  Diamond open access (OA) journals offer a publishing model that is free for
both authors and readers, but their lack of indexing in major bibliographic
databases presents challenges in assessing the uptake of these journals.
Furthermore, OA characteristics such as publication language and country of
publication have often been used to support the argument that OA journals are
more diverse and aim to serve a local community, but there is a current lack of
empirical evidence related to the geographical and linguistic characteristics
of OA journals. Using OpenAlex and the Directory of Open Access Journals as a
benchmark, this paper investigates the coverage of diamond and gold through
authorship and journal coverage in the Web of Science and Scopus by field,
country, and language. Results show their lower coverage in WoS and Scopus, and
the local scope of diamond OA. The share of English-only journals is
considerably higher among gold journals. High-income countries have the highest
share of authorship in every domain and type of journal, except for diamond
journals in the social sciences and humanities. Understanding the current
landscape of diamond OA indexing can aid the scholarly communications network
with advancing policy and practices towards more inclusive OA models.
