Beyond targeting individuals, online vigilantism can comprise significant collective practices among categories of social groups and therefore profoundly be embedded in reshaping the structures of social positions. By tracing the rise and fall of a specific user-generated music videos, hanmai, and the social media platform facilitating its production and circulation, Kuaishou, this chapter explores how vigilant practices including denunciating, shaming, and humiliating are involved in the transitioning Chinese society’s class stratification process, in particular in the making of distinction between underclass and middle-class identities among younger generations in the digitally-mediated world. After two years of online ethnography, the study first argues that with the new affordable digital technologies, the Chinese underclass youths for the first time attempted to realize a collective underclassness in creating and interacting with hanmai videos, in which class differences were reinforced with rhetoric and affective denunciations. However, these non-vigilante denunciations transformed the underclass into subjects of a larger scale online vigilantism and, later, state-led surveillance. Middle-class Internet users endeavoured to distinguish from the underclass by condemning the aesthetic, moral, and technological vulgarity implied in hanmai videos. The state surveillance also reached the underclass user-generated content in order to pursue a positive rather than vulgar representation of the underclass. The technologically-mediated visibility of Chinese underclass youths in the form of hanmai videos transformed from empowering social recognition to triggering various disciplinary forces both from the middle-class audiences and state power in cooperation with social media platforms.