To explore the affordances and transformative dimensions of social media use in formal and informal learning contexts in higher education, a review of research literature was undertaken following general methodology for systematic reviews and meta-analyses. A convenience sample of 150 studies was drawn from the 954 sources identified, and reviewed for descriptive theme, learning environment, formal/informal learning context, user types, social media tools, user aggregations, study design and outcomes. Descriptive statistics are presented. Thematic analysis yielded three transformative dimensions of social media use – emergent, administrative and process – which are described and mapped across diverse learning contexts. Grounded in actor-network theory, transactional distance theory and the Community of Inquiry framework, a conceptual model is proposed repositioning tools as primary actors relative to learners (users) and content, adding user<->tool<->content<-> interactions that take place within a common cognitive plane. This model re-envisions the mutually shaping relationships amongst these three primary actors, contextually embedded within digitally connected environments. Three roles – learner, facilitator, contributor – that users occupy fluidly in learning activities incorporating social media are described. Drawing on these analyses, some basic best practices for social media integration are suggested.