This study aims at renewing traditional dialectological atlases to provide a mapping of pronunciation variants by using crowdsourcing. Based on French spoken in France, Belgium and Switzerland, it focuses on mid vowels whose quality may be open or close and shibboleths such as final consonants which may be maintained or deleted, as a function of speakers' background. Over 1000 subjects completed a questionnaire in which they were asked which one of the two possible pronunciations was closer to their most usual pronunciation. Their responses for 70 French words are displayed in the form of maps. This graphical layout enables the general public and phoneticians to readily visualise where phonological constraints such as the “loi de position” are violated.