Recent years have marked a shift in selling and buying illicit psychoactive drugs from darknetcryptomarkets to publicly accessible social media and messaging platforms. As more users turnto procuring drugs this way, the role of digital harm reduction has become particularly urgent.However, one of the main obstacles complicating the implementation of digital harm reductionis the increasingly automated content moderation by the social media platforms. While someplatforms are less restrictive about harm reduction content (e.g., TikTok), others implementhigher degrees of moderation, including the removal of individual content and banning ofentire profile pages (e.g., Instagram). This article discusses community guidelines of fivepopular social media and messaging platforms and their content moderation tools. It aims tohighlight how these guidelines may be inadvertently curbing the dissemination of harmreduction and health promotion materials, and erroneously interpreting it as a promotion ofdrug use and sales. The discussion concludes that digital harm reduction requirestransdisciplinary collaboration of professional organizations, researchers, and social mediaplatforms to ensure reliable implementation of digital harm reduction, and help build saferdigital communities.