Over the past two decades, research has identified concrete, practical activities that boost character virtues such as gratitude, awe, and generosity. But evidence suggests that these activities don’t work equally well for every person or context. So which activities are the best “fit” for which types of people or life circumstances? We will address that big question through innovative use of Greater Good in Action (GGIA), our free, mobile-optimized website featuring more than 70 research-based activities that support a range of character virtues. We will collect data from GGIA’s large user base (>500,000 annual visitors) about their personal characteristics and circumstances. Then we will analyze these data to determine the best-fitting—and most effective—practices for different individuals and contexts. Then, based on these data, we will create an algorithm that gives users personalized recommendations for the GGIA practices most likely to improve their character development and well-being. This will require that we first enhance the design and functionality of GGIA to make it even more engaging to its visitors, thereby increasing the quantity and quality of the data we collect. Our analyses of these data will explore how people’s personal characteristics and circumstances can predict the GGIA activities with which they’re most likely to engage and from which they derive the greatest benefit. We will also experimentally test competing theories about the best approach to matching a person with the right positive activities before we finally build, launch, and improve upon our recommendation algorithm. These upgrades to GGIA will deepen public engagement with the science of character and help nurture character virtues in our hundreds of thousands of users. Ultimately, this project will also yield ground-breaking scientific insights about character virtue development and well-being that could inform best practices in many clinical and educational settings.