Health-harmful norms persist because they fulfill a socially valued function. In many Nigerian communities, female genital cutting (FGC) is practiced because it is believed to discourage sex outside marriage, outweighing its perceived costs for many households. This paper examines the impact of the expansion of fast internet on FGC in Nigeria. Our findings indicate that exposure to fast internet reduces both the prevalence of FGC and support for it. The effect does not appear to be driven by exposure to explicit anti-FGC content online. Instead, we find that fast internet affects FGC by reducing premarital sex stigma, thereby decreasing the perceived benefits of the practice. These findings provide evidence on how health-harmful norms evolve as the value of their function changes, with implications for designing effective interventions.