Many previous studies focused on harm reduction and harm prevention efforts in land-based gambling. But it is not clear whether their findings can be applied to online gambling. In this article, the authors review harm reduction and prevention efforts for online gambling. They discuss universal measures that aim to prevent and reduce harm at the population level. These measures include addressing the delivery and availability of online gambling opportunities (e.g., regulations to restrict availability and online marketing). The authors also discuss selective measures that target vulnerable populations at a greater risk for gambling-related problems. These measures include age restrictions, pre-commitment tools, and self-exclusion. Finally, the authors discuss indicated interventions aimed at people with a greater risk of gambling-related problems. These interventions include using artificial intelligence (AI) tools to identify patterns of problematic behaviour; personalized feedback; and online therapeutic options.