He was a member of a band in Niterói, a city surrounded by beaches in Brazil, and he improved his guitar skills by watching online tutorials. YouTube had recently implemented a sophisticated new artificial intelligence system that learned from user activity and suggested videos based on their preferences. One day, he was led to an amateur guitar instructor named Nando Moura, who had amassed a large following by posting videos about heavy metal, video games, and primarily politics. In his vibrant and paranoid far-right monologues, Moura accused feminists, educators, and mainstream politicians of engaging in elaborate conspiracies. This captivated Dominguez. As he spent more time on the platform, YouTube recommended videos from other far-right personalities, including a politician named Jair Bolsonaro, who at the time was not well-known nationally but was a popular figure within YouTube's far-right community in Brazil, where the platform had a larger audience than all but one TV channel. Bolsonaro was elected President the following year. "YouTube became the main social media platform for the Brazilian right," stated Dominguez, who is now a 17-year-old aspiring politician and credits YouTube for his shift towards far-right beliefs. YouTube's success in keeping users engaged has inadvertently benefitted extremist groups, as discovered in a recent investigation in Brazil, the company's second-largest market. The far right in the country credits YouTube's recommendation engine for the rapid growth of their movement. Research shows that the platform's search and recommendation system often directs users towards far-right and conspiracy channels. This has had significant consequences, with classrooms disrupted by students quoting conspiracy videos, parents receiving dangerous health advice from YouTube instead of medical professionals, and overall hindering the nation's efforts to combat diseases like Zika. Viral videos have led to death threats against public health advocates, while right-wing YouTube stars have entered politics, some alongside Bolsonaro, and continue to use the platform to govern the fourth-largest democracy through trolling and provocation. YouTube's recommendation system is designed to maximize watchtime and does not favor any political ideology, but can lead users towards extreme content through emotions like fear, doubt, and anger. This system now drives 70% of total time on the platform, bringing in over $1 billion a month, and has been called a powerful radicalizing instrument by social media scholar Zeynep Tufekci. The company disputes claims that the system directs users towards extremism. However, representatives of the company admitted some of the findings and vowed to implement changes. Farshad Shadloo, a spokesperson, stated that YouTube has made significant investments in policies, resources, and products to reduce the spread of harmful misinformation. He also mentioned that authoritative content is thriving in Brazil and is highly recommended on the site. Danah Boyd, founder of Data & Society, attributed the disruption in Brazil to YouTube's relentless drive for viewer engagement and the revenue it generates. Despite corruption scandals and a severe recession already impacting Brazil's political landscape, Boyd expressed concern about YouTube's growing influence on democracies worldwide. Maurício Martins, the local vice president of Bolsonaro's party in Niterói, credited YouTube for recruiting most of the party members, including himself. He highlighted how YouTube's auto-playing recommendations served as his political education. The platform's political influence is also evident in Brazilian schools, where students are increasingly making extremist claims, often citing YouTube stars like Moura. Carlos Jordy, a City Council member, exemplifies YouTube's influence as he turned to the platform for political inspiration and accused local teachers of conspiring to indoctrinate students into communism. He said that the videos helped him gain a large following and led to his quick rise to the federal legislature. He believes that without social media, he would not have achieved this success and Jair Bolsonaro would not have become president. Researchers at the Federal University of Minas Gerais studied how YouTube influences users' perceptions and found that right-wing channels in Brazil were growing faster and shaping the site's political content. Positive mentions of Bolsonaro increased after YouTube changed its algorithm, even though polls showed he was unpopular. A team at Harvard's Berkman Klein Center investigated if YouTube's recommendation engine played a role in the Brazilian far right's popularity on the platform. They found that the platform moved users from one video to the next, potentially contributing to the rise of right-wing content. They discovered that following users watching videos on politics or entertainment, YouTube's recommendations often preferred right-wing, conspiracy-filled channels like Moura's. Significantly, viewers who watched one far-right channel were frequently shown many more. The researchers concluded that the algorithm had brought together previously marginalized channels and then cultivated an audience for them. One of these channels belonged to Bolsonaro, who had been using the platform to post hoaxes and conspiracies for a long time. Despite being an early adopter of YouTube, his online following had not significantly expanded his political base, which was almost non-existent at a national level. However, when Brazil's political system collapsed, YouTube's popularity in the country soared. Bolsonaro's views remained the same, but the far-right on YouTube, where he was a prominent figure, experienced a surge in viewership, preparing a large number of Brazilians for his message during a period when the country was ready for a political change. YouTube disputed the researchers' methodology and claimed that their internal data contradicted the findings. Nevertheless, the company refused to provide the Times with the data or certain statistics that could confirm the accuracy of the researchers' findings. The spread of conspiracies was not confined to politics. Numerous Brazilians who turned to YouTube for health information were frightened by videos claiming false information about Zika being spread by vaccines or insecticides. These videos gained popularity by making sensational claims and offering supposed hidden truths, leading to a public health crisis as people refused vaccines and insecticides. This misinformation has had severe consequences in poorer communities like Maceió, where patients are defying medical advice based on what they see online. Physicians are facing a constant battle against misinformation from sources like Google and YouTube, ultimately resulting in a resurgence of diseases like Zika in some areas of Brazil. The medical community in Brazil is struggling to combat the spread of false information through social media. The researchers from Harvard University discovered that YouTube often directed users searching for information on Zika, or those watching a reputable health video, towards conspiracy channels. A spokesperson for YouTube acknowledged this unintentional behavior and stated that the company would make changes to how videos related to Zika are shown in search results. As the far-right movement grew, conspiracy videos were used to target individuals, such as women's rights activist Debora Diniz, who advocated for abortion rights. These videos accused her of being involved in supposed Zika plots, suggesting that those working to help Zika-affected families were actually behind the disease. Conspiracy channels began referencing each other, leading YouTube's recommendation system to link their videos together, creating a false narrative. Diniz received threats of rape and torture as a result of these conspiracy theories. Diniz stated that many claims made in Küster's videos were echoed, though Küster never explicitly endorsed the threats, which kept him within YouTube's guidelines. When the university where Diniz taught received a warning that she and her students would be shot, and the police could no longer guarantee their safety, she left Brazil. Diniz believes that the YouTube recommendation system has created a breeding ground for hate speech, leading to a dangerous cycle of misinformation and incitement to violence. She emphasizes the need for companies to take responsibility for their role in promoting harmful content. “Morally, they have a responsibility.” As false information spreads on YouTube, content creators have targeted aid organizations involved in controversial issues such as abortion. Some people who had previously relied on these organizations began to question the validity of the videos and started avoiding them. In Brazil, this trend is known as “linchamento” — lynching. Bolsonaro was one of the first to spread misleading videos in 2012, falsely accusing leftist academics of planning to distribute “gay kits” in schools to convert children to homosexuality. Jordy, a follower of Bolsonaro from Niterói with tattoos, was not bothered to hear that his own YouTube campaign accusing teachers of promoting communism had negatively impacted their lives. One of the teachers, Valeria Borges, mentioned that she and her colleagues had received numerous hateful messages, creating a fearful atmosphere. Jordy admitted that causing fear was his intention. He stated, “It’s a cultural battle we are engaged in. This is why I entered office.” The epicenter of political YouTube content may be the Movimento Brasil Livre headquarters in São Paulo, which was established to advocate for the impeachment of President Dilma Rousseff in 2016. The members of the group are typically young, middle-class, right-wing, and very active on the internet. Renan Santos, the national coordinator, pointed to a door labeled "the YouTube Division" and described it as the central hub of the group. Inside, a group of young men were working on editing software, with one of them editing an image of Benito Mussolini for a video arguing that fascism was wrongly associated with the right. However, some members of the group are concerned about the impact of social media on democracy. Santos referred to social media as a "weapon" that some individuals close to Bolsonaro want to use to pressure institutions in a way that he considers irresponsible. The group's co-founder, Pedro D'Eyrot, mentioned the concept of the "dictatorship of the like," where reality is shaped by the most viral message. At the same time, a popular two-hour YouTube video titled "1964" was spreading across the nation, arguing that the military coup of that year was necessary to protect Brazil from communism. This video influenced Dominguez, a teenager learning to play guitar, to believe that his teachers had exaggerated the atrocities of military rule. On the other hand, Borges, a history teacher criticized in YouTube videos, was reminded of the military curfews, disappeared activists, and police brutality of that time. She expressed concerns that she may face similar violence in the future. Matheus Dominguez, who credited YouTube for guiding his shift towards far-right political views, was shown recording a YouTube video in Niterói, Brazil. YouTube has thrived by engaging users, but this has inadvertently benefited extremist groups, as evidenced by a recent investigation in the company's second-largest market.