Human mobility within geographical space is a fundamental dimension of individual life courses, enabling access to new opportunities, experiences, and resources. The spatial concentration of employment and housing opportunities in urban centers acts as a primary driver of rural-to-urban migration, particularly in contexts of economic restructuring and regional disparities.In recent decades, France and especially its formerly industrialized regions, which were historically centered on metallurgy and steel production, has experienced a profound economic crisis characterized by rising unemployment and industrial decline. This situation has been further exacerbated by the ongoing transition toward emerging industries that are increasingly oriented toward sustainable development priorities.Within this context, the Grand Est region stands out as a critical case study: despite hosting strategic urban hubs such as Strasbourg, it records the lowest population growth in France. Many of its economically fragile areas face a persistent exodus of young, active populations, accelerating demographic aging and undermining regional vitality. The capacity of a region to retain or attract young and skilled individuals is thus a pivotal determinant of its long-term socioeconomic resilience.This paper proposes an in-depth analysis of residential trajectories and professional integration among young adults in France. By adopting a territorial approach and degree of urbanisation, the study will investigate local demographic dynamics and their influence on spatial mobility patterns. The research will specifically examine residential and occupational mobility, while systematically considering the role of sociodemographic characteristics and geographical origins in shaping these processes.MethodsThe data used are those of the permanent demographic sample (EDP) and the population census, which are very rich and precise. They provide information on the evolution of individual lives, taking into account socio-demographic characteristics, places of residence, work, housing, family and professional careers. Our objective is to examine the impact of sociological and geographical factors on life-course decisions, using statistical probability and trajectory analysis.This study explores how young people’s use of space evolves during their transition to adulthood from 2011 to 2019. The goal is to analyse the sustainability and transformation of spaces through their demographic and spatial trajectories.The primary mobility patterns examined include arrivals, departures, immobility, intra-regional mobility, and return migration. Explanatory variables encompass sex, parental status, marital status, age, employment trajectory, and the degree of urbanization of the residence.The methodology integrates sequence and clustering analyses to identify trajectory patterns, multivariate and logistic regression analyses to profile individuals, and territorial classifications based on life course outcomes. A qualitative approach using semi-structured interviews further enriches the analysis.Key findingsOur findings indicate that geographical origin, specifically region and degree of urbanisation, significantly influences individuals’ migration trajectories, despite the predominant trend of mobility toward highly dense urban areas. Life course trajectories also reveal notable gender differences: women are more likely to undertake long-distance migration and pursue extended studies in new regions without returning to their region of origin, while men tend to either remain in place or return to their region of origin after periods of higher education mobility