Platform-based on-demand delivery services are rapidly developing in urban areas, especially in the food sector, raising new issues for urban planners, especially in the field of transport. Based on a survey of over 100 couriers conducted in 2018 in the municipality of Paris (France), this work aims at analyzing the profile, delivery activity and mobility practices of the couriers working for these platforms. The main objective is to show how mobility practices are shaped by the characteristics of digital work in the urban delivery sector, and to highlight new challenges for urban authorities and research. Compared to other studies, our work is based on quantitative data and distinguishes three categories of couriers, depending on whether they have another activity: students, people with another paid job, and people with no other paid or non-paid activity. Findings show that these three categories have different characteristics, regarding age, education, residential location, the intensity of delivery activity and the characteristics of mobility practices, especially regarding the transport modes used. The article ends with the discussion of a number of new challenges for both urban authorities and researchers regarding the sustainability of these new forms of digital work in urban delivery.