The present article analyses the adoption and the main uses of the Facebook platform by three library universities in Argentina. After a bibliographic review on the topic, the methodological procedures used are showed primarily to identify the institutions that have this communication tool at present and, secondly, its uses depending on several variables, amongst them the starting moment, the links with other mass media managed by the institution (webs and social networks), the number of followers, the use of images, the frequency and the type of posts, and, finally, the quantity and the quality of the comments. In the results the obtained information is used to try to make a quantitative and a qualitative analysis of the construction of a global outlook. The conclusion shows the gradual adoption of the platform by university libraries, although with limited uses in relation to its potential. Other possibilities are suggested.