Twitter is used as an example of a distinctively digital institution. Twitter’s constitution and development is a test case for Searle’s theory of Status Function Declarations. The analysis distinguishes between acts of the individual members of Twitter, joining, following and tweeting; and the acts, or Status Function Declarations of the Twitter system as a whole, manifested in the way that the software system can change, and the way in which Twitter can interact with other institutions through its Application Programming Interface. It is argued that Twitter is an exemplar or paradigm and not an exception. All our very new digital institutions use language in ways quite different from traditional institutions and in understanding digital institutions we need to probe the basic actions, the Status Function Declarations through which we build and shape their performance and evolution. It is further suggested that the normative structures we find in digital institutions arise directly from the Status Function Declarations of their members and this insight helps us understand how they attract and may magnify problematic behaviour — in the case of Twitter, trolling and bullying. The theory of digital institutions developed is naturalistic and evolutionary and the work of Michael Tomasello on primate behavior and child development has suggestive parallels for understanding the development of social media.