Context From June 2020 to February 2021, a consortium of 10 organisations undertook a large-scale study on open access journals across the world that are free for readers and authors, usually referred to as “OA diamond journals”. This study was commissioned by cOAlition S in order to gain a better understanding of the OA diamond landscape. Presentation The study undertook a statistical analysis of several bibliographic databases, surveyed 1,619 journals, collected 7,019 free text submissions and other data from 94 questions, and organised three focus groups with 11 journals and 10 interviews with hosting platforms. It collected 163 references in the academic literature, and inventoried 1048 journals not listed in DOAJ. The results of the study are available in the following outputs: Findings Report - DOI: 10.5281/zenodo.4558704 Recommendations Report- DOI:10.5281/zenodo.4562790 References Library - DOI: 10.5281/zenodo.4562816 Journals Inventory - DOI: 10.5281/zenodo.4562828 Dataset - DOI: 10.5281/zenodo.4553103 Zotero Library We conducted a literature search, which led us to collect 163 references, focusing more particularly on the open access business models. The literature review was used primarily to design the survey, prepare the focus groups, and analyse the answers collected. The references are stored in a Zotero library, available online.