4chan is an English-language imageboard website. Users generally post anonymously, with the most recent posts appearing above the rest. 4chan is split into various boards with their own specific content and guidelines. Registration is not possible (except for staff).

Launched on October 1, 2003, the site was modeled on Japanese imageboards, particularly Futaba Channel. 4chan's first boards were originally primarily used for posting pictures and discussing manga and anime. The site quickly became popular, expanded, and now features boards dedicated to a wide variety of topics, from anime/manga to video games, music, literature, fitness, politics, and sports.

The site has been linked to Internet subcultures and activism groups, such as Anonymous, the alt-right and Project Chanology.^[4][5] 4chan users have been responsible for the formation or promotion of Internet memes such as lolcats, Rickrolling, "Chocolate Rain", Pedobear, and many others. The site's "Random" board, also known as "/b/", was the first board to be created, and is the one that receives the most traffic.^[6][7] The Random board has minimal rules on posted content. The site's anonymous community and culture have often provoked media attention.

4chan users have been instrumental in pranks such as hijacking Internet destinations to cause images of Rick Astley to appear in place of their content, coordinating attacks against other websites and Internet users, exposing animal abuse, and posting threats of violence in order to elicit individual and public reactions. The Guardian once summarized the 4chan community as "lunatic, juvenile ... brilliant, ridiculous and alarming".^[8]

The activity of 4chan takes place on message boards and imageboards.^[9][10] The website is split into six categories: Japanese culture, Interests, Creative, Adult (18+), Other, and Misc (18+). These provide for on-topic boards to discuss anime, manga, technology, sport, photography, music, hentai, torrents, travel, physical fitness, as well as a random board. 4chan originally hosted discussion boards on a separate domain called "world4ch", but these were later moved to the dis.4chan.org subdomain.^[11] The site has had at least one employee, a programmer whom 4chan's founder Christopher Poole met via online Tetris. All other moderators are volunteers.^[12] As of 2011, the /b/ (Random), /v/ (Video games), /a/ (Anime and Manga), and /s/ (explicit images) boards were respectively the site's first, second, third, and fourth most popular boards.^[1]

4chan is one of the Internet's most trafficked imageboards, according to the Los Angeles Times.^[13] 4chan's Alexa rank is generally around 700,^[14] though it has been as high as number 56 at times.^[15] It is provided to its users free of charge and consumes a large amount of bandwidth; as a result, its financing has often been problematic. Poole acknowledges that donations alone cannot keep the site online, so he has turned to advertising to help make ends meet.^[16] However, the explicit content hosted on 4chan has deterred businesses who do not want to be associated with the site's content.^[17] In January 2009, Poole signed a new deal with an advertising company; in February 2009, he was $20,000 in debt, and the site was continuing to lose money.^[18] The 4chan servers were moved from Texas to California in August 2008, which upgraded the maximum bandwidth throughput of 4chan from 100Mbit/s to 1Gbit/s.^[19]

Unlike most web forums, 4chan does not have a registration system, allowing users to post anonymously.^[20][21] Any nickname may be used when posting, even one that has been previously adopted, such as "Anonymous" or "moot".^[22] In place of registration, 4chan has provided tripcodes as an optional form of authenticating a poster's identity.^[23] As making a post without filling in the "Name" field causes posts to be attributed to "Anonymous", general understanding on 4chan holds that Anonymous is not a single person but a collective (hive) of users.^[24] Moderators generally post without a name even when performing sysop actions. A "capcode" may be used to attribute the post to "Anonymous ## Mod", although moderators often post without the capcode.^[25] In a 2011 interview on Nico Nico Douga, Poole explained that there are approximately 20 volunteer moderators active on 4chan.^[1] 4chan also has a junior moderation team, called "janitors", who may delete posts or images and suggest that the normal moderation team ban a user, but who cannot post with a capcode. Revealing oneself as a janitor is grounds for immediate dismissal.^[26]

4chan has been the target of occasional denial of service attacks. For instance, on December 28, 2010, 4chan and other websites went down due to such an attack, following which Poole said on his blog, "We now join the ranks of MasterCard, Visa, PayPal, et al.—an exclusive club!"^[27]

4chan was started in 2003 in the bedroom of Christopher Poole, a then-15-year-old student from New York City whose 4chan handle is "moot".^[12] Prior to starting 4chan, Poole had been a regular participant on the Something Awful forums.^[20] He intended 4chan to be an American counterpart to the popular Japanese Futaba Channel ("2chan") imageboard and a place to discuss manga and anime.^[10][28] Upon the creation of 4chan, Poole encouraged users from the Something Awful subforum titled "Anime Death Tentacle Rape Whorehouse", who also happened to be dissatisfied with the forum, to discuss anime on his website.^[29] Poole originally used the Futaba Channel to obtain anime-related images, and liked the concept of a message board where people anonymously shared images, which eventually led to his idea of creating a similar English-based website. During the creation of 4chan, he obtained the source code for the Futaba Channel website, and translated the Japanese text into English using AltaVista's Babel Fish online translator.^[1][30] During 4chan's earliest days, it had only two boards: "/a/ – Anime/General" and "/b/ – Anime/Random" (the very first board to be created); more boards were created over time, and /b/ was eventually renamed to simply "/b/ – Random".^[1][30]

During the early days of 4chan, the boards that originally existed were the anime, random, cute, hentai, and yaoi boards; a lolicon board also existed at /l/,^[32] but after being disabled for a week around the turn of the year 2004 it was removed in October 2004.^[33] The /g/ board also was initially dedicated to guro, before it was deleted and later remade as the "technology" board.^[34] During 2004, 4chan briefly went offline,^[35] then returned fully online a few months later.^[36] Following 4chan's return, some non-anime related boards, such as the weapons, automobile, and video games boards, were introduced.^[37] In 2008, nine new boards were created, including the sports board at /sp/, the fashion board at /fa/ and the "Japan/General" (the name later changed to "Otaku culture") board at /jp/.^[38]

In January 2011, Poole announced the deletion of the /r9k/ ("ROBOT9000") and /new/ (News) boards, saying that /new/ had become devoted to racist discussions, and /r9k/ no longer served its original purpose of being a test implementation of xkcd's ROBOT9000 script.^[39] During the same year, the /soc/ board was created in an effort to reduce the number of socialization threads on /b/. /r9k/ was restored on October 23, 2011, along with /hc/ ("Hardcore", previously deleted), /pol/ (a rebranding of /new/) and the new /diy/ board, in addition to an apology by Poole where he recalls how he criticized the deletion of Encyclopedia Dramatica and realized that he had done the same.^[40]

In 2010, 4chan had implemented reCAPTCHA in an effort to thwart spam arising from JavaScript worms. By November 2011, 4chan made the transition to utilizing Cloudflare following a series of distributed denial of service attacks. The 4chan imageboards were rewritten in valid HTML5/CSS3 in May 2012 in an effort to improve client-side performance.^[19] On September 28, 2012, 4chan introduced a "4chan pass"^[41] that, when purchased, "allows users to bypass typing a reCAPTCHA verification when posting and reporting posts on the 4chan image boards"; the money raised from the passes will go towards supporting the site.^[42]

On January 21, 2015, Poole stepped down as the site's administrator citing stress from controversies such as Gamergate as the reason for his departure.^[43][44][45] On September 21, 2015, Poole announced that Hiroyuki Nishimura had purchased from him the ownership rights to 4chan, without disclosing the terms of the acquisition.^[29][46][47] Nishimura was the former administrator of 2channel between 1999 and 2014, the website forming the basis for anonymous posting culture which influenced later websites such as Futaba Channel and 4chan;^[48] Nishimura lost the rights for 2channel to ex-US Army officer^[49] Jim Watkins^[50][51] following financial difficulties^[52] and a series of scandals involving Nishimura's alleged data mining and sales of 2channel personal user data to political parties.^[49][53]

In October 2016, it was reported that the site was facing financial difficulties that could lead to its closure or radical changes.^[54] In a post titled "Winter is Coming", Hiroyuki Nishimura said, "We had tried to keep 4chan as is. But I failed. I am sincerely sorry", citing server costs, infrastructure costs, and network fees.^[55]

On November 17, 2018, it was announced that the site would be split into two, with the work-safe boards moved to a new domain, 4channel.org, while the NSFW boards would remain on the 4chan.org domain. In a series of posts on the topic, Nishimura explained that the split was due to 4chan being blacklisted by most advertising companies, and that the new 4channel domain would allow for the site to receive advertisements by mainstream ad providers.^[56]

Poole kept his real-life identity hidden until it was revealed on July 9, 2008, in The Wall Street Journal. Before that time he had used the alias "moot".^[12]

In April 2009, Poole was voted the world's most influential person of 2008 by an open Internet poll conducted by Time magazine.^[57] The results were questioned even before the poll completed, as automated voting programs and manual ballot stuffing were used to influence the vote.^[58][59][60] 4chan's interference with the vote seemed increasingly likely, when it was found that reading the first letter of the first 21 candidates in the poll spelled out a phrase containing two 4chan memes: "mARBLECAKE. ALSO, THE GAME."^[61]

On September 12, 2009, Poole gave a talk on why 4chan has a reputation as a "Meme Factory" at the Paraflows Symposium in Vienna, Austria, which was part of the Paraflows 09 festival, themed Urban Hacking. In this talk, Poole mainly attributed this to the anonymous system, and to the lack of data retention on the site ("The site has no memory.").^[62][63]

In April 2010, Poole gave evidence in the trial United States of America v. David Kernell as a government witness.^[64] As a witness, he explained the terminology used on 4chan to the prosecutor, ranging from "OP" to "lurker". He also explained to the court the nature of the data given to the FBI as part of the search warrant, including how users can be uniquely identified from site audit logs.^[65]

4chan has been labeled as the starting point of the Anonymous meme by The Baltimore City Paper,^[15] due to the norm of posts signed with the "Anonymous" moniker. The National Post's David George-Cosh said it has been "widely reported" that Anonymous is associated with 4chan and 711chan, as well as numerous Internet Relay Chat (IRC) channels.^[66]

Through its association with Anonymous, 4chan has become associated with Project Chanology, a worldwide protest against the Church of Scientology held by members of Anonymous. On January 15, 2008, a 4chan user posted to /b/, suggesting participants "do something big" against the Church of Scientology's website. This message resulted in the Church receiving threatening phone calls. It quickly grew into a large real-world protest. Unlike previous Anonymous attacks, this action was characterized by 4chan memes including rickrolls and Guy Fawkes masks. The raid drew criticism from some 4chan users who felt it would bring the site undesirable attention.^[15]

As of May 2017, 4chan hosts 71 imageboards, two of which are hidden, as well as one upload-only Flash board.^[67]

/pol/ ("Politically Incorrect") is 4chan's political discussion board. A stickied thread on its front page states that the board's intended purpose is "discussion of news, world events, political issues, and other related topics."^[68] /pol/ was created in October 2011 as a rebranding of 4chan's news board, /new/,^[40] which was deleted that January for a high volume of racist discussion.^[39]

Media sources have characterized /pol/ as predominantly racist and sexist, with many of its posts taking an explicitly neo-Nazi bent.^{[4][69][70][71]} The Southern Poverty Law Center regards /pol/'s rhetorical style as widely emulated by white supremacist websites such as The Daily Stormer; the Stormer's editor, Andrew Anglin, concurred.^[69]

/pol/ was where screenshots of Trayvon Martin's hacked social media accounts were initially posted.^[72][73] The board's users have started antifeminist, homophobic, transphobic, and anti-Arab Twitter campaigns.^{[70][74][75][76]}

Many /pol/ users favored Donald Trump during his 2016 United States presidential campaign. Both Trump and his son, Donald Trump Jr., appeared to acknowledge the support by tweeting /pol/-associated memes. Upon his successful election, a /pol/ moderator embedded a pro-Trump video at the top of all of the board's pages.^{[77][78][79][80]}

The "random" board, /b/, follows the design of Futaba Channel's Nijiura board. It was the first board created, and is by far 4chan's most popular board, with 30% of site traffic.^[81][82] Gawker's Nick Douglas summarized /b/ as a board where "people try to shock, entertain, and coax free porn from each other."^[9] /b/ has a "no rules" policy, except for bans on certain illegal content, such as child pornography, invasions of other websites (posting floods of disruptive content), and under-18 viewing, all of which are inherited from site-wide rules. The "no invasions" rule was added in late 2006, after /b/ users spent most of the summer "invading" Habbo Hotel. The "no rules" policy also applies to actions of administrators and moderators, which means that users may be banned at any time, for any reason, including no reason at all.^[83] Due partially to its anonymous nature, board moderation is not always successful—indeed, the site's anti-child pornography rule is a subject of jokes on /b/.^[15] Christopher Poole told The New York Times, in a discussion on the moderation of /b/, that "the power lies in the community to dictate its own standards" and that site staff simply provided a framework.^[84]

The humor of /b/'s many users, who refer to themselves as "/b/tards",^[84][85] is often incomprehensible to newcomers and outsiders, and is characterized by intricate inside jokes and dark comedy.^[85] Users often refer to each other, and much of the outside world, as fags.^[15] They are often referred to by outsiders as trolls, who regularly act with the intention of "doing it for the lulz", a corruption of "LOL" used to denote amusement at another's expense.^[84][86] The New York Observer has described posters as "immature pranksters whose bad behavior is encouraged by the site's total anonymity and the absence of an archive".^[87] Douglas said of the board, "reading /b/ will melt your brain", and cited Encyclopedia Dramatica's definition of /b/ as "the asshole of the Internets [sic]".^[9] Mattathias Schwartz of The New York Times likened /b/ to "a high-school bathroom stall, or an obscene telephone party line",^[84] while Baltimore City Paper wrote that "in the high school of the Internet, /b/ is the kid with a collection of butterfly knives and a locker full of porn."^[15] Wired describes /b/ as "notorious".^[85]

Each post is assigned a post number. Certain post numbers are sought after with a large amount of posting taking place to "GET" them. A "GET" occurs when a post's number ends in a special number, such as 12345678, 22222222, or every millionth post.^[88] A sign of 4chan's scaling, according to Poole, was when GETs lost meaning due to the high post rate resulting in a GET occurring every few weeks. He estimated /b/'s post rate in July 2008 to be 150,000–200,000 posts per day.^[89]

Many Internet memes—catchphrases or images that spread quickly, peer to peer, across the Internet^[90]—have originated on 4chan, usually /b/, as its fast moving, crowd psychology nature enables content to quickly be passed on to large numbers of viewers. Other memes originating on the site have gained media attention of a lesser degree. These include "So I herd u liek mudkipz" [sic], which involves a phrase based on Pokémon and which generated numerous YouTube tribute videos,^[20] and the term "an hero" [sic] as a synonym for suicide, after a misspelling in the Myspace online memorial of seventh grader Mitchell Henderson.^[91] 4chan and other websites, such as the satirical Encyclopedia Dramatica, have also contributed to the development of significant amounts of leetspeak.^[92] Adult fans of My Little Pony: Friendship Is Magic are also known to frequent 4chan, having had a board dedicated to their interest.^{[93][94][95][96][97]}

A lolcat is an image combining a photograph of a cat with text intended to contribute humour. The text is often idiosyncratic and grammatically incorrect. In 2005, the meme was widely popularized by 4chan in the form of "Caturday". Every Saturday, users posted pictures of cats with image macros relating to that day's theme.^[98][99]

In 2005, a meme known as the "duckroll" began, after Poole used a word filter to change "egg" to "duck" across 4chan. Thus, words such as "eggroll" were changed to "duckroll". This led to a bait-and-switch in which external links disguised as relevant to a discussion instead led to a picture of a duck on wheels.^[100]

An unidentified 4chan user applied the concept of the duckroll to a 2007 post relating to the video game Grand Theft Auto IV. In March of that year, the game's trailer had been released, and the game's immense popularity caused publisher Rockstar Games' website to crash. The user posted a YouTube link that purportedly led to the trailer, but in reality directed users to the music video for Rick Astley's 1987 song "Never Gonna Give You Up". Thus, the "rickroll" was born.^[100] In an interview with the Los Angeles Times, Astley said he found the meme "bizarre and funny".^{[8][100][101]}

A link to the YouTube video of Tay Zonday's song "Chocolate Rain" was posted on /b/ on July 11, 2007.^[102] The Age reported that 4chan posters urged each other to "swarm" the video on YouTube and thus increase its ranking.^[103] The video became an immensely popular Internet meme, resulting in cover versions by John Mayer and Green Day drummer Tré Cool.^[104] The portion of the song in which Zonday turns away from the microphone, with a caption stating "I move away from the mic to breathe in", became an oft-repeated meme on 4chan and inspired remixes.^[102][105]

The character of Boxxy is portrayed by Catherine "Catie" Wayne, an American Internet celebrity known for her highly energetic vlogs.^{[106][107][108][109]} Her rise to exposure began in late 2008 and early 2009, surrounding self-made videos that were initially made to be posted to her Gaia Online profile.^{[106][107][108][109]} They then spread to 4chan and other sites, resulting in a large online following.^[106]

In his American incarnation, Pedobear is an anthropomorphic bear child predator that is often used within the community to mock contributors showing a sexual interest in children.^[110] Pedobear is one of the most popular memes on non-English imageboards, and has gained recognition across Europe. In February 2010, a photoshopped version of Pedobear appeared along with mascots of the 2010 Winter Olympics in an article on the games in Gazeta Olsztyńska, a Polish newspaper. This was done accidentally; due to the image being used from Google Images, the authors were unaware of the joke.^[111] Similarly, the Dutch television guide Avrobode^[112] used one of the images. It has been used as a symbol of pedophilia by Maltese graffiti vandals prior to a papal visit.^[113]

On February 15, 2009, a user uploaded two YouTube videos that showed the physical abuse of a domestic cat named Dusty by a person calling himself "Timmy". The 4chan community was able to track down the originator of the videos, a fourteen-year-old from Lawton, Oklahoma, and passed his details to his local police department. As a result of this, a suspect was arrested and the cat was treated by a veterinarian and taken to a safe place.^[114][115]

On July 30, 2014, an anonymous user made a reply in a thread on the board /pol/ "Politically Incorrect" of 4chan, criticizing modern art in an ironic fashion, saying:

Less than an hour later the post was photographed off the screen and framed by another user who posted another reply in the thread with a photo of the framed quote. Later the user, after endorsement by other anonymous users in the thread, created an auction on eBay for the framed photo which quickly rose to high prices, culminating in a price of $90,900.00.^{[117][118][119][120]}

A report of Jeffrey Epstein's death was posted on /pol/ around 40 minutes before ABC News broke the news. The unidentified person who made the posts may have been a first responder, in violation of privacy law. The posts are under review.^[121][122]

According to The Washington Post, "the site's users have managed to pull off some of the highest-profile collective actions in the history of the Internet."^[123]

Users of 4chan and other websites "raided" Hal Turner by launching DDoS attacks and prank calling his phone-in radio show during December 2006 and January 2007. The attacks caused Turner's website to go offline. This cost thousands of dollars of bandwidth bills according to Turner. In response, Turner sued 4chan, 7chan, and other websites; however, he lost his plea for an injunction and failed to receive letters from the court.^[124]

KTTV Fox 11 aired a report on Anonymous, calling them a group of "hackers on steroids", "domestic terrorists", and collectively an "Internet hate machine" on July 26, 2007.^[125] Slashdot founder Rob Malda posted a comment made by another Slashdot user, Miang, stating that the story focused mainly on users of "4chan, 7chan and 420chan". Miang claimed that the report "seems to confuse /b/ raids and motivational poster templates with a genuine threat to the American public", arguing that the "unrelated" footage of a van exploding shown in the report was to "equate anonymous posting with domestic terror".^[126]

On July 10, 2008, the swastika CJK unicode character (卐) appeared at the top of Google's Hot Trends list—a tally of the most used search terms in the United States—for several hours. It was later reported that the HTML numeric character reference for the symbol had been posted on /b/, with a request to perform a Google search for the string. A multitude of /b/ visitors followed the order and pushed the symbol to the top of the chart, though Google later removed the result.^[13]

Later that year, the private Yahoo! Mail account of Sarah Palin, Republican vice presidential candidate in the 2008 United States presidential election, was hacked by a 4chan user. The hacker posted the account's password on /b/, and screenshots from within the account to WikiLeaks.^[127] A /b/ user then logged in and changed the password, posting a screenshot of him sending an email to a friend of Palin's informing her of the new password on the /b/ thread. However, he forgot to blank out the password in the screenshot.^[128] A multitude of /b/ users attempted to log in with the new password, and the account was automatically locked out by Yahoo!. The incident was criticized by some /b/ users, in that most reports on the hack focused on 4chan, rather than Palin's violation of campaign law. One user commented, "seriously, /b/. We could have changed history and failed, epically."^[129] The FBI and Secret Service began investigating the incident shortly after its occurrence. On September 20 it was revealed they were questioning David Kernell, the son of Democratic Tennessee State Representative Mike Kernell.^[130]

The stock price of Apple Inc. fell significantly in October 2008 after a hoax story was submitted to CNN's user-generated news site iReport.com claiming that company CEO Steve Jobs had suffered a major heart attack. The source of the story was traced back to 4chan.^[131][132]

In May 2009, members of the site attacked YouTube, posting pornographic videos on the site.^[133] A 4chan member acknowledged being part of the attack, telling BBC News that it was in response to YouTube "deleting music".^[134] In January 2010, members of the site attacked YouTube again in response to the suspension of YouTube user lukeywes1234 for failing to meet the minimum age requirement of thirteen.^[135] The videos uploaded by the user had apparently become popular with 4chan members, who subsequently became angered after the account was suspended and called for a new wave of pornographic videos to be uploaded to YouTube on January 6, 2010.^[135] Later the same year, 4chan made numerous disruptive pranks directed at singer Justin Bieber.^[136]

In September 2010, in retaliation against the Bollywood film industry's hiring of Aiplex Software to launch cyberattacks against The Pirate Bay, Anonymous members, recruited through posts on 4chan boards, subsequently initiated their own attacks, dubbed Operation Payback, targeting the website of the Motion Picture Association of America and the Recording Industry Association of America.^{[137][138][139]} The targeted websites usually went offline for a short period of time due to the attacks, before recovering.

The website of the UK law firm ACS:Law, which was associated with an anti-piracy client, was affected by the cyber-attack.^[140] In retaliation for the initial attacks being called only a minor nuisance, Anonymous launched more attacks, bringing the site down yet again. After coming back up, the front page accidentally revealed a backup file of the entire website, which contained over 300 megabytes of private company emails, which were leaked to several torrents and across several sites on the Internet.^[141] It was suggested that the data leak could cost the law firm up to £500,000 in fines for breaching British Data Protection Laws.^[142]

In January 2011, BBC News reported that the law firm announced they were to stop "chasing illegal file-sharers". Head of ACS:Law Andrew Crossley in a statement to a court addressed issues which influenced the decision to back down "I have ceased my work ... I have been subject to criminal attack. My e-mails have been hacked. I have had death threats and bomb threats."^[140]

In August 2012, 4chan users attacked a third-party sponsored Mountain Dew campaign, Dub the Dew, where users were asked to submit and vote on name ideas for a green apple flavor of the drink. Users submitted entries such as "Diabeetus", "Fapple", several variations of "Gushing Granny", and "Hitler did nothing wrong".^[143][144]

On October 18, 2006, the Department of Homeland Security warned National Football League officials in Miami, New York City, Atlanta, Seattle, Houston, Oakland, and Cleveland about a possible threat involving the simultaneous use of dirty bombs at stadiums.^[145] The threat claimed that the attack would be carried out on October 22, the final day of the Muslim holy month of Ramadan.^[146] Both the FBI and the Department of Homeland Security expressed doubt concerning the credibility of the threats, but warned the relevant organizations as a precaution. The games proceeded as planned but under a higher level of security awareness.^[147] The threats came to light in the national media after Jake Brahm admitted to having posted the threats on 4chan and repeating them on other websites approximately 40 times.^[146]

Brahm did not expect the message to be taken seriously since he "would never take anything posted on 4chan as fact";^[149] an FBI official was quoted as saying the "credibility of [the threat] was beyond ridiculous".^[15] As a parody of the incident, 4chan temporarily added "Don't mess with football" as an additional rule for /b/.^[15] On October 20, 2006, Brahm turned himself in to federal authorities, and was charged with fabricating a fake terrorist threat and taken into custody.^[150] On February 28, 2008, he pleaded guilty to the federal charges. On June 5, 2008, he was sentenced to six months in prison, six months' house arrest, and ordered to pay $26,750 in restitution.^[151]

Around midnight on September 11, 2007, a student posted photographs of mock pipe bombs and another photograph of him holding them while saying he would blow up his high school—Pflugerville High School in Pflugerville, Texas—at 9:11 am on September 11.^[148] Users of 4chan helped to track him down by finding the perpetrator's father's name in the Exif data of a photograph he took, and contacted the police.^[152] He was arrested before school began that day.^{[153][154][155][156]} The incident turned out to be a hoax; the "weapons" were toys and there were no actual bombs.^[157]

Jarrad Willis, a 20-year-old from Melbourne, Australia was arrested on December 8, 2007, after apparently posting on 4chan that he was "going to shoot and kill as many people as I can until which time I am incapacitated or killed by the police".^[158] The post, accompanied by an image of another man holding a shotgun, threatened a shopping mall near Beverly Hills.^[159] While the investigation was still open, Willis was charged with criminal defamation for a separate incident^[160] but died before the case was heard.^[161]

On February 4, 2009, a posting on the 4chan /b/ board^[162] said there would be a school shooting at St Eskils Gymnasium in Eskilstuna, Sweden, leading 1,250 students and 50 teachers to be evacuated.^[163] A 21-year-old man was arrested after 4chan provided the police with the IP address of the poster. Police said that the suspect called it off as a joke, and they released him after they found no indication that the threat was serious.^[164][165]

On January 21, 2014, an anonymous poster started a thread on /b/ identifying a student named Westley Sullivan who apparently went to the same high school as the poster. The original post included a link to Westley Sullivan's Facebook profile, which has since been taken down, and a screenshot of a post which said "if fairview isnt closed tomorrow im going to blow it up", referring to Sullivan's high school, Fairview High School, in Boyd County, Kentucky. A few anonymous individuals went to Sullivan's Facebook profile and found his address, phone number, school ID number, school schedule and teachers, and other personal information. Information like his teachers and ID number had been posted directly, and the more personal information like his address was found in the EXIF data of some of the pictures posted on his profile. These individuals then contacted Fairview school officials and the local police department, as well as the FBI. The next day it was learned that police had arrested Sullivan in his home and he had been charged with 2nd degree terroristic threatening, a Class D felony in Kentucky.^[166][167]

On June 28, 2018, a man named Eric M. Radulovic was arrested following an indictment by the U.S. Department of Justice "on one count of transmitting in interstate and foreign commerce a threat to injure the person of another."^[168] The indictment alleged that Radulovic posted anonymously to /pol/ the day after the Unite the Right rally, communicating an intention to attack protestors at an upcoming right-wing demonstration, ostensibly to elicit sympathy for the alt-right movement. "I’m going to bring a Remington 700 and start shooting Alt-right guys. We need sympathy after that landwhale got all the liberals teary eyed, so someone is going to have to make it look like the left is becoming more violent and radicalized. It’s a false flag for sure, but I’ll be aiming for the more tanned/dark haired muddied jeans in the crowd so real whites won’t have to worry," wrote Radulovic, according to the indictment.^[168]

On November 29, 2010, Ali Saad, a 19-year-old, was arrested and had his home raided by the FBI for posting child pornography and death threats on 4chan. Ali had first visited 4chan "a week before [the FBI raid] happened". He admitted to downloading about 25 child pornography images from 4chan.^[169]

In January 2011, Matthew Riskin Bean, a 20-year-old man from New Jersey, was sentenced to 45 days in prison for cyberbullying on 4chan.^[170]

Collin Campbell, a U.S. Navy Machinist's Mate, was arrested in February 2011 after a fellow seaman found child pornography on his iPhone that he downloaded entirely from 4chan.^{[171][172][173][174]}

Ronald Ohlson, 37, was raided April 2011 at his upstate New York home by the Department of Homeland Security after he obtained child pornography from 4chan.^[175]

After 4chan reported a 15-year-old boy in California who posted child pornography, the United States Department of Homeland Security raided his home on June 7, 2011, and took all of his electronic items.^[176]

On February 17, 2012, Thaddeus McMichael was arrested by the FBI for child pornography charges after posting comments on Facebook claiming that he possessed child pornography.^[177] According to the official criminal complaint filed against Thaddeus, he admitted to obtaining child pornography from the /b/ board on 4chan.^[178]

On August 31, 2014, a large number of private photographs taken by celebrities were posted online due to a compromise of user passwords at iCloud.^[179] The images were initially posted on 4chan.^[180] As a result of the incident, 4chan announced that it would enforce a Digital Millennium Copyright Act policy, which would allow content owners to remove material that had been shared on the site illegally, and would ban users who repeatedly posted stolen material.^[181]

Also in August 2014, 4chan was involved in the Gamergate controversy, which began with unsubstantiated allegations about indie game developer Zoë Quinn from an ex-boyfriend, followed by false allegations from anonymous Internet users.^[182] The allegations were followed by a harassment campaign against several women in the video game industry, organized by 4chan users.^[183] Discussion regarding Gamergate was banned on 4chan due to alleged rule violations, and Gamergate supporters moved to alternate forums such as 8chan.^[184][185]

According to court documents filed on November 5, 2014, there were images posted to 4chan that appeared to be of a murder victim. The body was discovered in Port Orchard, Washington, after the images were posted.^[186] The posts were accompanied by the text: "Turns out it's way harder to strangle someone to death than it looks on the movies." A later post said: "Check the news for Port Orchard, Washington, in a few hours. Her son will be home from school soon. He'll find her, then call the cops. I just wanted to share the pics before they find me."^[186] The victim was Amber Lynn Coplin, aged 30. The suspect, 33-year-old David Michael Kalac, surrendered to police in Oregon later the same day; he was charged with second-degree murder involving domestic violence.^[187] Kalac was convicted in April 2017 and was sentenced to 82 years in prison the following month.^[188]

On July 14, 2019, 17-year-old Bianca Devins was murdered by 21-year-old Brandon Clark of Utica, New York after the two went to a concert together.^[189] The suspect took pictures of the victim's bloodied deceased body and posted it to Discord and his own Instagram page.^[190] The photos were widely shared on Instagram and other sites, particularly on 4chan where many users mocked and celebrated her death, saying she deserved it and praising the killer while depicting Devins as a manipulative young woman.^[191][192] Devins had developed a small following online and was a 4chan user herself.^[193]

On July 26, 2009, AT&T's DSL branch temporarily blocked access to the img.4chan.org domain (host of /b/ and /r9k/), which was initially believed to be an attempt at Internet censorship, and met with hostility on 4chan's part.^[194][195] The next day, AT&T issued a statement claiming that the block was put in place after an AT&T customer was affected by a DoS attack originating from IP addresses connected to img.4chan.org, and was an attempt to "prevent this attack from disrupting service for the impacted AT&T customer, and... our other customers." AT&T maintains that the block was not related to the content on 4chan.^[196]

4chan's founder Christopher Poole responded with the following:^[197][198]

Major news outlets have reported that the issue may be related to the DDoS-ing of 4chan, and that 4chan users suspected the then-owner of Swedish-based website Anontalk.com.^[199][200]

On February 4, 2010, 4chan started receiving reports from Verizon Wireless customers that they were having difficulties accessing the site's image boards. After investigating, Poole found out that only the traffic on port 80 to the boards.4chan.org domain was affected, leading members to believe that the block was intentional. Three days later, Verizon Wireless confirmed that 4chan was "explicitly blocked". The block was lifted several days later.^[201]

On March 20, 2019, Australian telecom company Telstra denied access to millions of Australians to 4chan, 8chan, Zero Hedge and LiveLeak as a reaction to the Christchurch mosque shootings.^[202]