One recurring criticism about MOOCs is the fact that few learners complete the course they have registered for and finally earn a certificate. This article delves into this issue on the basis of the analysis of the MOOC « Découvrir la science politique » (Louv3x, on the edX platform). With a retention rate of 18%, this MOOC scores above the average. In order to refine empirically the approach, and building on the existing literature, the authors distinguish between levels of active retention and passive retention. In this perspective, the paper digs into data collected throughout the MOOC and explores several explanatory factors of retention and motivation for the learners and the teaching team.