Civic technologies emerged a few years ago as tools to create new dynamics in the management and governance of urban planning, as well as renewing participatory democracy. In territories where the collision of different scales complicates the understanding, governance and transformation of the built environment, approaching citizen participation through these tools appears as an innovative approach. This research analyses the challenges of integrating online platforms (or mobile apps) into citizen participation tools in the field of urban planning. Its main objective is to understand how and to what extent these tools are likely to transform the mechanisms of public participation. It is currently accepted that online platforms can overcome some of the limitations of offline participatory mechanisms. However they also create new ones. To address this issue, the research is based on (1) a survey, the "Civic Tech Barometer", carried out among public authorities in Switzerland to understand their uses and practices in terms of civic technologies, (2) a case studies, the observation of (changes in) practices with regards to citizen participation within the urban planning administration in the Canton of Geneva and the analysis of two participatory projects including online citizen participation platforms, (3) the analysis of the Decidim tool and its appropriation by public authorities. The thesis addresses processes of urban planning and the production of the city in the light of the integration of civic tech. The aim is to understand whether the integration of civic tech in urban planning participatory projects transforms the practices of public authorities and/or whether it feeds a new imaginary of citizen participation.