Much of the debate on Plan S seems to concentrate on how to make toll-access journals open access, taking for granted that existing open access journals are Plan S-compliant. We suspected this was not so and set out to explore this using Directory of Open Access Journals (DOAJ) metadata. We conclude that a large majority of open access journals are not Plan S-compliant, and that it is small publishers in the humanities and social sciences (HSS) not charging article processing charges (APC) that will face the largest challenge with becoming compliant. Plan S needs to give special considerations to smaller publishers and/or non-APC based journals. View Full-Text