Sometimes, book content can live in several locations as many small book publishers use multiple aggregator platforms to host their online content. This can often result in confusion over who assigns a DOI to the content on the aggregators platform, especially when the book publisher chooses not to assign their own DOI. This is where Co-access can help. This feature of our Content Registration Service allows multiple Crossref members to register content and create DOIs for the same book content; both whole titles or individual chapters.

For all Co-access registered prefixes, we’ll match DOI deposits with near identical metadata (for example, matching ISBNs and titles) and enter them into a Co-access relationship where matches are found between participating members. All deposits will initially resolve to a Co-access landing page, allowing users to select their preferred hosting location.

This means that there can be multiple DOIs registered for the same book title or chapter, and all deposits will be linked together. Ultimately this helps to give our book publisher and aggregator members greater flexibility to host content within a timeframe and in a location which suits them best.

Who is Co-access for?

Co-access is for any Crossref member who faces the challenge of assigning DOI identifiers to book content that is distributed across a number of different platforms. Crossref members who aggregate or host book content on behalf of other Crossref members can contact us to request that their prefix be added to the Co-access group for each member they work with.


Co-access enables book publishers and aggregators of book content greater flexibility to register book content with Crossref when the content is hosted on different platforms and there is no way to determine who will be the first platform to register the content with Crossref.

Why can’t book publishers and their content aggregators use Multiple Resolution to solve their distributed content needs?

Multiple Resolution works well for our journal content because each publisher is obliged to assign DOIs to their journal content, as per their Crossref membership agreement. Once the publisher assigns a DOI, any other approved aggregator is then able to add their own resolution URL into the publisher’s deposit metadata using our Multiple Resolution feature. However book publishing is different. Many of our members will in addition to publishing journal articles, also produce book content. Members are not obliged to deposit DOIs for their book titles in the same way they are for journal articles, and many prefer not to do so as they often do not host the content themselves on their own platform. Instead, book content is often provided by the publisher to a number of content aggregators who then distribute the publisher’s content across a wider online environment. Without a publisher DOI, aggregators are not able to share their hosting location information.

These aggregators and third-party platforms are often Crossref members themselves with a desire to either participate in Multiple Resolution with the publisher, or to deposit their own DOIs for book content they host in cases where the publisher chooses not the make their own deposit. Co-access therefore provides members who host content on behalf of other Crossref publishers, with the flexibility to deposit identifiers and metadata for content hosted on their own platforms, in a timeframe which suits them best.

How to register for Co-access

Prefixes must be pre-registered for Co-access in order to participate. Crossref members who host/aggregate book content on behalf of other Crossref book publisher members can register their prefix, and those of the book publishers they work with.

Before registering, aggregators should please ensure they have spoken with each book publisher they work with about Co-access deposits. Collect the following details, and then email our support team, including “Co-access” in your subject line:

  • Your Crossref membership information (i.e your prefix/s)

  • The name, prefix/s and contact details of each Crossref book publisher member you work with

  • Your company logo file, formatted according to these dimensions

  • The logo file(s) for each publisher in the Co-access group

Obligations and fees

Standard Crossref deposit fees apply. There is no additional fee to participate in Co-access.

FAQs and technical support

For more information or support, please see our comprehensive Co-access FAQs or take a look at our help documentation.

Last Updated: 2017 December 11 by Kirsty Meddings