This paper carries out a systematic and up-to-date literature review in the domain of user innovation (UI). Unlike previous reviews, this paper scrutinizes the "locus" of UI, meaning it distinguishes between studies focusing on external-to-the-firm conditions of UI (user's types, users' roles, enabling platforms, etc.) and papers focusing on internal-to-the-firm conditions of UI, such as strategies, capabilities, and organizational routines that trigger and support UI processes. This review shows that internal-to-the firm conditions represent a clearly neglected subject in the domain of UI studies. Thus, this paper encourages more research - both theoretical and empirical - to be carried out on the strategic, organizational, and managerial sides of UI.
