Research summaryDarknet marketplaces (DNMs) are global digital marketplaces used primarily to buy and sell illicit drugs online. High rates of adulterated substances have contributed to the creation of harm reduction policies by DNM administrators to address growing rates of overdose worldwide. This paper explores the extent to which harm reduction occurs in buyer feedback of Adderall and Oxycodone purchased on AlphaBay and how these comments are impacted by AlphaBay's administrator‐led “harm reduction” policy. This study finds that harm reduction strategies are present in buyer feedback of Oxycodone and Adderall pills, but AlphaBay's policy has very little impact on the preexisting harm reduction communication within buyer feedback.Policy implicationsInternational policy proposals have placed emphasis on addressing the overdose crisis through harm reduction programs that provide people who use drugs with the necessary services and resources to buy and use drugs safely. There have been very few proposals that have considered how these programs can address the unique setting of buying and using drugs purchased on DNMs. Communication occurring among DNM buyers reveals how harm reduction strategies are being employed by users purchasing drugs from DNMs. In particular, these findings offer insight into the shared experiences of drug buyers in anonymous settings and the strategies they are using to protect one another from overdose and other unwanted side effects often caused by adulterated substances. Understanding these strategies highlights the ways in which street‐based harm reduction programs can extend their services to online environments to assist buyers with making safe and informed decisions when using substances purchased online.