Personal informatics (PI) has gained great attention and become ubiquitous in people’s everyday lives. Although an increasing number of studies set out to explore the social aspects of PI, there remains an unaddressed opportunity for a structured, systematic review to understand why and how the sharing happened, to inform future design and research. This systematic review summarizes the last 13 years of research on the diverse cases of shared PI practice from ACM, PubMed, and IEEE. 100 papers were analyzed, and four types of sharing were identified: Interpersonal targeting, Public broadcasting, Group monitoring, and Community exchanging. Notably, sharing extends beyond data exchange, evolving into a collaborative process across different PI stages. The review offers a taxonomy of shared PI practices and delineates design possibilities, facilitating future exploration in the field. Additionally, it identifies trends and patterns within existing work, suggesting design opportunities for future explorations of shared personal informatics.