OAPEN promotes and supports the transition to open access for academic books. It was first an EU co-funded project and now continues as a foundation supported by leading Dutch libraries.

OAPEN operates three platforms:

OAPEN Library – a central repository for hosting and disseminating OA books
OAPEN Open Access Books Toolkit – a toolkit on OA book publishing for authors
Directory of Open Access Books – a discovery service indexing OA books, in partnership with OpenEdition