This paper discusses the importance of effective engagement with digital behavior change interventions (DBCI) and provides guidance on how to promote it. It highlights the need to understand the relationship between engagement with the digital intervention and the desired behavior change. The paper argues that it is more valuable to establish and promote 'effective engagement' rather than simply more engagement. Effective engagement is defined as sufficient engagement with the intervention to achieve intended outcomes. The paper also discusses the challenges of measuring engagement and the need for valid and efficient combinations of measures to develop and test multidimensional models of engagement. It emphasizes the importance of user-centered and iterative approaches to intervention design, using mixed methods and in-depth qualitative research to progressively refine the intervention to meet user requirements. The paper also discusses the importance of tailoring interventions to individual needs and combining DBCIs with human support. It highlights the need for further research to understand how to design interventions that are accessible and engaging for people with lower levels of education, literacy or computer literacy. The paper concludes that effective engagement can only be understood through valid, reliable and comprehensive means of assessment, and that a mixed method multidimensional approach will provide a more comprehensive picture of how users are engaging with DBCIs. The paper also emphasizes the importance of considering the social and therapeutic context in which interventions are delivered.This paper discusses the importance of effective engagement with digital behavior change interventions (DBCI) and provides guidance on how to promote it. It highlights the need to understand the relationship between engagement with the digital intervention and the desired behavior change. The paper argues that it is more valuable to establish and promote 'effective engagement' rather than simply more engagement. Effective engagement is defined as sufficient engagement with the intervention to achieve intended outcomes. The paper also discusses the challenges of measuring engagement and the need for valid and efficient combinations of measures to develop and test multidimensional models of engagement. It emphasizes the importance of user-centered and iterative approaches to intervention design, using mixed methods and in-depth qualitative research to progressively refine the intervention to meet user requirements. The paper also discusses the importance of tailoring interventions to individual needs and combining DBCIs with human support. It highlights the need for further research to understand how to design interventions that are accessible and engaging for people with lower levels of education, literacy or computer literacy. The paper concludes that effective engagement can only be understood through valid, reliable and comprehensive means of assessment, and that a mixed method multidimensional approach will provide a more comprehensive picture of how users are engaging with DBCIs. The paper also emphasizes the importance of considering the social and therapeutic context in which interventions are delivered.