Published 12 July 2024

Green, gold, diamond – different models for open access books1

Open access can be achieved in a number of ways, with varying results. A publisher might make the book available open access, or an author might archive a pre-publication manuscript version in a repository for anyone to read. Other models are also explored in this article.

There are several models for open access, and a number of terms that are used to describe them. It is important to be aware of what your publisher offers and whether you must obey any funder requirements regarding which model you use to publish your work (See Business models for open access book publishing).

The two major models for open access are:

GoldImmediate open access publication in an edition created by the publisher (sometimes called the ‘Version of Record’) and made available via the publisher’s online publication platform. The book is published under a licence that permits reuse, e.g., a Creative Commons (CC) licence. In some cases, a fee (sometimes called a ‘book processing charge (BPC)’) is levied.
GreenA version of the publication, often the ‘author accepted manuscript (AAM)’, is archived online, e.g., in a repository. It does not include any of the work typically carried out by the publisher, such as copyediting, proofreading, typesetting, indexing, metadata tagging, marketing or distribution. It may not be listed on the publisher’s website. It can be freely accessed but sometimes only following an embargo period, and it may not be released under a Creative Commons licence. Green open access is also referred to as ‘self-archiving’.

There are other terms that are sometimes used to categorise open access that might be useful to know.

Diamond (also known as platinum) refers to gold open access without fees. It is typically used by publishers who are keen to emphasise that they do not charge authors to publish open access.

You might also hear the terms gratis and libre being used. Gratis is free to read but there are barriers to reuse. Libre is free to read, and the work is openly licensed (often through the use of Creative Commons licences) so that barriers to re-use are removed.

Hybrid is another label, usually applied to journals. A hybrid journal is a subscription journal in which some articles are made open access upon payment of a fee. This model has attracted particular criticism for its expense and vulnerability to abuses such as ‘double dipping’ (Boyes & Kingsley, 2016). Some book publishers offer chapter-level open access, particularly for collected and edited volumes. These are sometimes referred to as ‘hybrid books’. There are also some hybrid book series which include both open access and non-open access books within the same series.

Some people prefer other terms. For example, diamond or platinum can be referred to as ‘universal’, while green is sometimes called ‘secondary’. Instead of gold, some favour the term ‘born’ open access, and others assume that gold open access necessarily involves the payment of a fee, which is not always the case. As open access models evolve, the terminology and definitions have to keep up – for example, models in which the book is made open access via the publisher, but only after an embargo period or after a sales threshold is met, do not fit neatly into these categories.

Finally, some labels refer to works that are not open access, but might seem to be:

  • Bronze: The book is free to read and/or download on the publisher’s website, but it is not published under an open licence that permits sharing or re-use. The author does not retain the copyright. The publisher can therefore withdraw access at any time and the book cannot be freely shared elsewhere. ‘Bronze’ is often used to make content free to read for a brief period at some point after publication, but since there is no open licence it is not open access.
  • Grey: The book is shared online by an academic on their personal website or via an academic social network such as This is not open access if the book is not released under an open licence or through a Green OA route.
  • Black: This indicates a publication that is not openly licensed, or for which re-use rights have not been granted, which is shared online illegally.

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Last edited on 12 July 2024, at 11:20 (+0000)