This is the data publication of a research project entitled "The Tragedy of the Cultural Commons", conducted at the Centre for Digitalization Research (CAIS, Bochum) within a Fellowship (October 2021 - March 2022). The data publication consists of a) a research report (in pdf format), b) redacted transcripts of interviews conducted during the fellowship (14 UTF-8 encoded txt-files), and c) the export of the codes used for the analysis of the interviews (47 UTF-8 encoded, comma-separated csv-files). The research report provides core insights achieved during a research project which examined cultural heritage that has been digitized by European cultural heritage institutions as a commons, i.e. as a shared resource that is managed by a community. The first part of the research report systematically analyses the digital assets of a range of European cultural heritage institutions within a cultural commons framework. The results presented in this section are arranged with regard to the background environment of the commons, the characteristics of the resource and its governance, as well as typical patterns and outcomes, and they are mainly based on interviews with cultural heritage practitioners conducted during the fellowship. The second part of this report goes deeper into some of the issues arising with the availability of large amounts of digital cultural heritage, issues that have not been anticipated when digital transformation of cultural heritage began around the turn of the millennium, and which are related to the switch from the analogue to the digital. Firstly, one of the tasks of cultural heritage is to update cultural contents by creating culture anew. While this task is generally enabled and enhanced by the broad range of digital assets which are in the public domain and available in open access, intellectual property rights often form a barrier for the access to born-digital content and content which has been produced in the 20th century. This rights regime conflicts with the cultural practices established in communities in the creative sector working with digital material and with their expectations regarding the open accessibility of such digital assets. Secondly, the conversion of cultural heritage from analogue to digital has furthered its commodification. The availability of digital cultural heritage as Big Data Large pronounced its economic value and opened up previously unknown possibilities for exploitation. Large textual databases created out of digitized cultural heritage may serve as a foundation for machine learning applications and thus may feed machine translation services or support the establishment of large language models; or large image databases, enriched with crowd-sourced annotations, may support and enhance computer vision and a deepened understanding of such material by machines. From the viewpoint of a commons, the issue lies with the potential exploitation of these digital assets by private companies and thus in loss of communal benefits due to actions motivated by self-interest. This situation is termed the “Tragedy of the Cultural Commons”. Such a tragedy can be mitigated by cultural heritage institutions developing secondary products out of their digital assets on their own, like establishing machine learning models, providing parallel corpora for machine translation, establishing large language models for text generation etc. and by providing their users as well as companies with a licensed access to these models or products.