A necessary response to a growing global population and increasing urbanisation, urban densification now has legal foundations in various countries including France and Swit- zerland, as part of the fight against urban sprawl. Although apparently simple, the reality of urban density is complex. It can be broken down into multiple indicators, none of which truly considers the human dimension, the living environment, or the experiences of residents. This article describes this complexity and presents the advantages and disadvantages of urban densification, the obstacles to its development, and the stakeholders involved. It also highlights the terminological debate between “urban density” and “urban intensifi- cation”. The latter term, preferred by some practitioners and researchers, offers a more qualitative and comprehensive approach, integrating the diversity of uses, the quality of public spaces, the place of nature in the city, and the well-being of residents. Every approach to urban intensification must be carefully planned, adapted to the local context (resources, geography, history, morphology, etc.), based on scientific knowledge regarding the effects on health, the environment, and quality of life, and involving residents from the earliest design phases. Urban intensification must address the challenge of aiming for a more resilient, inclusive, and sustainable city.