BACKGROUND: Stress has a negative impact on the experience of individuals with a cardiovascular disease—both directly (e.g., physiologic effects of stress may worsen cardiovascular disease) and indirectly (e.g., leads to higher perceived symptom severity). Therefore, stress management has become an extensively researched form of psychological therapy for these individuals, and is increasingly offered through the internet. Advantages of internet-based interventions include being time efficient (e.g., cut travel time), reducing waiting-lists, and increasing access for some sub-groups of the population (e.g., those living in rural and remote areas). Internet-based interventions also have the potential to integrate effective features of face-to-face interventions (e.g., tailored feedback, monitoring), but offer the scalability needed for public health interventions. However, up to 60% of individuals do not respond to these interventions, and for these individuals offering different types of support or increasing the intensity of the support provided is necessary. An innovative trial design to develop time-varying, adaptive interventions to maximize clinical effectiveness is the Sequential multiple assignment randomized trials (SMARTs). However, despite increasing popularity, SMARTs remain relatively new to intervention researchers.