Résumé : Little is known about crowding perception on events and the link with objective visitor counts and visitor’s behavior. This research aims to fill this gap by collecting WiFi sensor counts and comparing them with perception ratings of visitors and police and first aid data of Europe’s largest outdoor urban festival: the Ghent festivities. During 48 h visitors were asked to rate the human crowding, spatial crowding and pleasure on two event plazas and one passageway within the festivities zone. The results show that spatial crowding ratings are a better indicator for visitor counts than human crowding ratings. On two locations a pleasure drop occurred each night, which cannot be linked to the visitor counts, but it can be linked to people’s ratings of crowding as follows: pleasure dropped when the human crowding ratings exceeded 3 and if the spatial crowding ratings increased above 3 on a five-point rating scale during the pleasure drop. In a last step, two datasets on visitor behavior were included in the analysis, i.e., number of police interventions and first aid visits. The analysis of these datasets shows that behavior, crowding and emotional response are linked at the Ghent festivities (e.g., at Vlasmarkt most police interventions and almost exactly 50% of the first aid happened during the pleasure drop), but we cannot say anything about the causality. This research demonstrates both the need for and potential of sensing what lives within a crowd in addition to the use of visitor counting sensors.