This doctoral research was completed over a long period of time (2010-2022) and is positioned between the world of museums and the information and communication sciences. The start of this research (October 2010) corresponds to a period when museums began to register in larger numbers on Facebook and Twitter. At the same time, the information and communication sciences were revisiting the concepts of audiences, communities or participation, in light of the Internet and social network sites. Surveys on museum practices show that access to museums is strongly linked to socio-economic criteria, particularly the education level of visitors. Museums have tried and are still trying to reduce these inequalities of access thanks to various mediation tools, including their Facebook and Twitter accounts. Do these social network sites renew the relationship between museums and audiences, do they make it possible to go beyond this relationship of access, do we find more traces of interaction, or even participation? To answer this question, which is the main theme of this doctoral research, we chose to focus on the uses of Facebook and Twitter by museums that are less studied than the so-called superstar museums such as the Musée du Louvre or the British Museum. The four museums that provide the basis for this research are located in Belgium (Musée royal de Mariemont and Museum aan de Stroom) and in the Grand Duchy of Luxembourg (Musée national d’histoire et d’art and Mudam). First, a content analysis was carried out on data extracted from the Facebook and Twitter accounts of the four museums, which covers one year of uses (2011-2012). This analysis was useful on two levels. The first is methodological. Despite the small amount of data (1998 tweets, 328 posts and 679 Facebook comments), it corresponds with issues related to Big Data, particularly the ethical questions of data extraction and the choices made in delimiting the corpus of the analysis, which can have important consequences on the results. The second level ...