Next to open access based on author-side fees, some publishers operate on business models that do not charge authors or readers and make all content immediately available with an open license; this model is known as ‘Diamond’. They depend on institutional subsidies, library memberships, collective funding (for instance from learned societies) or voluntary contributions, and may retrieve additional income from the sale of print books.

It is not always easy to discover no-fee open access book publishers, as there are no indexing services that highlight them through filters.The following manually curated list is the most complete so far: Hopkins, K. (2026). ‘Where can I publish a book open access without (necessarily) paying a fee? A list of Diamond open access options’, Zenodo. https://doi.org/10.5281/zenodo.20287653 

• Some publishers offer a version of the book (usually HTML) for free, read-only access, but charge readers for other file formats like ePub and PDF. 

Publishers dub this model ‘freemium’, as basic content and services are free, but premium services and ease of access cost the reader or reader-side institution. If the work is made available with an open license, it is generally considered open access.