When Matheus Dominguez was 16, YouTube recommended a video that changed his life.

He was in a band in Niterói, a beach-ringed city in Brazil, and practised guitar by watching tutorials online.

YouTube had recently installed a powerful new artificial intelligence system that learned from user behaviour and paired videos with recommendations for others. One day, it directed him to an amateur guitar teacher named Nando Moura, who had gained a wide following by posting videos about heavy metal, video games and, most of all, politics.

In colourful and paranoid far-right rants, Moura accused feminists, teachers and mainstream politicians of


The Party of YouTube

Down the rabbit hole

"Dr. YouTube"

An "ecosystem of hate"

"The dictatorship of the like"