Files may seem an obvious topic for historians of public administration, but that is by no means self-evident. Despite the interest in files from sociologists and archival scientists in the early 20th century, historians have engaged more with the contents of files than with their genres, materialities and functions. After tracing the theoretical and methodological engagements with files from Max Weber and Heinrich Otto Meisner to Cornelia Vismann and Bruno Latour, we argue firstly that files are defined by their relation to other records they compile. At the same time, they transmute these documents into cases and bureaucratic objects. Secondly, just as files bring documents together, they connect the activities of individuals and organizations. However, we argue that the degree to which files are instruments of formal administrative control and organizational coherence has been exaggerated, obscuring the agency of users and the potential for files to serve other ends.