This chapter seeks to address the lacuna by means of Large-N comparative analysis of social media presences on Facebook and Twitter. It begins by mapping the variation of social media use across international organisation (IO) bodies and over time. Existing evidence suggests that expanding public communication in the IO organisational field is intrinsically linked to IO politicisation, that is, rising levels of public awareness and contestation of international governance. The main dependent variable counts active social media presences on Facebook or Twitter per IO body covered in the list of 290 major IO bodies provided by the Transaccess project. The analysis of social media presences run by a stratified-random-sample of IOs suggest a remarkable interest in digital communication vis-a-vis non-state audiences. The massive enhancing of social media presences by IOs concerned with such tasks suggests that social media becomes to be seen as tools for core organisational goals.