from clawing is generally insignificant unless sustained for long periods of time.
 * An effective method is to have all of the Hunters surround and circle the Witch as if guarding her. Upon confrontation or encounter, the Survivors will be discouraged from advancing, knowing that the Witch is both dangerous and heavily guarded by its weaker counterparts.
 * The Jockey and Charger can quickly move a Survivor towards a Witch. In the case of the Charger, an even more destructive possibility may occur. If the Charger was killed, then the Survivor would both be freed... and be a likely target for the Witch. If the Witch was attacked before the Charger was, the Witch would both incapacitate or kill one Survivor, and free up the Charger to do much more damage.

The Survivors
This game hates lone wolves like no other. You need teammates to cover your back and pull you out of tough situations. There are a few tactics and tips you should keep in mind:

Power in Numbers: As long as the special Infected outnumber you, chances are that they will get a combination that can leave you and your team helpless. On the other hand, if the Survivor team outnumbers the Infected team, these are the only outcomes that could possibly lead to everyone being downed.
 * A Tank, Spitter, or Jockey attacks.
 * The players that are not helpless are attacked by a horde.
 * Friendly fire, such as a poorly-thrown molotov.
 * The team fails to kill a Witch before it flees.
 * One or more Survivors falls victim to an instant incapacitation or instant kill attack (Being charged, knocked, or pulled off a ledge or out a window, etc.)

Healing: Most healing is done when not needed; For example, if you have 30 bleed-out health (like after revival from incapacitation), do not heal. Instead, take pills or adrenaline. On easier difficulties, pills and adrenaline are not so common, while there are more first aid kits, so when out of pills or adrenaline, using a first aid kit when health is around 40 or lower is advised. On harder difficulties, as pills and adrenaline appear more common, while first aid kits are more scarce, you should wait until after your final incapacitation (when your vision becomes monochrome), because a First-Aid Kit can cure that and save you time. Try to use health kits during Crescendo Events or after a horde only if needed. If you just got up from being knocked down and you are in a finale or horde, take your Pills or Adrenaline to cover your healing time so you do not get knocked down again while healing.

Voice Chat: Voice communication is extremely useful and most players will need to use it to ensure survival. It is not a requirement, but voice communication is a lot easier than using the message chat and it will help teammates know what is going on around them while normally offering them a quicker rescue response from special Infected and being incapacitated.

Turn On Closed or Full Captions: If you turn either of the above on by going into options, the game will say things like "Tank growls" or "Incoming Attack". Although not necessary, this will help a lot to new players. Turning on captions can allow human players to know of incoming Special Infected even if normally out of audio range either by in-game design or volume.

Single File: This tactic is best used in a narrow or confined space, such as hallways or tunnels. The players with the most health should cover the front and rear, while the players with the least health stay sandwiched in the middle. There should be plenty of space for two Survivors between each player, so if one is pounced/grabbed, the other players won't be knocked back, and can aid the Survivor faster. This is not a good idea to perform in Left 4 Dead 2 when a Charger has spawned, because he can easily barrel through the Survivors and cause major damage.

Moving: One of the most important things to do on Expert Difficulty is to always keep moving forward. On Expert, the Director will almost constantly send hordes and hordes of Infected at immobile Survivors. The longer you take through a level, the more hordes and Special Infected you will need to face, so move quickly and cautiously.

One very important exception is during a horde attack. Find a spot to cover your back, crouch, and do not move! This helps to reduce team damage. If in the open, you can use a teammate's back, so that you each cover 180°.

In Versus mode, if you are not firing a weapon or shoving and you are either crouch-walking, walking or standing still, your outline will not be seen by the enemy Infected. This is very useful for sneaking up on a position where a Special Infected is likely to be hiding. Note that this will not apply to Survivors in sight of Infected players or Survivors covered in Boomer bile.

Weapon Selection: Because of the variety of threats and the variety of weapons available, it is advisable to have different members of your team with different weapons. Some threats come from nearby and are best dispatched with a melee weapon or a shotgun, other threats are from farther away and are best hit with a sniper rifle. The environment also comes into play, as some weapons are capable of shooting through walls and others are ineffective behind walls. It is best for your team to have a mix of close- and far-quarters weapons, and ideally each team member will have something that is capable of hitting both near and far targets. If you prefer an auto-shotgun as your primary weapon, it might be advisable to take a magnum instead of a melee weapon so you can potentially rescue a fellow Survivor pulled by a Smoker. Likewise if you prefer a sniper rifle, you could find yourself in real trouble without a melee weapon if you get surrounded by a horde. A team with all shotguns or all sniper rifles is far less balanced than one with a good mix of armaments. Depending on your team dynamic and player skill, an effective mix might be one sniper rifle/melee, one assault rifle/melee, one assault rifle/2 pistol, and one shotgun/magnum (for example). The same idea goes for the throwable weapons as well. Try to have a good mix of pipebombs, bile bombs, and molotovs. Knowing when to use these items is equally important. Use the pipe bomb during horde attacks, when a survivor has been vomited on, or to clear out large open areas so the team can move faster. Use bile to slow down a tank, draw common infected away from players, or paired up with environmental hazards such as fire because the common infected will rush into the fire and be set ablaze. Use the molotovs to light the tanks on fire but be aware that it will move faster once alight and to cover a choke point. The molotov is very useful during crescendo events because if the team has to move from one area to another, such as in the mall to shut off the alarm, the person in the rear of the group can throw a molotov into a choke point behind the survivors, the fire should engulf the total area of the choke point and block any infected from coming at the survivors from behind.

Don't be afraid to vary your weapon selections either, depending on what becomes available. If you think there's a tank coming up ahead, it might be a good idea to pick up an AK47 or auto-shotgun when you come across one, even if you have to go back and pick up your laser-sighted sniper rifle when you're done.

Left 4 Dead 2 ' s Grenade Launcher is not very useful on most maps when playing in Versus mode. Its accuracy is dubious, the reloading is slow, the ammo is limited, and the potential for friendly fire damage is high. It is most effective for hitting large groups of common Infected from some distance away, and those situations don't often present themselves outside of finales. Given the potential for friendly fire in close quarters though, it's not a good primary weapon for a finale either. The grenade launcher can do a lot of damage with one shot, but when you count in the reload time it's very possible to do more damage to a single target (such as a Tank) in the same amount of time with almost any other weapon in the game. In versus mode, the Grenade Launcher is best used temporarily during a panic event or for taking out a horde during a finale, and then swapped out for something that makes less collateral damage.

Team Formation: Some players prefer to rush and go gung-ho against the Infected, while some prefer to take the precautionary measure of taking one small step at a time. Another group of players prefer to act as the mediator between the two, constantly going back and forth to look out for players who are more audacious, and those who are more cautious. The combination of these three distinct groups of players affects the overall behavior and performance of the team. A team that has four rushers would probably finish up a map fast; but their disadvantage is that some difficulty levels cannot be rushed. A team with only rushers and cautious players might find themselves frustrated if those in front, or those behind are pounced or ambush, leading to the team's defeat, and the eventual disintegration of the team due to friction. Depending on what type of gamer you are, different combinations suit you differently. There is no correct way to play the game; so players who are competitive and quick-paced may prefer four rushers, while those who take satisfaction at teamwork and coordination would prefer a group with all three playstyles.

Squad Formation: An effective tactic, especially in tight quarters, is to split your team into a point squad and a rearguard. The squad on point is responsible for eliminating all threats from the front while the rearguard puts the hurt on Infected flanking maneuvers. This tactic is especially effective because your rearguard and team are close enough to you that they can swipe Infected off you before they can deal damage to you.

Cornered: Surprisingly, four Survivors crammed into one corner (or closet) works very well. Deploy two of them in a crouched position doing melee while two more stand behind them and unload their weapons, this tactic will get rid of Infected very effectively. This tactic must be abandoned with haste if a Tank, Spitter, or Charger is present. You can tell if a Tank is coming because there will be cue music, the screen will shake, and the Tank will make distinctive noises, like the other Special Infected.

Team Versus Strategy:

In Versus mode, think as the infected team would think. Like for the infected team, understanding the map and game mechanics greatly helps. Keep in mind that the enemies are human players, and use specific strategies against them.

A major strategy in Versus mode is spawning denial. That is, getting a spot into you or your teammates' line of sight or close proximity, denies your opponents spawning in that location. With good coordination via microphone, a survivor team can keep locations where enemies can spawn for good advantages in check until they get pass, forcing the opponents to either delay their attack or choose an inferior location. It is possible, although risky, to suddenly rush and get a vital location into a Survivor's line of sight before an Infected player at that location has time to react and spawn, ruining the entire ambush plan.

Tricking the enemy also works. A common trick is the Survivor suddenly stops or back away while approaching supposed ambush spots, such as a corner, a one way drop, or a Witch. This can easily trick the enemy team to spawn or attack too early, allowing the team to dispose of them more safely, or rush through while their special attack is still in cooldown.

The Infected
Coordinating Your Attacks: This is by far the most important factor in a Left 4 Dead Versus match. If a Hunter pounces on his own, he will just get killed before he can do any real damage. If a Smoker tries to constrict a Survivor they will just get freed without any real effort, giving the Survivors about 20 seconds while you respawn or recharge and get into position to try again.

The best tactic for coordinating your attacks is to let the Boomer vomit on as many people as he can. Then, have the Hunters pounce from their hiding spots and make the Smoker pull someone away.

If the Boomer vomits on one person, then pounce or constrict the other three who haven't got Boomer bile on them! The one person will be getting attacked by Infected and will not be able to see that other Survivors have a Hunter on them or Smoker constricting them! Also, coordinate your attacks with the Tank. Wait for the Tank to spawn and let him cause havoc. Then pounce or constrict on any Survivors you see lagging behind or running off too fast. If you're a Boomer alongside a Tank, cover some people in Boomer bile and it's pretty much game over. Tanks are hard on their own, but with a horde of Infected slowing the Survivors down, they don't have much chance of escaping.

Spawning: Most of the time during a Versus match, the Infected team will spawn one Smoker, one Boomer and two Hunters. However, sometimes it will spawn an extra Hunter as a replacement for the Smoker or the Boomer, creating a more aggressive group. This seems to happen randomly, but it appears related to which Infected die and which live. For example, if two Hunters and the Smoker live but the Boomer is killed, the Boomer player is more likely to spawn as a Hunter. Also, in very rare circumstances, there have been teams of four Hunters; this group can cause major problems even for the most experienced Survivor teams.

Do your best to learn the places you can climb to, good ambush spots, etc. Look for climbable spots that players can't reach or for strategic walls you can knock down. In general, the Boomer should spawn ahead of the Survivors so he can properly ambush while the Smoker should spawn behind to pull someone back. Hunters should be near the Smoker or the Boomer to take advantage of the chaos that they create. Obviously this is all situational as there will be times that you will want to spawn behind as a Boomer and run in.

Run Away to Respawn: A good tactic for the Infected in Versus is to get the Director to allow you to respawn. When an Infected gets to far behind the Survivors, a message will appear giving the Infected the option of moving closer to the group. By pressing this, you will be in the respawn mode at the Survivors' location. You can now respawn where you choose with your Special Infected's ability recharged. This is a useful trick to use if you are in a bad position or want a faster recharge of your ability such as in the case of the Boomer. This method does not change your health or reset the cooldown of your special attack.

Friendly Fire
"Whose side are you on, kid?"

- Bill

"I don't know who started this shit, 'kay? But let's just stop the friendly fire right now."

- Nick

"OH, EXCUSE ME? EXCUSE ME?!"

- Coach

"Friendly Fire" refers to any incident where a survivor hits another survivor with an attack. Friendly fire does varying amounts of damage depending on the difficulty setting: In general, friendly fire should be avoided whenever possible. On lower difficulties, friendly fire can be acceptable if it is necessary to kill infected (for example, when a teammate is surrounded by Common Infected), as the infected can deal greater damage than the friendly fire will, but on higher difficulties friendly fire should be avoided entirely.
 * Easy — Friendly fire does not inflict damage, but friendly fire incidents will still register and disqualify players from earning the achievement SAFETY FIRST.
 * Normal — Friendly fire inflicts 10 % of the weapon's damage per hit to the Survivors. Except for deliberate attacks on fellow survivors, on this difficulty friendly fire likely will not pose a threat to the Survivors.
 * Advanced — Friendly fire inflicts 30 % of the weapon's damage per hit to the Survivors. Caution should be exercised, as survivors can now do significant damage to teammates accidentally.
 * Expert — Friendly fire inflicts half damage to the Survivors. Avoid friendly fire at all costs. One full blast from any shotgun will instantly incapacitate/kill a teammate!
 * Expert — Friendly fire inflicts half damage to the Survivors. Avoid friendly fire at all costs. One full blast from any shotgun will instantly incapacitate/kill a teammate!

Bots are not programmed to avoid either giving or receiving friendly fire. They will not move or aim around you if you stand between them and an infected, and they will sometimes move into your line of fire. Friendly fire caused by bots will not deal any damage to the Survivors; however, their shots will still cause flinching, which can disrupt the player's aim. Friendly fire will cause damage to bots, however, so make an effort to avoid hitting AI survivors.

Friendly fire's damage will not be affected by range. Note that gunfire passing through Infected or any other surface does not count as friendly fire, but can still detonate ground placed items (such as Gas cans and Propane tanks).

In all difficulties, when being friendly fired upon, the Survivors' screen will shake, they will move slower, and a damage indicator will appear on their screen. This can hinder a teammate's move and aim, and can make them mistake the enemy's position, especially when they are in panic. Even in Easy Difficulty, Survivors shouldn't attack teammates just for fun; this can cause some trouble when done at wrong moment, and will give the others a bad impression.

There's a glitch if you shoot the tip of the players legs or hands, the game will indicate that "(Player) hit (Survivor)" and the survivor will say their friendly fire quote. But would not take damage.

When a Survivor is between you and your target:
 * Attempt to move to the side of the Survivor to get a clear line of sight of your target. Often, it is possible to shoot past a Survivor safely if you simply adjust your position slightly.
 * If you are nervous about bullet spread hitting your teammate, crouch to improve your accuracy.
 * If you cannot move or the Survivor is moving back and forth, hold your fire and ask them to crouch so that you can get a clear line of sight.
 * If they are crouched, warn them that you are firing over them, and then open fire. Otherwise, they might stand up again when you do not expect it.
 * Aim high. Dangerous weapons like the shotguns have a wider area of effect than other weapons thanks to their lack of pinpoint accuracy. Doing this will save your team from potential friendly fire.
 * When using a shotgun, aim wide. Learn the size of the shotgun's cone of fire and aim so just the corner of your buckshot will hit the Infected. This is usually more than enough to kill a Common Infected, and can be a life saver on Expert. Do not attempt this if you feel even slightly unsure. Melee is still king when it comes to getting Infected off teammates.
 * Switch to your Pistol(s). Depending on what your primary weapon is, your pistols can be more accurate, thus lowering the risk of friendly fire. Also, the relatively low damage of the pistol means that even if you happen to shoot a teammate, minimal damage will be taken.
 * If you're slimed and your vision is obscured, be extremely cautious with your gunfire, especially on high difficulties. If you don't know where your teammates are, hold your fire entirely except for shooting infected that get close enough for you confirm that they are infected. A melee weapon is perfect for this scenario.
 * In Left 4 Dead 2, melee weapons (excluding the Chainsaw) are also very useful to avoid friendly fire. They have an inbuilt 90 % damage reduction to teammates — bringing it down to 30 damage each swing — which is further modified by the Difficulty; in Normal difficulty and Versus, this means melee weapons only do 3 damage per hit to Survivors. Melee weapons will also not ignite carried explosives, such as the Gas Cans and Propane Tanks.

Dangerous Weapons
The following weapons have relatively large areas of effect and thus cause friendly fire havoc. On any difficulty, it is imperative that you know what you are shooting at and have the sense not to stand in front of teammates who are shooting. There are cases where entire teams have been defeated due to taking more damage from friendly fire alone than from hordes of the Infected. On Expert, minimizing friendly fire is absolutely necessary to survive as taking even a few rounds from any kind of weapon is enough to take out a huge chunk of your health and possibly incapacitate you. In the worst case, if you are seriously injured, taking even a round or two of friendly fire can kill you outright.


 * Shotguns: Do not open fire unless you are in front of your teammates. Generally, do not even try to "help" your teammates by picking off targets that are attacking them. If you must shoot, try to fire at the enemy by having them at the edge of your crosshair so that your shot will just barely hit them. This alone may be just enough to kill the enemy and save your friend. However, it's best to just switch to the Pistol, which is far more controllable than the shotgun in terms of spread.
 * Molotovs/Gas Can s: Even on easy mode, fire is the single most dangerous weapon to your teammates in the game. On lower difficulties, fire is dangerous because it can damage multiple survivors at once, dealing more total damage than other types of friendly fire that only hit one person. On higher difficulties, fire deals significantly more damage, and can easily incapacitate or kill an entire team if they are slow to react or low on health. Always warn your teammates before setting any fires and make sure they are far from Survivors. Additionally, especially in The Atrium and The Port finales and in Scavenge mode where Gas Cans are collected and may be grouped together, when several fires are burning in the same area simultaneously (e.g. multiple Gas Cans ignited in a single area), the damage caused by those fires is multiplied by the number of fires. Fire is already dangerous; fire dealing 5 times more damage than normal can be deadly even on Normal difficulty, especially if players are incapacitated and cannot get out of the fire.
 * Pipe bombs: This weapon is dangerous for a different reason than the Molotov. The blast radius is small enough that it is trivial to avoid, but can also set off Propane/Oxygen tanks nearby, making the explosion much deadlier. What is downright impossible is to avoid the horde of Infected a badly thrown Pipe bomb will attract without destroying. If needed, throw the Pipe bomb a medium to far distance away, so if you don't eliminate all of the Infected, at least they're far enough away to attack in relative safety.
 * Bile bombs: This weapon can potentially be even more dangerous than Pipe bombs. Despite the fact that it does not do damage, it summons a horde and does not eliminate it like a Pipe bomb, which can be fatal if Survivors are distracted. Use it only when during a horde, panic event, or finale wave and make sure to throw it to a good spot or somewhere far away.
 * Compressed gas cylinders: These come in two varieties, Propane tanks (white, fat and stubby, relatively common) and Oxygen tanks (green, long and slender, rare). Both of these can be thrown and detonated by gunfire to deal massive damage over a wide radius. That's the problem, in fact — it's sometimes difficult to throw them far enough to avoid blasting yourself or your teammates. It is not possible, however to detonate these items while they are being held by teammates, should a stray round connect with them. Bear in mind that depending on what you shoot the gas cylinder with, it may not explode immediately. It will usually lose some gas before exploding unless shot with a shotgun or hunting rifle. Additionally, it should also be noted that these objects are highly vulnerable to all sorts of fire damage as well, and will prematurely detonate on their own if they are placed too close to any open flames. Despite the risks associated with these gas cylinders, they are still very useful for set-piece defense situations such as final stands or holding out against incoming hordes.
 * Grenade Launcher: The weapon can be very deadly to a team in the hands of a rookie player. The grenades do a large amount of damage even from a non-direct hit and players with little experience will tend to shoot randomly during a horde attack or at Infected who are attacking other players. While their intent may be good any rounds that explode close to fellow Survivors will cause massive damage. Fortunately and unfortunately the Grenade Launcher is rare, fortunately because that means there is less of a possibility for it to show up during a level and unfortunately since players are attracted to weapons they have not seen or used much and will therefore be more inclined to take it with them. Communicate with team members and make sure they know to use extra caution with the Grenade Launcher. Self-inflicted friendly fire damage was increased for the PC version on 9th June 2010, making the weapon even more of a hazard to the user.
 * Chainsaw: Although this weapon is classified as a melee weapon, its heavy damage can easily rip a Survivor to shreds if not careful. It is advised not to pick it up in Expert due to its high damage, the noise attracting Common Infected, and limited fuel unless the user knows what they are doing.

Survivor Deaths
If a Survivor dies, they will drop their items and are unable to play for a bit. When the team gets close to a potential Rescue Closet after a minute or two after their death (there are typically several in each level), the dead Survivor(s) will appear with a yellow outline and yelling for the others to get them out.

If multiple Survivors are dead, refrain from opening the closet until everyone is accounted for. This way, you won't have to look for another Rescue Closet, and have backups in case more Survivors die.

Computer Controlled Survivors
Survivor Bots, (colloquially known as "Bots") are Survivors controlled by the AI. Remember these tactics, as they can mean the difference between life or death. Bots are not really good or bad, as they have their strengths and weaknesses. It is a good idea for new players to start out in Single Player to get a good understanding of Bots and to help them play as both Survivors and Infected. Survivor Bots have specific preferences for certain types of guns, and will generally attempt to pick that type if possible. They will also prefer Tier 2 guns to Tier 1 guns, and will attempt to change weapons if in such a situation even if the Tier 2 is not their preferred type. They may also change from their preferred type to a different gun if low on ammo and a replacement preferred gun type or ammo pile is not available.

Here are advantages for both the Infected and the Survivor team. Some pros and cons to Bots are:

Combat

 * Bots actively search for Laser Sights, ammo piles and weapons if they are near them. One should check the weapons of the bots occasionally when passing an area, as you might miss the chance to have a Laser Sight equipped on your weapon.
 * They will point their weapons towards idle Infected. This helps the player spot any that are hiding in bushes and such.
 * With a Laser Sight, one can quickly find and eliminate Infected.
 * If you are incapacitated, the bots will quickly try to get you up. Bots are unaffected by the reset timer if you or another incapacitated Survivor is being attacked by an Infected.
 * Very accurate, often going for headshots when possible.
 * Even with screen inhibitors such as bile or the storm in The Riverbank or Mill Escape, Return to Town and Town Escape, the bots are still extremely accurate.
 * When near alarmed cars, Bots will refrain from attacking, preventing them from accidentally setting the alarm off. Even if they are knocked onto the car itself, the alarm will not trigger.
 * Their stray bullets can't trigger car alarms either due to balancing reasons.
 * Infected players will find it hard to separate a team with Survivor bots.
 * They are never trigger happy and as such, will never waste their ammo when there are no Infected nearby.
 * They will not retaliate back if attacked by the player, compared to human players who might damage you back as a result of friendly fire.
 * One should be careful though, since bots are notorious for running into the players line of fire unintentionally.
 * They do not deal friendly fire damage to the player either. The only way a bot can cause friendly fire is by accidentally setting off a gas can, propane tank, oxygen tank or explosive barrel when equipped with explosive ammo.
 * Bots are capable of killing Witches instantly. However, this often through pure chance such as the bots trying to pass a Witch in a narrow corridor such as outside a safe room.
 * They will teleport themselves to you if you are too far from them, provided that they are not being attacked by the Infected.
 * With human players, bots will try to "mediate" between the group if one player is in the lead while another is behind.
 * Bots can't startle Wandering Witches with gunfire; they can only startle them if they touch her.

Healing

 * Bots won't hesitate to heal you or give you items if you need it.
 * They'll still heal themselves if they or another Survivor is wounded enough to make them use their health kit on them.

Combat

 * Bots often handle Special Infected poorly if they manage to get someone, resulting in unnecessary damage:
 * The Jockey — If a Jockey grabs someone, the bots will typically chase after the Jockey instead of shooting it down. In most cases when a Jockey has grabbed someone, shooting it is the best way to dispose of one, even if friendly fire occurs. They cannot dead-stop Jockeys.
 * The Smoker — Bots are often conflicted with rescuing a Survivor; they may shoot the Smoker, or will try to melee the tongue to free you.
 * The Charger — Bots typically let themselves get rammed by a Charger, failing to dodge it in time unless the player pulls themselves far away for the bots to follow you. If the Charger has grabbed someone, bots typically switch to pistols and will run into melee range to kill the Charger.
 * The Hunter — Bots might try to melee the Hunter off you. They cannot dead-stop Hunters.
 * The Spitter — Bots don't actively avoid the spit puddle until they start taking damage, however they do take reduced damage.
 * The Tank — Bots have a lot of issues with the Tank:
 * Like the Charger and the Spitter, bots don't tend to avoid the Tank's rock throw.
 * Bots might try to get you back up if you are incapacitated, resulting in the Tank running up to them and smashing you instead. This will kill you very quickly on Advanced and Expert.
 * Bot will always shoot the tank during its death animations, essentially wasting their ammo.
 * The Witch — Bots often struggle against Witches.
 * If a Special Infected pins you while a Witch is active, the bots will do nothing to save you until the Witch is killed or flees the area. This is because a startled Witch is the bots' highest priority over everything else.
 * Bots might try to revive you if you are incapacitated from other sources and a Witch is after you, resulting in another incapacitation which can result in death.
 * Aside from the aforementioned, Bots will usually prioritize whoever Survivor was incapacitated or pinned by the Special Infected first despite they will still attempt to save the pinned Survivor by shooting at the pinning Special Infected if on range. This can sometimes lead to unnecessary damage especially when the Survivor they're programmed to save strays too far.
 * This can also cause the Survivor Bot to become vulnerable to nearby Special Infected especially if only one is attempting to save a pinned Survivor.
 * In Left 4 Dead 2, a lone bot usually fares poorly when surrounded by multitudes of Common Infected, making them vulnerable due to the fact that they are not programmed to use melee weapons and the inclusion of melee fatigue.
 * They cannot utilize shortcuts properly. As such, if you get pinned by a Special Infected while utilizing a shortcut where they cannot get to, you will most likely die.
 * In The Sugar Mill, this can lead to bots accidentally startling Witches.
 * Bots cannot utilize throwables, which forces the player to be the only one to use Bile bombs, Pipe bombs and Molotovs.
 * They cannot utilize deployable ammo packs correctly — if an Incendiary ammo pack is deployed and followed up with an Explosive ammo pack, the bots will first grab from the incendiary ammo, then from the explosive ammo, essentially wasting an ammo pack.
 * Bots with submachine guns or assault rifles tend to expend their ammo quickly.
 * Mutations:
 * Hard Eight and Special Delivery — Bots might be overwhelmed by the sheer amount of Special Infected present on the map.
 * Chainsaw Massacre and Four Swordsmen — these mutations will break the AI scripts. Essentially, whenever the bots see any Infected they can reach, they will automatically go for them. This makes Gauntlet Crescendos and Hard Rain's The Sugar Mill very difficult. In the case of the former, bots will stay behind and kill Infected, forcing the player to venture forward alone. In the case of the latter, many Witches will be startled and result in them using their health kits and temporary healing items very quickly.
 * Last Gnome on Earth and Healing Gnome — Bots will not carry the gnome. In case of the former, having only one human player alive is a big disadvantage, because they are the only one that can carry the gnome. In case of the latter, bots' will have no access to any forms of healing, unless the team make it to the safe room.
 * Bots rarely use melee weapons and will usually stick to pistols.
 * This is due to a script issue that limits how many "melee" survivor the team can have (default is set to 1), which means the bots will never use any melees if one other Survivor using one. This can be modified by editing a script to allowing more "melee" survivors in the team.
 * Bots will use melee weapons however if a human players goes idle while using one, they will still swap for a pistol when a chance arises.
 * Lack of communication — Bots can only communicate with simple commands provided by the game, while human players can speak to each other and communicate information between teammates.
 * Player-led — Bots are led by the player(s). They won't go ahead unless something interests them.
 * As a result, if all the player(s) die to the Infected, it results in a restart from the last saferoom, as the bots cannot lead themselves. This can be modified by changing the code to have the bots press on until they rescue the player or reach the saferoom.
 * In Versus, this can result in the Infected players solely targeting the human player(s) only to quickly end their run.
 * Bots are sometimes oblivious to items off the main path and may not pick them up, even if they are pushed near it. Temporary healing items can still be given by using the shove command at them.
 * Bots refuse to pick up M60s, Chainsaws and Grenade Launchers. They can still utilize them though; for the Grenade Launcher, it is only possible if the human player who picked it up goes idle. However, they will eagerly swap the item for other items if given the chance.
 * The only exception with the Chainsaw is the Chainsaw Massacre and Gib Fest mutations. In the former, despite starting with a P220 Pistol, they will pick up a chainsaw due to the nature of the mutation. They are automatically given the M60 on Gib Fest.
 * If the Infected gets close to the bots when they are using Hunting or Sniper Rifles, bots will switch to their pistols, which are typically ineffective against hordes on higher difficulties.
 * A notorious glitch occurs with Ellis where he will stick with the Hunting Rifle even if a Sniper Rifle is nearby, unless a Sniper Rifle spawns before a Hunting Rifle does.
 * Bots stick to the player. As a result, they won't use strategies that you might use with other human players or your own preference.
 * Bots do not grasp the idea of bullet penetration. As a result, they won't fire at walls that bullets can pierce if a Special Infected is hiding behind it and can startle sitting Witches by accident if another Infected is near her when they fire.
 * Bots sometimes allow both Common and Uncommon Infected free hits on them. This typically happens if they are near alarmed cars.
 * Bots will not help collecting or pouring gas cans during scavenge game or finales.

Healing
Bots are programmed to use healing items whenever their health falls below certain thresholds. This typically makes their choices very bad.


 * Health Kits:
 * Bots are relentless in healing wounded players who fall below 40 health. While it is possible to stop them from healing you by taking out your own health kit or temporary healing item, they won't stop until you're healed back up.
 * Bots will use health kits on themselves if they fall below 30 health (40 on Xbox 360) regardless of the state they're in. In most cases, using health kits are only needed if you're about to fall below 30 health (40 on Xbox 360), another health kit is provided for the team, or in the near-death state. Temporary healing items are typically better as they are more common to find.
 * In safe rooms, they will heal themselves if below 75 health. On Expert, this is lowered to 40.
 * Bots won't use health kits if there are too many Infected in the vicinity.
 * They might try to heal you when it is better off running to the safe room or rescue vehicle.
 * In the safe room between The Milltown/The Sugar Mill and Mill Escape/Return to Town (and the health kit cabinet in Town Escape), bots typically grab the health kits on the counter rather than take from the cabinet. This essentially wastes health kits in the cabinets as those are restocked when the team returns.
 * Bots leave a health kit for you to use. If multiple health kits are still available when they use their designated health kit, they will grab those before proceeding.
 * Defibrillators — Bots cannot carry or use defibrillators.
 * Temporary healing items — Bots will use Pain pills or adrenaline shots once they reach 50 or lower health (60 on Xbox 360). They will also give players their pills or adrenaline if they are at such health and are not carrying pills or adrenaline shots on them. An occasional glitch can occur where if given pills or adrenaline shots, bots might prematurely use them.
 * Bots often heal poorly. A notorious example is when a bot uses pain pills upon getting back up, only to use their health kit immediately after consuming the pills.

Medical attention
Whenever possible, try to help fallen comrades up or cover the person helping them up. Remember that the game is very punishing to those who don't stick with their team, and the less Survivors there are, the weaker they are in a group. When in doubt, just remember: when you're facing endless numbers of Infected, having three live people covering your back instead of two live players and one dead teammate can make all the difference. No one can survive the infection alone.

Help a friend up as soon as they fall and the area is clear. Until the area is clear, cover them. It is impossible to help someone up while Infected are attacking you or your fallen comrade. If there's a Tank and he is far away, go ahead and rescue.

It is imperative to understand that if you are facing two incapacitated survivors — one who is simply down not under attack, and one who is under attack (by a hunter pounce, smoker pull, etc.), you should help the attacked Survivor first, especially on higher difficulties.

Once you sustain damage, you can regain health by/with:
 * 1) First aid kit: Stabilizes your health and puts you into the green (80 or better health).
 * 2) Pain pills: Adds 50 temporary health points to your current health. In addition, having at least 40 health will allow a Survivor to run at full speed.
 * 3) Adrenaline: Adds 25 temporary health points, which decay at a slower rate, to your current health. In addition, fatigue does not act against you when shoving, you are not slowed down when hit, and you move much faster.
 * 4) Defibrillator: Revived players respawn with 50 permanent health. Although this is not reliable, it would work if you commit suicide and have a teammate defibrillate you.
 * 5) Rescue Closet: In Campaign mode, dead players eventually return to the game in Rescue Closets. Rescued survivors come back with 50 permanent health, a Tier 1 weapon, and a PP20 Pistol.
 * 6) Level end: When the remaining Survivors finish the campaign, any dead players respawn with 50 permanent HP and a PP20 Pistol.

Being helped up:
 * Restores the helped player to 30 temporary health
 * If a player gets downed 3 times, then on the third time they die. They can come back by a Rescue Closet, a Defibrillator, or having the remaining players finish the level.

'''Death is not permanent. How to return:'''
 * Your teammates will need to advance a certain distance beyond your body into the level.
 * You will need to wait 1 minute, unless when playing in Realism, as you will have to wait for the current Chapter to complete.
 * Your teammates then need to open the closet you will spawn in to complete the "rescue" of a "new" Survivor. It's always best to close said closet after rescue, as on some levels the same closet covers a wider than average length of the game. However, in Versus, Survivors are not allowed to return and will not respawn, apart from the Defibrillator, although this makes the team lose 25 points.
 * In Left 4 Dead 2 you can be revived with a Defibrillator and return to the game in the same spot where you were killed.
 * After completing a level, all dead teammates will respawn with 50% permanent health, and no items (health kits, pain pills, pipe bombs, etc.).
 * In some cases Survivors will return with 100% permanent health, though this only occurs on specific levels.

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