Background: Platform-based fast delivery is developing rapidly in many cities across the world, especially in the food sector. Yet knowledge about the characteristics and the activity patterns of delivery couriers is scarce, especially in terms of their mobility behavior. Methodology: Based on two questionnaire surveys conducted in 2020 and 2021 with 300 and 500 couriers respectively, this article analyses the profiles, motivations and mobility patterns of couriers working in Paris (France), with a focus on the impacts of the pandemic. Results: First, the analysis of the profiles and motivations of couriers reveals that platform-based delivery is largely a temporary activity performed by young males of foreign origin, and undertaken as a student job or an entry to the labor market. Second, data on mobility patterns confirm that platform-based delivery is a dangerous activity with a high risk of road accidents. Moreover, many couriers break the law in order to increase their income by using motorized two-wheelers that are not legally permitted in France. We also show the use of shared bikes, which seems to be a great support tool for couriers who are starting work in this sector or have a problem with their own bikes. Third, the pandemic prompted many students to become platform-based delivery couriers in order to compensate for the lack of student jobs. It also worsened the working conditions of the majority of platform-based couriers. These findings raise new urban policy challenges and also new avenues for research in terms of topics and methods.