Despite a growing number of studies featuring “informality” in their title, including many from the post-socialist region, little has been done to reach a consensus on what informality means, how to measure it and, more generally, to develop it into a widely agreed and shared theorization. Instead, and paradoxically, given that a significant number of studies rely on intuitive understandings of the phenomenon, often intended as “the opposite of formal”, this increased attention to informality has contributed to topical confusion rather than better defining what informality may be. By surveying and cross-comparing regional and world literature on informality, this article attempts to provide a coherent framework for delineating and understanding “informality studies”, outlining its main characteristics and eventually better understand its applicability and boundaries. While doing this, it calls for more attention to the political dimensions of informality and ways in which measurement of informality can be used both as a proxy for quality of governance and a deeper grasping of state–citizen relations.