Jeff was originally a young latent psychopath who brutally beat up a trio bullies, Randy, Keith & Troy, who were picking on him and his brother Liu in the town they had just moved to. Liu took the blame for it and was arrested, sending Jeff into a deep depression. The bullies later attack Jeff again at a party, and Jeff kills one of them, but not before getting covered in bleach and lit on fire by Keith. During this fight, Jeff's mind permanently snapped.
When Jeff woke up, he was at the hospital and his head was wrapped in bandages. When the bandages were taken off, it was revealed that his face had become disfigured and ghastly pale from the burns, with bright red lips and a leathery texture. Jeff said that he liked his face this way and laughed hysterically, but the doctor foolishly thought that this insanity was merely a side effect of the painkillers and let Jeff go home.
Later that night, Jeff's mother finds him carving his face into a permanent smile so that he would no longer have to exert energy to smile, as he put it, and burning off his eyelids so he can always see his face. Jeff's mother went to her husband to tell him that their son had gone completely mad and needed to be killed, but Jeff caught them and stabbed them to death. This woke up Liu (who was recently released), with Jeff telling him as he was about to plunge the knife into his body, "just go to sleep".
Sometime later, an "ominous unknown killer" emerged and went on a killing spree. A boy who was lucky enough to survive the killer's attacks described the man as having inhumanly pale skin, a hideous smile, and dark, constantly open eyes. What Jeff's killing sprees are like after this incident is up for interpretation.
Sesseur VersionOn October 3rd 2008, a YouTuber named "sesseur" uploaded a video called "Jeff the Killer [Original Story]". This video came out before the famous creepypasta was written, and is listed on Know Your Meme as the earliest known mention of Jeff the Killer on the internet.
Sesseur claims he is the one who created Jeff the Killer and that every internet story about Jeff the Killer is fake, including the famous creepypasta. He claims Jeff never had an incident with bullies or bleach. Instead, he claims that Jeff was hauling a gallon of acid into his bathroom to clean out his bathtub but slipped on a bar of soap and the acid splashed all over his face and he was taken to a hospital due to the neighbors hearing his cries.
Another version of the story was added to 4chan, and is shown below.
As a result of brutal bleaching and being set to fire, Jeff is granted with perpetually insipid, pale skin. Having burnt his eyelids off in an attempt to never sleep, so he could always see that "beautiful" face of his, his eyes are lined with ragged black skin, giving him an even more ghostly stature. After the "incident", in the hospital he had found he now withholds thick, black hair - which he lets fall to various shoulder length, - and possibly one of the most distinctive traits of all: the terrifying smile that he had sliced into his face.
Jeff's build is commonly described as slender, reaching a tall height of around six feet. His clothing normally consists of lifeless colors such as white and black, skinny jeans, sweatshirts, and the usual bloodstained t-shirts and converses.
Relation to Slender Man
There are many different ways in which fan content portrays Jeff The Killer and Slender Man in relation to each other.
Mortal Rival of Slender Man
Some fanworks depict Slender Man as mortal enemies on-par with one another's skills. While these are non-canon to both Jeff the Killer and Slender Man mythos', it is nevertheless a popular combination of the two in fanart.
Depictions of Jeff typically show him going into combat with Slender Man using his knives. Most art rarely depicts Jeff as having sustained any serious injuries, while Slender Man may have sustained injuries that would be serious to a human, but do not appear to slow him down. Jeff is not shown using any special "powers" or magical abilities, while Slender Man is typically shown using his tentacles.
According to fanworks (especially fanart), the two appear to be deadlocked in combat, with neither capable of overpowering the other. Images of Jeff defeating Slender Man and vice versa do exist, but are a rarity in contrast to images, videos, and fanfictions regarding the two fighting. Whether one is more powerful than the other is entirely up to individual debate, although most works do tend to remove large numbers of Slender Man's inherent traits (debilitating radiation, teleportation, etc), in favor of a more balanced fight. Additionally most fanworks depict Jeff close, if not directly within striking range, of Slender Man. Whether these works imply superhuman abilities on Jeff's part or not is left up to the viewer.
Jeff is rarely, if ever, depicted as Slender Man's proxy. Fanfiction does exist painting Jeff as some kind of super-proxy that escaped Slender Man's grasp, however the fanworks usually outright state that Jeff is not a proxy and is too insane to be controlled by Slender Man. As a result, since Slender Man cannot control Jeff and cannot turn him into a proxy, he tries to kill him, but finds his opponent is far tougher than he expected.
It is important to note that Jeff and Slender Man exist in their own canon. Neither have interacted in any canonical works, and are entirely separate entities from different universes. The two have only ever clashed in the "Creepypasta World" theory, which stipulates all creepypasta are interconnected tales. Despite not being a creepypasta in and of himself, Slender Man is usually included in this world and does battle with other creepypasta. The Creepypasta World is also non-canon, and has never existed in any canonical works.
An alternate version of Jeff the Killer psychologically influenced by The Slender Man, dubbed The Virus in this series, appears in the webseries Jeff Woods, an installment of the Architect-Verse series.
Jeff the Killer is known for luring his victims to an eternal slumber with a butcher or steak knife and his soft, eerie tone of voice. Even though he prefers to murder his victims with knives, he is more than willing to use any form of weapon when placed in a desperate situation. His blood thirsty attitude ranges from being a drunken jerk who went toe to toe with Slender Man to a child murdering psychopath who takes photos of his mutilated victims and hides them underneath his house.
- When the trailer for Slender: The Arrival was first released, numerous viewers mistook the Chaser for Jeff due to the similarities in their appearance. Like Jeff the Killer, the Chaser wears a white hoodie, black pants, and many people mistook the white mask she wears for Jeff's pale white, smiling face.