Survival Mode

Survival Mode is a game mode initially released as Downloadable Content from Valve Corporation; the Survival Pack. This game mode throws waves and waves of the Infected at the Survivors until they get fully overwhelmed via every survivor dying or or getting incapacitated. There is no way to win, as instead the goal is to survive as long as you can and set new records.

There are currently forty-one different maps to play on in Survival Mode, thirty lifted almost directly from the campaign mode, along with a formerly Left 4 Dead 1-exclusive map called The Lighthouse that is attributed to a campaign called The Last Stand, which was released as part of the pack.

In almost every Survival map, several areas are cut off to prevent reaching the saferoom or overpowered holdout spots. Such examples include boarded up doors/ladders and restrictive barriers cutting the area off from the rest of the map. The only map that is not affected by this is The Atrium in Left 4 Dead 2.

Left 4 Dead
Each survival match starts with indefinite setup time, allowing you and your team to scour the map for useful items. Teams will find health kits, tier 2 weapons, pipe bombs and molotovs, pills, propane tanks, oxygen tanks, and gas cans scattered around the area. Each Survivor automatically spawns with pills, a health kit and dual pistols.

Setup time ends once the designated radio/button (typically re-using the chapter's radio/button for a Crescendo or Finale Event in the campaign) is used, and will start the timer on top of the screen. A horde will be called as infected start to spawn, and the intensity escalates from there. The AI Hunters gain an area of effect stun on survivors near pounced teammates, twice as long as a Hunter's stun in Versus mode.

Left 4 Dead 2
Survival mode gameplay in Left 4 Dead 2 remains similar to Left 4 Dead 's survival mode, with the difference being the new items and infected.

More items for the survivors such as Adrenaline shots, Bile Bombs, more varied weapons and weapon upgrades, and the addition of Uncommon Infected and more Special Infected results in a different gameplay experience compared to Left 4 Dead. Moreover, the Jockey, alongside the Hunter, gain the area of effect stun on survivors near pinned teammates, which is twice as long as in Versus mode.

There is a variant of Survival Mode, a mutation called Versus Survival. Following both Versus and Survival formulas, the Special Infected are played by a human team and both teams must compete for a better time than their opponent to continue the game until one team fails. This mutation became an official game mode as part of The Last Stand Community Update on September 24, 2020.

Strategy
As always, teamwork and staying together are necessary for survival. Beyond that, survival strategies vary from map to map and from team to team. It is possible to obtain a Gold Medal achievement by utilizing just one area of a map, but some may find it more advantageous to move from time to time in order to get more items, ammo and avoid the Tank. And on certain maps, it can be beneficial to stay in motion and run "laps" around the map to prevent infected from catching up. Difficulty increases with time as supplies dwindle, and surviving often involves fending off multiple Special Infected and at times, multiple Tanks.

As with Versus mode (in Left 4 Dead), the melee fatigue cooldown applies.

It is always best to hole up by gathering as much resources and finding the best spot possible before setting off the Horde. For example, preparing special ammo boxes and placing Gas Cans/Propane Tanks in a secure spot can allow the team to grab it quickly in the event of a Tank attack if they do not have any Molotovs on hand.

Once the horde is alerted, the Director will send groups of Common Infected (Uncommons will appear if they can be found in that level; for example, all Hard Rain survival maps will have Worker Infected). The Director will then start spawning Tanks after 40 seconds. The times the Tanks appear are irregular, and the Director can occasionally send two Tanks at the team in conjunction with Special Infected and a horde.

No Mercy

 * The Generator Room
 * The Gas Station
 * The Hospital
 * The Rooftop

Crash Course

 * The Alleys
 * The Truck Depot

Death Toll

 * The Floodgate
 * The Church
 * The Street
 * The Boat House

Dead Air

 * The Crane
 * The Construction Site
 * The Terminal
 * The Runway

Blood Harvest

 * The Warehouse
 * The Bridge
 * The Farmhouse

The Sacrifice

 * Traincar
 * Port Finale

The Last Stand

 * The Lighthouse

Dead Center

 * Gun Shop
 * Mall Atrium

The Passing

 * Riverbank
 * Underground
 * Port

Dark Carnival

 * Motel
 * Stadium Gate
 * Concert

Swamp Fever

 * Gator Town
 * Shanty Town
 * The Plantation

Hard Rain

 * Burger Tank
 * Sugar Mill
 * Cane Field

The Parish

 * Waterfront
 * Bus Depot
 * Cemetery
 * Float
 * Bridge

No Mercy

 * Generator Room
 * Gas Station
 * Hospital
 * Rooftop

Crash Course

 * Bridge
 * Truck Depot

Death Toll

 * Drains
 * Church
 * Town
 * Boathouse

Dead Air

 * Crane
 * Construction Site
 * Terminal
 * Runway

Blood Harvest

 * Warehouse
 * Bridge
 * Farmhouse

The Sacrifice

 * Traincar
 * Barge
 * Port

Cold Stream

 * Junkyard
 * Waterworks

The Last Stand

 * Junkyard
 * Lighthouse

Achievements
Left 4 Dead

None of the Survival Achievements are present in the Xbox 360 version of the game as the Survival Pack is a free DLC.

Left 4 Dead 2

Tips and Tricks
These tips are for general purpose, not for specific maps.
 * Always stick together; breaking off will make everyone vulnerable and severely weaken them.
 * Try to find everything in the map. Throw Gas cans and Propane tanks in places where they won't be shot by accident, so you have a backup supply of "Molotovs" if you do not have any actual Molotovs, or run out of their supply.
 * Place everything you need in the place you plan to hold out in, so you do not have to leave your area for supplies and risk getting attacked easily.
 * Players playing with Bots will be slightly disadvantaged over a team of players. While they have good accuracy, they often don't work alongside the player, especially whilst Infected swarm them. They cannot use any throwables or defibrillators, and are inefficient with healing items, almost never using their health kits if under attack. They cannot rescue teammates easily and the timer ends upon all human players dying.
 * Try to find melee weapons within the map. They are useful when surrounded by Infected or killing distracted Tanks. Most maps tend to have a couple of melee weapons scattered throughout the area.
 * Defibrillators are extremely useful in case the Infected manage to kill a survivor.
 * Have a Molotov handy to deal with the Tanks, especially when the Director sends two of them to your team. Bile Bombs and Pipe Bombs are also useful for getting Common Infected away from survivors.
 * Tanks and hordes spawn at consistent times during the first 12 minutes.
 * Tanks will consistently spawn at 0:40, 1:55, 2:55, 4:25, 5:25, 5:35, 7:05, 7:45, 8:25, 10:05, 10:45, 11:20, 11:30 and 12:50. Take note of the double Tank spawns at 5:30 and 11:30, as well as the long absence gap of Tanks between 2:55-4:25, 5:35-7:05, 8:25-10:05, and 11:30-12:50.
 * New hordes of common infected do not spawn from approximately 3:50-4:25, 9:00-9:35, and 12:00-12:30; this means that, during those times, the only infected that can spawn are Special Infected, making those times ideal for ammo runs, healing, or other actions that would be risky otherwise.
 * Always try to find a spot where you have an advantage of some sort. Consider the following when choosing a place to hold out:
 * Ammunition: Is there an ammo pile or a weapon pickup nearby that you can use to replenish your ammo without having to wade through hordes of infected?
 * Supplies: Are there any other supplies nearby that you can pick up when you use up the ones you're currently carrying (i.e. pills, First aid kits, etc.)?
 * Points of Entry: Where will the infected come from? Try to keep the number of entry points down to two or one, if possible, so that at least two survivors are covering each entrance. How much warning will you have when they come in that way? Will you be able to kill them before they reach you? This is the most important consideration for when you have to fight Tanks, unless you have an escape plan when the Tank comes.
 * Escape Routes: Is there a specific route you can take that will get you away from the infected quickly, or at least give you room to breathe and kill any major threats? Is there somewhere you can go that will confuse the Infected's AI and force them to take a longer route to reach you, buying you some time?
 * High Ground: Where do the Infected climb up? How fast do they reach you? If you fall, get knocked or dragged off, how long does it take to get back up to your teammates, and how likely can those situations occur? (i.e. is there a handrail keeping you up high, or could any passing Smoker bring you down almost instantly)?
 * Line of Sight: How far away can you start killing infected? How long does it take for an infected to reach you after you first start shooting them? This is an especially important consideration when dealing with Tanks, because if you can see a Tank from far away, you can potentially kill it before it even reaches you.
 * Survival mode has similar mechanics to Versus mode. Jockeys and Hunters can stumble nearby players when they pin a target with double the stumble time of Versus mode, and can leave them open for attack or fall off ledges. However, a Smoker's drag does not cause damage to players.