Activism online is often presented as thin, low-cost engagement, accomplished by clicking Like on Facebook or using Twitter hashtags to express political opinions. Some activists, however, use the Internet differently, making political statements using methods that are illegal or legally questionable. Anonymous—a network of activists, hackers, and provocateurs—is arguably the most well-known of such actors. Participation in Anonymous actions can carry personal risks, as activists associated with Anonymous have faced legal consequences—from fines to imprisonment—in several countries. Using material generated from participant observation in Anonymous chat rooms, I analyze which risks of participation are publicly identified, how they are discussed, and the individual and collective strategies of risk-mitigation. This analysis makes a unique contribution by investigating a case that suggests that the subjective experience of risk is acknowledged and accounted for by activists online. I suggest that this has consequences for how researchers should approach political engagement online and the study of high-risk activism in the digital age.