Often promoted by planning and transportation authorities as one of the principal ways to reduce the impact of mobility on transportation gas emissions, carpooling practices have increased over recent decades for daily commuting as well as long-distance travel. However, mainly due to the lack of data, little is known about the geography of these trips. On the one hand, the intensity of supply and demand may favor urban areas alongside common transportation systems. On the other hand, the scarcity of public transport in rural areas or small towns can support the growth of these shared mobilities. This article presents a geographical investigation of carpooling patterns in France and to overcome the lack of survey-data, it proposes an original method based on massive data collected from the Blablacar platform, national leader for this type of online services. After a review of the literature, the paper presents the main elements of the methodology implemented to collect and analyze the web data of carpooling. The analysis presents new findings that reveal the geographical features of car-sharing in France. The impact varies depending on the size of the towns, the presence of regional and inter-regional urban systems, and the tourism specialization of rural areas. The study also emphasizes the unique position of Paris and the pivotal role of intermediate towns.