The Report on factors that can influence the social acceptance of the MIRROR system (D3.4) was delivered to the European Commission at the end of May 2021. The report, drafted by the K&I team composed of Luciano d’Andrea, Daniele Mezzana and Federico Marta, is the result of a process that involved three main steps: the drafting of an extensive literature review; the definition of a model of social acceptance fort the MIRROR system; its validation through the conduct of 15 interviews with representatives of border authorities, NGOs working in the field of migration, refugees, European policy makers, and experts. The report includes four parts respectively dedicated to the theoretical framework, the methodological framework, the social acceptance model of the MIRROR system and the scenarios concerning the management of the system itself.