The "Momo Challenge" as it was known, was a hoax and an Internet urban legend that was rumored to spread through social media and other outlets. It was reported that children and adolescents were being enticed by a user named Momo to perform a series of dangerous tasks including violent attacks, self-harm and suicide. Despite claims that the phenomenon had reached worldwide proportions in July 2018, the number of actual complaints was relatively small and no law enforcement agency has confirmed that anyone was harmed as a direct result of it.
The challenge was reported to become "a worldwide phenomenon" in 2018 after an Indonesian newspaper reported that it had caused a 12-year-old girl to kill herself. Awareness grew in February 2019 after the Police Service of Northern Ireland posted a public warning on Facebook, and American media personality Kim Kardashian posted on her Instagram Story pleading for YouTube to remove alleged "Momo" videos. The challenge has (or claims to have) existed in the United States, Canada, the United Kingdom, Australia, Ireland, India, Luxembourg, Belgium, Malaysia, Peru, Pakistan, Germany, the Philippines, Singapore, South Korea, Thailand, France, Italy, Switzerland, Indonesia, Brunei, Hong Kong, Spain, Portugal, Mexico, Colombia, Chile, Bulgaria, Argentina, Brazil, and the Dominican Republic.
The Momo Challenge gained the public's attention in July 2018, when information on the supposed challenge was outlined and discussed in videos produced by a YouTuber, ReignBot. Targeting teenagers, people presenting themselves as a character named Momo on WhatsApp messages try to persuade people to contact them through their cell phone. As with other Internet hoaxes presented as challenges such as "Blue Whale", players are then instructed to perform a succession of tasks; refusal to do so is met with threats. Messages are subsequently accompanied by frightening or gory pictures. Although the panic eventually died down throughout the rest of 2018, it returned in a much more pervasive form in early 2019, when it was claimed that Momo was being inserted into seemingly innocuous YouTube and YouTube Kids videos about Peppa Pig and Fortnite; these claims were repeated by the group National Online Safety.
Although authorities have not confirmed any physical harm resulting from this, or even that a sustained exchange of messages took place between the Momo character and anybody, police forces and school administrations on several continents have issued warnings about the Momo Challenge and repeated common advice about Internet safety. WhatsApp is encouraging its users to block phone numbers engaging in this practice and to report them to the company.
Commenting on the numerous rumours of suicide related to the Momo Challenge, web security experts and folklorists studying urban legends have stated that the phenomenon is likely a case of moral panic: a sensationalized hoax fuelled by unverified media reports.  Benjamin Radford says "the Blue Whale Game and the Momo Challenge have all the hallmarks of a classic moral panic", "fuelled by parents' fears in wanting to know what their kids are up to. There's an inherent fear in what young people are doing with technology." By September 2018, most phone numbers supposedly associated with "Momo" were out of service. The founder of fact-checking site Snopes, David Mikkelson, doubts anybody actually came to any harm and said the whole thing "may primarily be a product of bullies and pranksters latching onto a handy mechanism to goad and torment vulnerable youngsters rather than an intrinsic part of a particular social media challenge."
In response to the reports in early 2019, YouTube has said that it has "not received any links to videos showing or promoting the Momo challenge on YouTube" but permits news stories and videos intended to raise awareness of and educate against the alleged phenomenon. The website has demonetized all videos mentioning Momo, including those of news organizations, saying such content violates its advertiser-friendly content guidelines. It has also placed advisory warnings on some Momo videos alerting viewers of "inappropriate or offensive" content.
In India, the Central Bureau of Investigation (CBI) in West Bengal indicated on August 29, 2018, that claims reported in the media about the death of two teens being linked to the Momo Challenge were "far fetched and devoid of any evidence". CBI believes most of the large volume of Momo Challenge invitations in India originate locally as pranks sent to spread panic. A CBI spokesperson stated that "so far, the game has not claimed any victim, nor has anyone approached us saying they have played even the first level of it." The CBI statement followed weeks of news coverage about unconfirmed cases. After being alerted by a youth who received a Momo Challenge invitation, police in West Bengal issued a warning, and the cybercrime unit opened an investigation. The Mumbai police had previously started to warn the population, although no complaints were filed. Police did not confirm any role the Momo Challenge might have played in the death of a girl in grade 10 who died by suicide after leaving a note expressing discouragement with low grades or the suicide of an engineering student in Madras. The Odisha Police, while issuing an advisory asked the media to refrain from publishing unconfirmed reports linking teen death to the Momo Challenge.
Pakistan's Minister of Information Technology announced the government intended to draft legislation making it a crime to distribute both the Momo Challenge and the Blue Whale Challenge.
Police authorities in the Philippines issued warnings to parents to be vigilant of their children's online activity after an 11-year-old boy died from apparent suicide by drug overdose on 11 January 2019, linking the incident to the viral challenge, although no official confirmation of direct relation to the incident has been established by the authorities. In the aftermath of the reports, Raffy Tulfo and other YouTubers voiced their condolences to the family, encouraging that children be monitored by their parents. They also linked the Blue Whale Challenge to the incident.
In France, a group at the State Department was reviewing the situation daily in late July 2018. A complaint was filed in November by a father whose son died by suicide.
In Germany, the police were only aware of mentions made in chain letters. They are asking the population to act prudently when faced with that kind of cell phone contact.
The Luxembourg police confirmed one case on its territory, but no harm was caused.
The Belgian Public Prosecutor's Office reported on 6 November 2018 that a 13-year-old boy had been the victim of the Momo Challenge and hanged himself.[better source needed]
Spain's National Police warned people to stay away from new "challenge" applications that pop up on WhatsApp, indicating the Momo phenomenon was in vogue among teenagers.
In the United Kingdom, some school administrations relayed warnings about the phenomenon. Reports on and awareness of the alleged challenge rose in February 2019 after the Police Service of Northern Ireland issued a public warning. British authorities say the challenge is being used by cybercriminals to gain personal identity information. Responding to tabloid coverage which asserted the challenge to be true, the NSPCC, the Samaritans, and the UK Safer Internet Centre have issued statements stating that the Momo Challenge is a hoax. The parent who alerted the press to the Momo Challenge subsequently said her child had not received messages from "Momo", but was merely told about it in a school playground conversation. Nevertheless, authorities and the media issued online safety precautions. Nicola Harteveld (who said her son was targeted by the challenge) and clinical psychologist Anna Colton warned on ITV's daytime TV show This Morning not to search for Momo online and advised parents to be aware of their children's activity online.
In the Canadian province of Quebec, local police forces of Longueuil, Sherbrooke and Gatineau indicated that people in their jurisdiction had been approached to participate in the Momo Challenge but did not report any victims. They asked people not to use the phone number provided in the WhatsApp messages and to send screen capture images of their phone to police authorities. The Royal Canadian Mounted Police and other police forces say they are monitoring the spread of the phenomenon but could not confirm any actual victim.
Mexican authorities investigating Internet crimes distributed detailed information to parents about the methods of the scheme. They suspect it has spread through a Facebook group frequented by young people. They warned those caught in the scheme risked self-harm, hacking and extortion.
In early August 2018 in the United States, various local police forces warned the population about the dangers of the phenomenon. Some jurisdictions have received several complaints, but no jurisdiction reported anybody being harmed. The Momo character has also appeared in the popular game Minecraft in the form of in-game skins and unofficial mods created by the game's users. A police officer in Ohio was concerned to see Momo in his son's copy of the game, worried about the possibility that the mod could lead to participation in the Momo Challenge. After news reports started to outline the link between the Minecraft mod and the Momo Challenge, Microsoft announced it was taking measures to "restrict access to the mod" in question.
In Argentina, despite several media reports tentatively establishing a relationship between the Momo Challenge and the suicide of a 12-year-old girl from Ingeniero Maschwitz, no link has been confirmed by authorities.
Authorities in Brazil have not confirmed any case linked to the Momo Challenge. The national SaferNet non-profit organization has been approached by concerned parents and warned that this is only one of a variety of schemes to extort money and information from people.
The Colombian police have not confirmed news reports linking the death of two youths in Barbosa to the Momo Challenge in early September.
Early news reports stating the image of Momo was of a sculpture by Japanese artist Midori Hayashi turned out to be incorrect. Hayashi indicated that it was not her piece, and Internet users identified Link Factory, a Japanese special effects company, as the correct author of the sculpture.
The sculpture has bulging eyes and a beak-like mouth. It also had human-like breasts. Pictures of the sculpture were first posted online in 2016, when it was publicly exhibited. The firm denies any involvement with the hoax. Japanese artist Keisuke Aiso confirmed in March 2019 that the sculpture had been thrown away in 2018, after its materials (natural rubber and plant oils) had decomposed.
Video games based on the Momo Challenge have been published by various independent developers — in July 2018 by SirFatCat and Indie_RU, in August 2018 by Dymchick1 and in October 2018 by Caffeine. The player has to do various tasks and the goal is usually to survive before getting rescued.
On March 9, 2019, Saturday Night Live parodied the meme with a video featuring Kate McKinnon as a terrifying chicken-suited fast food mascot named "Bok Bok," whom the narrator says "does bear a slight resemblance to the internet urban legend Momo." The narrator says, "We promise, Bok Bok is not Momo in a chicken suit," despite also being "a human-bird hybrid that loves the company of children." At the end, the narrator admits, "Yeah, that's probably Momo."
In July 2019, Orion Pictures said it was developing a film adaptation, with producers Roy Lee (with his production company Vertigo Entertainment) and Taka Ichise.