Many people who experience problem gambling, alcohol misuse, or binge eating do not seek professional help. Instead, they may turn to online interventions to help them change their behaviour. This article reviewed studies on online interventions for gambling, alcohol misuse, and binge eating. Specifically, it looked at how effective different types of interventions were. It also looked at the techniques these interventions used to change behaviours. The researchers found five behaviour change techniques that were often used in interventions that were both effective and of high quality. For example, monitoring one’s own behaviour was the most common technique in these interventions. These results can help researchers develop effective online interventions for harmful behaviours.