Every academic or university library tries its best to cater to the users to get information relevant to the users’ subject areas. To fulfill that target, academic libraries use various media to cater to their users best. The use of social media sites is one of the best ways to share knowledge with users. The present study was based on the State Universities of Sri Lanka, and it was conducted to find out first the available social media sites in academic libraries in Sri Lanka and then the most popular social media sites that used to share knowledge and information among user community in the respective university communities. There are eighteen state university in Sri Lanka. It was the population of the study. The websites of all the state universities and their faculties were selected as the sample of the study. This is a survey study and summative content analysis was used to collect data for the study. After analyzing data, it was clearly identified that Facebook was the most popular social media platform that is being used to share information about the library, programs of the library as well as the mother institute.