History WhatCouldHaveBeen / Left4Dead

** The Witch was originally supposed to attack the entire group if disturbed. However playtesters could not consistently kill her before she downed every member of the team and she would often spawn in a choke point, making the level impossible to finish. This was deemed too hard and she was restricted to killing only one player and then running away, so if the team was willing, the one with the lowest health could, in the worse case scenario, sacrifice themselves for the other three.

* ''Left 4 Dead 2'' was supposed to have an ammo pack, an item that a player could deploy where the team got more ammo. This idea clashed with Valve's idea of "less ammo piles for more guns" and play testers saw the ammo pack as worthless since it replaces the first aid kit and, given how items tend to spawn, would probably most frequently be found [[DepartmentOfRedundancyDepartment next to a regular ammo pile anyway]], so they scrapped the ammo pack concept and replaced with the Incendiary/Explosive packs.

** Nick was originally a convict who had broken out of jail and stolen a white suit. The character concept was scrapped and changed to Nick being a con man in a nice suit. In a strange twist, Nick was the only survivor whose initial model was primarily unchanged throughout development; at most, Nick's suit was originally crisp white, with dirt and grime added shortly before release.
** Rochelle had several design changes to her appearance during development. Originally, she wore an orange shirt and had her hair in a bun. Rochelle's next design changed her shirt to an orange-red color with the Depeche Mode band logo on it and her hair changed to a ponytail. The final design Valve settled on was Rochelle with cornrows and her shirt color changed to pink.

** Ellis' early designs were initially a typical mechanic look - green hat, completely white shirt and light blue overalls. His E3 reveal changed this to orange overalls, a white and blue shirt and his trademark 'blue truck' cap (like the above, this look can be seen on the "Swamp Fever" poster). This was then changed to his beige Bullshifters t-shirt and back to the light blue overalls upon release.

** The Spitter's first design had it in a nightgown which was scrapped because the rendering costs for a physics based clothing was too costly. The next design made it look like a female Boomer in a sense, but was also scrapped. The design after that made the Spitter look like a zombified, pregnant Literature/PippiLongstocking, which Valve quickly scrapped when play testers made pregnancy jokes, until they came up with the final design of the Spitter. The Spitter's spit originally stuck to a survivor that got hit and it would damage them over time, but it was cut out for being overpowered since there was no way to get it off save waiting out the damage. The acid pool from the Spitter also changed colors to reflect its intensity but it was then changed to be just a bright green.

** Initially the Fallen Survivor was cut due to not being thematically tied to any campaign and was basically a mobile gas can (he had Molotovs on him that would trigger if shot). This made any hordes they were in too easy, as killing one would set the entire horde on fire. He was later re-released with The Passing, recycling programming from the Screamer cut from the first game to cause him to run away on spotting a Survivor, but also spawning with droppable supplies such as medkits, pills and grenades.

* [[https://cdn.discordapp.com/attachments/354608543812419596/800539180923879464/77ff3909f7e5ba628b334113dec7c5b5.png A bunch of potential achievements]] for the Last Stand update were cut in development for potentially being ThatOneAchievement, encouraging bad playstyles, or in the case of "Jimmy Gibbed Jr.", modders could circumvent Jimmy Gibbs Jr.'s extreme rarity. In addition, [[https://cdn.discordapp.com/attachments/354608543812419596/800539322310721556/eb640548e1e712368b1190cc80a04b8d.png some of the achievements that were added]] originally had different names before Valve renamed them.

* When a survivor was incapacitated, they had the ability to crawl so they weren't stuck in one place. This idea got axed for allowing survivors to negate any damage done to them by being able to move around and crawl to their teammates for help. Some modded servers have this feature enabled.

** During the No Mercy campaign, Bill was supposed to express paranoia about becoming an infected, but this was reduced to Bill asking his fellow survivors to shoot him should he ever turn.

** The Witch was originally supposed to attack the entire group if disturbed. However playtesters could not consistently kill her before she downed every member of the team and she would often spawn in a choke point, making the level impossible to finish. This was deemed too hard and she was restricted to killing only one player and then running away, so if the team was down the man with the lowest health could, in the worse case scenario, sacrifice himself for the other three.

* ''Left 4 Dead 2'' was supposed to have an ammo pack, an item that a player could deploy where the team got more ammo. This idea clashed with Valve's idea of "less ammo piles for more guns" and play testers saw the ammo pack as worthless since it replaces the first aid kit and, given how items tend to spawn, would probably most be found frequently [[DepartmentOfRedundancyDepartment next to a regular ammo pile anyway]], so they scrapped the ammo pack concept and replaced with the Incendiary/Explosive packs.

* The Infected:
** The Spitter's first design had it in a nightgown which was scrapped because Valve had difficulty trying to render a free flowing piece of clothing. The next design made it look like a female Boomer in a sense, but was also scrapped. The design after that made the Spitter look like a zombified, pregnant Literature/PippiLongstocking, which Valve quickly scrapped when play testers made pregnancy jokes, until they came up with the final design of the Spitter. The Spitter's spit originally stuck to a survivor that got hit and it would damage them over time, but it was cut out for being overpowered since there was no way to get it off save waiting out the damage. The acid pool from the Spitter also changed colors to reflect its intensity but it was then changed to be just a bright green.

** Smokers got the name originally because they would appear in a puff of smoke, abduct a survivor, and disappear. This however proved to be too difficult for players to use and was instead replaced with the tongue as the Smoker's primary attack. His smoke effect also went through several iterations, where it would instead be a secondary attack that pushed people back, There was also a variable for it to causing poison damage (a leftover of this can still be seen in the game, where survivors cough as they go through the smoke) but these were all ultimately cut (the smoke now obscures your view, but does nothing else to you). Another feature was that those being caught by Smokers could also shoot back, freeing themselves. This still remained in the game in a small capacity; you have about 2 seconds after the Smoker starts pulling you in to shoot him, but after that window passes you'll be helpless.

* Valve experimented with a random model system for pistols, where the basic handguns found in maps were planned to randomly choose between a number of different models, effectively averting OnlySixFaces for weapons without compromising gameplay balance. Valve cut the system and the models intended due to the strict memory limits of consoles, and the only remnants of the system still present in the game are the Dual Pistols using two different models (a P220 on its own/in the right hand and a Glock 26 in the left) and their texture name in the data, "v_'''4'''pistols". The modding starter kit on the PC version includes low detail and untextured models of the two additional pistols Valve planned, a Ruger .45 and an M1911 similar to the handgun model in the first game. The item randomizer functionality were eventually fully restored on the PC version through {{GameMod}}s, usually labelled as RNG and for various objects in game.
* Bile Bombs originally were able to splash other players, creating the same effect as being hit by a Boomer's vomit, but this feature got disabled for being too annoying in the heat of a major fight.

** The Hard Rain campaign had some level designs scrapped in the final version. Originally, the Burger Tank was farther away from the start point, which meant players had a ways to go before they could pick up weapons. Players also had to turn on the lights for every house they passed through since by the time they made the return trip, the hurricane made everything dark. Valve moved the Burger Tank closer to the river and they also made the lights from the houses turn on by themselves.
** During the development of The Passing, Valve's original plan was one of the ''Left 4 Dead 1'' survivors would be dead, but the unlucky victim was picked at random for every play through. The idea was hinted further when Valve posted a teaser poster of The Passing on their web site and the old survivors in the background would randomly switch characters among a group of three whenever the viewer reloaded the page or revisit it later. Due to difficulties with contacting Bill's voice actor Jim French, Valve decided to settle with Bill being the dead Survivor.

** Nick was originally a convict who had broken out of jail stole a white suit. The character concept was scrapped and changed to Nick being a con man in a nice suit. In a strange twist, Nick was the only survivor whose initial model was primarily unchanged throughout development (the other 3 had some changes to their looks). Nick's suit was also originally crisp white; dirt and grime were added shortly before release.

** Coach went through several clothing colour iterations but otherwise his model more or less remained the same. Early concept art revealed he sported a white and light blue shirt (along with a gridiron helmet and whistle, though his reveal in the first E3 2009 trailer omitted those), and then opted for an aqua and gold shirt with a puma logo instead. His final design eventually came to be the purple and gold shirt with 'FHS'. Interestingly, the aqua and gold shirt look can still be seen on him in the poster for the "Swamp Fever" campaign. Coach also wore makeshift armor with a football helmet as seen in his early design stages, which makes his "That zombie has armor! I want armor!" line [[HilariousInHindsight funnier than it should be.]] Doubly so with mods that can give Coach's character model actual armor.

** The Spitter's first design had it in a nightgown which was scrapped because Valve had difficulty trying to render a free flowing piece of clothing. The next design made it look like a female Boomer in a sense, but was also scrapped. The design after that made the Spitter look like a zombified, pregnant Literature/PippiLongstocking, which Valve quickly scrapped when play testers made pregnancy jokes, until they came up with the final design of the Spitter. The Spitter's spit originally stuck to a survivor that got hit and it would damage them over time, but it was cut out for being overpowered. The acid pool from the Spitter also changed colors to reflect its intensity but it was then changed to be just a bright green.

** Initially the Fallen Survivor was cut due to not being thematically tied to any campaign and was basically a mobile gas can (he had Molotovs on him that would trigger if shot). This made any hordes they were in too easy, as killing one would set the entire horde on fire. He was later re-released with The Passing with new programming causing him to run away, but also spawning with droppable supplies such as medkits, pills and grenades.

* Valve experimented with a random model system for pistols, where the basic handguns found in maps were planned to randomly choose between a number of different models, effectively averting OnlySixFaces for weapons without compromising gameplay balance. Valve cut the system and the models intended due to the strict memory limits of consoles, and the only remnants of the system still present in the game are the Dual Pistols using two different models (a P220 on its own/in the right hand and a Glock 26 in the left) and their texture name in the data, "v_'''4'''pistols". The modding starter kit on the PC version includes low detail and untextured models of the two additional pistols Valve planned, a Ruger .45 and an M1911 similar to the handgun model in the first game. The models were eventually fully restored on the PC version through {{GameMod}}s.

* All the survivors have lines of dialogue that go unused due to glitches and Valve choosing not to use those lines. Rochelle and Nick notably have very interesting cut dialogue where Nick is a lot more abrasive towards his fellow survivors and Rochelle was a lot more snarky with dry wit added on top of that. These ideas were revisited for The Passing campaign.

** When the Last Stand community update brought back the first game's Common Infected skins for the L4D1 campaigns, its developers also drew some concepts for L4D1 versions of the Spitter, Jockey and Charger. They ran out of time to finalize and model them since it was a late decision, but have stated their hopes of following up on it if allowed to work on another update.

** Versus mode originally allowed players to take control of a Common Infected while they wait to respawn as a special infected, but this was cut due to how weak common infected were in general and would just frustrate players.

* LaserSight[=s=] were planned but got scrapped due to time constraints; some modded servers have the lasers enabled, though solely as a cosmetic feature. Lasers reappeared in [=L4D2=] as a more fully-fleshed-out idea (reducing the accuracy penalty from moving or shooting).

* The Sewers of No Mercy were originally supposed to have the players go through a gas station. The gas pumps in front of the station, as part of a set piece, could be destroyed and blew up spectacularly. However, this often incapacitated the entire team as it was also tied to a crescendo event, and in the confusion the players often shot at the pumps, blowing themselves up. The gas station was as such moved to the side in the area where that crescendo takes place, the button to start it just out of the blast radius if the station is blown up.

*** Nick was originally a convict who had broken out of jail stole a white suit. The character concept was scrapped and changed to Nick being a con man in a nice suit. In a strange twist, Nick was the only survivor whose initial model was primarily unchanged throughout development (the other 3 had some changes to their looks). Nick's suit was also originally crisp white; dirt and grime were added shortly before release.
*** Rochelle had several design changes to her appearance during development. Originally, she wore an orange shirt and had her hair in a bun. Rochelle's next design changed her shirt to an orange-red color with the Depeche Mode band logo on it and her hair changed to a ponytail. The final design Valve settled on was Rochelle with cornrows and her shirt color changed to pink.
*** Coach went through several clothing colour iterations but otherwise his model more or less remained the same. Early concept art revealed he sported a white and light blue shirt (along with a gridiron helmet and whistle, though his reveal in the first E3 2009 trailer omitted those), and then opted for an aqua and gold shirt with a puma logo instead. His final design eventually came to be the purple and gold shirt with 'FHS'. Interestingly, the aqua and gold shirt look can still be seen on him in the poster for the "Swamp Fever" campaign. Coach also wore makeshift armor with a football helmet as seen in his early design stages, which makes his "That zombie has armor! I want armor!" line [[HilariousInHindsight funnier than it should be.]] Doubly so with mods that can give Coach's character model actual armor.
*** Ellis' early designs were initially a typical mechanic look - green hat, completely white shirt and light blue overalls. His E3 reveal changed this to orange overalls, a white and blue shirt and his trademark 'blue truck' cap (like the above, this look can be seen on the "Swamp Fever" poster). This was then changed to his beige Bullshifters t-shirt and back to the light blue overalls upon release.

* Francis and Zoey were originally going to have an interest in each other, but the idea was scrapped due to complaints that it was too distracting.
* Zoey's voice actor during the early stages of the game was slightly different compared to the current voice actor (early Zoey has a somewhat deeper voice compared to the current Zoey voice). The sound files for the original voice actor are still used if Zoey triggers the start of a finale. Zoey's screams when she falls to her death are also from the voice actor in the early stages, but this one was [[ThrowItIn intentionally kept in the game]] because Valve liked how well the screams sounded.
* When the first game was still being developed under Turtle Rock Studios, the survivor designs had a much gritter and survivalist look to the four characters. When Valve took over development of the game, the survivors underwent redesigns to make them stand out from the environment and zombies.
** Francis originally had a full beard, longer hair, and was overweight but dressed similarly to his final version. A remnant of this still exists in the final version of the game, as Louis will still sometimes call Francis fat if he gets shot by him, even though Francis is currently muscular. Concept art for Valve's redesign was basically the same as the final game, but had less facial hair.
** Louis was dressed in a heavy jacket over regular street clothes, and had a bandolier of shotgun shells strapped to his torso. His face was also different with a full beard and short curly hair with a bandage on his forehead. Valve's redesign was virtually unchanged from concept to final game.
** Bill's original model had him in a military combat vest over an olive-drab hoodie along with bulkier pants, but was otherwise similar to his final design. Concept art for Valve's redesign was nearly the same as the final version, but had a striped shirt under his jacket and was clean-shaven instead of bearded.
** Zoey was dressed in a red hoodie with ammo gear, long striped socks, baggy shorts, boots, and kneepads. She also had a completely different face model that resembled [[VideoGame/{{Portal}} Chell]]. Concept art for Valve's redesign was very similar to the final, but had untied hair and a bandana wrapped around her head.
* During the No Mercy campaign, Bill was supposed to express paranoia about becoming an infected, but this was reduced to Bill asking his fellow survivors to shoot him should he ever turn.

* Valve originally planned the game to be restarted from the very first map if all the players died. This was changed to have the survivors restart on the map they died in instead since it was simply too much to lose all that progress from the past 40 minutes. The idea was revisited in ''Left 4 Dead 2'' with the Iron Man mutation mode.

* The helicopter pilot from the No Mercy campaign was supposed to become infected after he rescued you, causing the helicopter to crash and start the events of the next campaign. Playtesters found this concept too depressing since they felt all the fighting the survivors did to get saved [[ShaggyDogStory was a total waste]], so they made each campaign their own story. This idea has been revisited in the sequel where the campaigns are connected to each other, and Valve also retconned the [=L4D1=] campaigns to be connected in the story, in particular with the addition of the "Crash Course" campaign that follows on from the original No Mercy ending.

* Turtle Rock Studios was working on additional downloadable content for ''Left 4 Dead'' that was scrapped due to Valve's focus on ''Left 4 Dead 2''. This included a campaign called "Dam It" meant to tie Dead Air and Blood Harvest together. Two of its interesting aspects were a Panic Event where killing a Smoker or throwing a molotov/pipe bomb inside the fuel storage would trigger an alarm, another being a Crescendo where Survivors had a better chance for survival if they split up in duos; from a nearby fire tower, one pair covers the other two activating the generator to move logs out of the way. The unfinished but playable campaign was [[https://talk.turtlerockstudios.com/t/trss-lost-l4d-campaign/106720 later released to the public]].
* Survivors were able to lock doors to slow down the infected, but the idea got scrapped for making the game too easy for Survivors.
* ''Left 4 Dead 2'' originally had melee weapons break, but it was scrapped for being too annoying. Similarly, the wooden walkways in the Swamp Fever campaign could break and force the survivors to wade through the water, but it was also found to be too annoying and cut.

** Internal development notes released alongside the "original" [=L4D1=] Survivor models reveal that at least a baseball bat, as was preorder-DLC-turned-free-content in the second game, was to be part of the original game.

* LaserSight[=s=] were planned for [=L4D1=] but got scrapped due to time constraints; some modded servers have the lasers enabled, though solely as a cosmetic feature. Lasers reappeared in [=L4D2=] as a more fully-fleshed-out idea (reducing the accuracy penalty from moving or shooting).
* Bile Bombs originally were able to splash other players, creating the same effect as being hit by a Boomer's vomit, but this feature got disabled for, you guessed it, being too annoying in the heat of a major fight.
* VS mode originally allowed players to take control of a Common Infected while they wait to respawn as a special infected, but this was cut due to how weak common infected were in general and would just frustrate players.
* First Aid Kits originally could be passed to another player like pills could, but this was removed since it was just easier to use the kit on a wounded survivor than to give it to them for them to use on themselves.
* When a survivor was incapacitated, they had the ability to crawl so they weren't stuck in one place. This idea got axed for allowing survivors to negate any damage done to them by being able to move around and crawl to their teammates for help. Some modded servers have this feature enabled.
* Smokers and Hunters originally had the ability release their victims to attack a different survivor. The concept was cut out due to it making the Smoker and Hunter too powerful (in this scenario, Smokers and Hunters could incapacitate a survivor and let them go to quickly take down another survivor) and it made getting their achievements too easy. In a similar fashion, Boomers originally had the ability to explode if they fell from a great height, effectively going kamikaze on survivors and splashing them in bile before they could react. AI-controlled Boomers in campaign mode can still do this (usually unintentionally) but this feature is disabled in VS mode for obvious reasons.
** Boomers originally did not have the horde summoning ability and it was essentially [[ActionBomb a walking undead bomb]] whose explosion dealt major damage to anyone that was too close when it popped after being shot. At the same time, another infected, called the Screamer, was being tested where it could not attack survivors but if spotted, it would run away and let out a scream that called a horde. When Valve scrapped the Screamer, it merged the horde calling ability to the Boomer and scrapped the explosive damage idea for it. Traces of the explosive damage can still be seen as the Boomer still destroys doors and windows nearby when it dies, as well as pushing back survivors who are too close in the same manner as if they're standing too close to an explosive prop when it goes up, but the explosion deals no actual damage. The programming for the Screamer running away would later be recycled for the Fallen Survivor Uncommon Infected in the sequel.
** Smokers got the name originally because they would appear in a puff of smoke, abduct a survivor, and disappear. This however proved to be too difficult for players to use and was instead replaced with the tongue as the Smoker's primary attack. His smoke effect also went through several iterations, where it would instead be a secondary attack that pushed people back, There was also a variable for it to causing poison damage (a leftover of this can still be seen in the game, where survivors cough as they go through the smoke) but these were all ultimately cut (the smoke now obscures your view, but does nothing else to you). Another feature was that those being caught by Smokers could also shoot back, freeing themselves. This still remained in the game in a small capacity; you have about 2 seconds after the Smoker starts pulling you in to shoot him, but after that window passes you'll be helpless.
* The Witch was originally supposed to attack the entire group if disturbed. However playtesters could not consistently kill her before she downed every member of the team and she would often spawn in a choke point, making the level impossible to finish. This was deemed too hard and she was restricted to killing only one player and then running away, so if the team was down the man with the lowest health could, in the worse case scenario, sacrifice himself for the other three.
* The Spitter, Jockey, and Charger had several design changes as ''Left 4 Dead 2'' was being developed, but the Jockey and Spitter stand out for several reasons:

* Initially the Fallen Survivor was cut due to not being thematically tied to any campaign and was basically a mobile gas can (he had Molotovs on him that would trigger if shot). This made any hordes they were in too easy, as killing one would set the entire horde on fire. He was later re-released with The Passing with new programming causing him to run away, but also spawning with droppable supplies such as medkits, pills and grenades.
* The Sewers of No Mercy were originally supposed to have the players go through a gas station. The gas pumps in front of the station, as part of a set piece, could be destroyed and blew up spectacularly. However, this often incapacitated the entire team as it was also tied to a crescendo event, and in the confusion the players often shot at the pumps, blowing themselves up. The gas station was as such moved to the side in the area where that crescendo takes place, the button to start it just out of the blast radius if the station is blown up.
* The first map of The Parish campaign for ''Left 4 Dead 2'' was originally supposed to be a lot longer. Instead of the map ending in the convenience store, it would continue on through the park and the bus parking lot. However, the length of the map was simply too long and it was cut down into two maps instead. This unused map can be found in the PC version, as '''c5m1_waterfront_sndscape'''.
* The finale of Dead Center was originally supposed to have the players chase down Jimmy Gibbs to get his car keys. Much like the Screamer above, Gibbs turned out to be too hard to find among the constant-spawning hordes and his higher HP made him hard to kill once found. Gibbs can still spawn during the finale, but as an incredibly rare EasterEgg, while the finale itself was retooled to showcase the new Scavenge mechanic.
* Before ''Left 4 Dead'' started development, Valve worked on a fantasy game involving fairies. It wasn't very good so it was scrapped. Valve thought some sort of co-op game would be better instead which eventually led to ''Left 4 Dead''.
* For the ''Left 4 Dead 2'' survivors, Nick was originally created as a convict who had broken out of jail while still wearing his orange jumpsuit and then stole a white suit later on. The character concept was scrapped and changed to Nick being a con man in a nice suit. In a strange twist, Nick was the only survivor whose initial model was primarily unchanged throughout development (the other 3 had some changes to their looks).
** Nick's suit was originally crisp white; dirt and grime were added shortly before release.
** Rochelle had several design changes to her appearance during development. Originally, she wore an orange shirt and had her hair in a bun. Rochelle's next design changed her shirt to an orange-red color with the Depeche Mode band logo on it and her hair changed to a ponytail. The final design Valve settled on was Rochelle with cornrows and her shirt color changed to pink.
** Coach went through several clothing colour iterations but otherwise his model more or less remained the same. Early concept art revealed he sported a white and light blue shirt (along with a gridiron helmet and whistle, though his reveal in the first E3 2009 trailer omitted those), and then opted for an aqua and gold shirt with a puma logo instead. His final design eventually came to be the purple and gold shirt with 'FHS'. Interestingly, the aqua and gold shirt look can still be seen on him in the poster for the "Swamp Fever" campaign. Coach also wore makeshift armor with a football helmet as seen in his early design stages, which makes his "That zombie has armor! I want armor!" line [[HilariousInHindsight funnier than it should be.]] Doubly so with mods that can give Coach's character model actual armor.
** Ellis' early designs were initially a typical mechanic look - green hat, completely white shirt and light blue overalls. His E3 reveal changed this to orange overalls, a white and blue shirt and his trademark 'blue truck' cap (like the above, this look can be seen on the "Swamp Fever" poster). This was then changed to his beige Bullshifters t-shirt and back to the light blue overalls upon release.
* Several of the levels in ''Left 4 Dead 2'' had some concepts shown in the trailer that are quite different to the final versions of the game. Dark Carnival's coaster level was going to have some sort of wreckage that the survivors had to clear out which would cause an alarm to go off and alert the zombies. The concept changed to the survivors having to activate the ride and run the track to shut the alarm off. Likewise, the finale in The Parish would have the army bombing the bridge as the survivors crossed it, but the idea changed to the army only bombing the bridge after all the survivors reach the helicopter.
** The Hard Rain campaign had some level designs scrapped in the final version. Originally, the Burger Tank was farther away from the start point, which meant players had a ways to go before they could pick up weapons. Players also had to turn on the lights for every house they passed through since by the time they made the return trip, the hurricane made everything dark. Valve moved the Burger Tank closer to the river and they also made the lights from the houses turn on by themselves.

* An Infected called the Leaker was going to be in ''Left 4 Dead 2'' and while no one really got to see what it looked like, the Leaker in the game would plant itself in the ground and then ooze out some sort of acid when the survivors got near. The Leaker got cut due to it being too difficult to use effectively and it was basically doing the same acid attack as the Spitter.
* During the development of The Passing, Valve's original plan was one of the ''Left 4 Dead 1'' survivors would be dead, but the unlucky victim was picked at random for every play through. The idea was hinted further when Valve posted a teaser poster of The Passing on their web site and the old survivors in the background would randomly switch characters among a group of three whenever the viewer reloaded the page or revisit it later. Due to difficulties with contacting Bill's voice actor Jim French, Valve decided to settle with Bill being the dead Survivor.
* There was originally going to be DLC that was based on ''Film/TheCabinInTheWoods'', with both the cabin and [[spoiler:the Facility]]. This can be seen in the film itself, where, in [[spoiler:the Facility]], the four main Special Infected can be seen.
* For the first ''Left 4 Dead'', players in Versus mode had the ability to choose which special infected they could use before spawning in (the Tank was still regulated to the lottery system). The idea was quickly scrapped since players would either play as [[ComplacentGamingSyndrome only one special infected they liked]] or have the whole team use "pinning" infected (Smokers and Hunters) so that they could pin and kill all four survivors at once.
* ''Left 4 Dead'' was originally going to just have the Versus mode, where the Survivor team had to reach the safe house without being killed by the infected players (or get closer to it than the other team) and then the teams switched at the end of the round. Valve had difficulty with keeping the game balanced for both teams and they eventually settled on splitting the game into two modes. Versus mode remained as is, while Campaign mode invariably has players as the Survivors versus AI-controlled Infected.
* Valve experimented with a random model system for pistols in ''Left 4 Dead 2'', where the basic handguns found in maps were planned to randomly choose between a number of different models, effectively averting OnlySixFaces for weapons without compromising gameplay balance. Valve cut the system and the models intended due to the strict memory limits of consoles, and the only remnants of the system still present in the game are the Dual Pistols using two different models (a P220 on its own/in the right hand and a Glock 26 in the left) and their texture name in the data, "v_'''4'''pistols". The modding starter kit on the PC version includes low detail and untextured models of the two additional pistols Valve planned, a Ruger .45 and an M1911 similar to the handgun model in the first game.
* All the survivors have lines of dialogue that go unused due to glitches and Valve choosing not to use those lines. Rochelle and Nick notably have very interesting cut dialogue where Nick is a lot more abrasive towards his fellow survivors and Rochelle was a lot more snarky with dry wit added on top of that. These ideas were revisited for The Passing campaign.
* Valve briefly considered naming the second game "Back 4 More", before settling for a more standard {{Numbered Sequel|s}}.

* For the first ''Left 4 Dead'', players had the ability to choose which special infected they could use before spawning in (the Tank was still regulated to the lottery system). The idea was quickly scrapped since players would either play as only one special infected they liked or had the whole team use "pinning" infected (Smokers and Hunters) so that they could pin and kill all four survivors at once.

* Valve experimented with a random model system for pistols in ''Left 4 Dead 2'', where the basic handguns found in maps were planned to randomly choose between a number of different models, effectively averting OnlySixFaces for weapons without compromising gameplay balance. Valve cut the system and the models intended due to the strict memory limits of consoles, and the only remnants of the system still present in the game are the Dual Pistols using two different models and their texture name in the data, "v_'''4'''pistols". The modding starter kit on the PC version includes low detail and untextured models of the two additional pistols Valve planned: A Ruger .45 and a M1911 similar to the handgun model in the first game.
* All the survivors have lines of dialogue that go unused due to glitches and Valve choosing not to use those lines. Rochelle and Nick notably have very interesting cut dialogue where Nick is a lot more abrasive towards his fellow survivors and Rochelle was a lot more snarky with dry wit added on top of that. These ideas were revisited for The Passing campaign.

* Valve experimented with a random model system for pistols in ''Left 4 Dead 2'', where the basic handguns found in maps were planned to randomly choose between a number of different models, effectively averting OnlySixFaces for weapons without compromising gameplay balance. Valve cut the system and the models intended due to the strict memory limits of consoles, and the only remnants of the system still present in the game are the Dual Pistols using two different models and their texture name in the data, "v_'''4'''pistols". The modding starter kit on the PC version includes low detail and untextured models of the two additional pistols Valve planned: A Ruger .45 and a M1911 similar to the handgun model in the first game.

* Turtle Rock Studios was working on additional downloadable content for ''Left 4 Dead'' that was scrapped due to Valve's focus on ''Left 4 Dead 2''. This included a campaign called "Dam It" meant to tie Dead Air and Blood Harvest together. Two of its interesting aspects were a Panic Event where killing a Smoker or molotov/pipe bomb inside the fuel storage would trigger an alarm, the other being a Crescendo where Survivors had a better chance for survival if they split up in duos; from a nearby fire tower, one pair covers the other two activating the generator to move logs out of the way. The unfinished but playable campaign was [[https://talk.turtlerockstudios.com/t/trss-lost-l4d-campaign/106720 later released to the public]].

** At one point Riot Shields and a Didgeridoo were to be available as melee weapons, but were cut for an unknown reason. The Riot Shield is fully modeled in the game and can be spawned with console commands, but the Didgeridoo only has a low poly model.

* VS mode originally allowed players to take control of a common infected while they wait to respawn as a special infected, but this was cut due to how weak common infected were in general and would just frustrate players.

* Smokers and Hunters originally had the ability let go of their victims to attack a different survivor. The concept was cut out due to it making the Smoker and Hunter too powerful (in this scenario, Smokers and Hunters could incapacitate a survivor and let them go to quickly take down another survivor) and it made getting their achievements too easy. In a similar fashion, Boomers originally had the ability to explode if they fell from a great height, effectively going kamikaze on survivors and splashing them in bile before they could react. AI-controlled Boomers in campaign mode can still do this (usually unintentionally) but this feature is disabled in VS mode for obvious reasons.

** The Spitter's first design had it in a nightgown which was scrapped because Valve had difficulty trying to render a free flowing piece of clothing. The next design made it look like a female Boomer in a sense, but was also scrapped. The design after that made the Spitter look like a zombified, pregnant Literature/PippiLongstocking, which Valve quickly scrapped when play testers made pregnancy jokes, until they came up with the final design of the Spitter. The Spitter's spit originally stuck to a survivor that got hit and it would damage them over time, but it was cut out for being too overpowered. The acid pool from the Spitter also changed colors to reflect its intensity but it was then changed to be just a bright green.

* The first map of The Parish campaign for ''Left 4 Dead 2'' was originally supposed to be a lot longer. Instead of the map ending in the convenience store, it would continue on through the park and the bus parking lot. However, the length of the map was simply too long and it was cut down into two maps instead. You can actually access this unused map on the PC version by entering "map c5m1_waterfront_sndscape" in the console.
* The finale of Dead Center was originally suppose to have the players chase down Jimmy Gibbs to get his car keys. Much like the screamer above, Gibbs turned out to be too hard to find among the constant-spawning hordes and his higher HP made him hard to kill once found. Gibbs can still spawn during the finale, but as an incredibly rare EasterEgg, while the finale itself was retooled to showcase the new Scavenge mechanic.

* An infected called the Leaker was going to be in ''Left 4 Dead 2'' and while no one really got to see what it looked like, the Leaker in the game would plant itself in the ground and then ooze out some sort of acid when the survivors got near. The Leaker got cut due to it being too difficult to use effectively and it was basically doing the same acid attack as the Spitter.
* During the development of The Passing campaign, Valve's original plan was one of the ''Left 4 Dead 1'' survivors would be dead, but the unlucky victim was picked at random for every play through. The idea was hinted further when Valve posted a teaser poster of The Passing on their web site and the old survivors in the background would randomly switch characters among a group of three whenever the viewer reloaded the page or revisit it later. Due to difficulties with contacting Bill's voice actor Jim French, Valve decided to settle with Bill being the dead Survivor.

* ''Left 4 Dead 2'' was supposed to have an ammo pack, an item that a player could deploy where the team got more ammo. This idea clashed with Valve's idea of "less ammo piles for more guns" and play testers saw the ammo pack as worthless since it replaces the first aid kit, so they scrapped the ammo pack concept and replaced with the Incendiary/Explosive packs.

* Laser sights were planned for [=L4D1=] but got scrapped due to time constraints, but some modded servers have the lasers enabled. Lasers reappeared in [=L4D2=].

** Smokers got the name originally because they would appear in a puff of smoke, abduct a survivor, and disappear. This however proved to be too difficult for players to use and was instead replaced with the tongue as the Smoker's primary attack. His smoke effect also went through several iterations, where it would instead be a secondary attack that pushed people back, There was also a variable for it to causing poison damage (leftover of this can still be seen in the game, where survivors cough as they go through the smoke) but these were all ultimately cut (the smoke now obscures your view, but does nothing else to you). Another feature was that those being caught by Smokers could also shoot back, freeing themselves. This still remained in the game in a small capacity; you have about 2 seconds after the Smoker starts pulling you in to shoot him, but after that window passes you'll be helpless.

* The Riot Shield in ''Left 4 Dead 2'' was a melee weapon players could use, but Valve removed the spawn script for it so it would never appear. Mods can enable the weapon to be usable again.

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