One of the fundamental aspects of online social network platforms is that they provide a number of core affordances. The actual mechanisms of these affordances vary in different platforms but their main purposes are similar: allowing users to create content and connect with each other. In this paper, we study user activity on Tumblr, we analyse user activity around the most popular posts in one year, reflecting on the effects of Tumblr’s affordances, communication style, and content discovery mechanisms on its users’ behaviour. Our findings show that the majority of user activity on Tumblr is non-verbal, users reblog and like posts but they rarely engage in conversations with others.