Despite growing efforts to promote circular design in the built environment-supported by recent EU directives and digital innovation-the implementation of such strategies remains limited by a critical gap: the lack of reliable, structured, and accessible data on existing buildings. Although well-established in cultural heritage management, traditional inventory methods are not fully leveraged in the construction sector to support circularity. Furthermore, while Digital Twins offer the potential to address data-related challenges, their adoption is fragmented and hindered by the absence of standardised protocols and integration mechanisms. To address this gap, this paper examines the role of digital inventories in the built environment as valuable tools for promoting circular design in alignment with circular economy principles. It addresses the evolution of traditional inventories into advanced databases, emphasising their importance for informed decision-making, particularly in light of the European Commission's emission reduction targets for the building sector. The study defines the concept of 'digital inventory' by analysing differences and overlaps between similar concepts used in the built environment. Through a bibliometric analysis, the research systematically organises the state of the art on the topic, identifying four main clusters to group the selected documents based on their focus. Ultimately, it analyses and compares examples of platforms for circular economy. The study concludes by advocating for open, updatable digital inventories to facilitate the integration of circular design practices within the construction industry, contributing to sustainable development in the built environment.