3 minute read.Co-access deprecation is coming: are you ready?
Last September, we announced we’d be deprecating co-access and encouraging its ~100 users to use our multiple resolution service. We announced that no new DOIs will be placed in co-access from 1st of July 2026 and that the ensuing 6 months should be spent cleaning up records already in co-access and moving them over to multiple resolution.
We’re here with a reminder: co-access is being deprecated…and with an update: To help with the transition to multiple resolution, we offer a tool that simplifies the process and documentation about how to set up multiple resolution.
We’re sure you have questions and we have answers:
Metadata records about books already in co-access can still be updated, until co-access is fully deprecated in January 2027.
What is multiple resolution and why should I use it instead of co-access?
Multiple resolution allows for more than one resolution URL to be registered to a single DOI. A user resolving the DOI is presented with an interim page, allowing them to choose from the various content sources registered with this DOI. Unlike co-access, multiple resolution allows for the creation of a single DOI for each item, regardless of where it might be hosted, which results in more accurate citation counts and usage statistics.
How can I migrate existing content from co-access to multiple resolution?
You and the other entities involved in the co-access relationship need to establish (or, agree on) the DOI of record to be used for that book going forward (i.e., the definitive DOI that should be shared, cited, and used on your landing pages). We propose that the DOI associated with the publisher be used as the definitive DOI for the book and its chapters. All other DOIs should be aliased to that definitive DOI (we also call definitive DOIs primary DOIs in the primary/alias relationship of duplicate DOIs).
Members with co-access DOIs can email a tab-separated list of definitive DOIs and their aliases to us for aliasing to support@crossref.org. From there, members can use our new multiple resolution tool to unlock DOIs for multiple resolution and register secondary URLs for the definitive DOIs in question. Our new tool helps with both. [You will need your Crossref credentials to login to the tool.]
Example tab-separated list of definitive DOIs and aliases
H:email=youremail@address.com;op=force_alias;delim=tab
10.5555/primarybook1 10.9876/alias1book1
10.5555/primarybook1 10.50505/alias2book1
10.5555/primarybook2 10.9876/alias1book2
What will happen if I try to register a duplicate DOI for a book that has been previously registered (i.e., the process that would have previously triggered co-access) after 1 July 2026?
Your deposit will return an error, letting you know co-access has been deprecated. The initial registration of a book will be processed free of errors (thus, the publisher with the rights to publish the book really should be the Crossref member determining and registering the book’s DOI of record). Any registration of a duplicate DOI for that same book will result in a failed submission with an error highlighting the previously registered DOI.
Have more questions that weren’t answered? We’re happy to help. Head over to our community forum to continue the conversation.
References
- Crossref (2023). Blog Publishing Process for Authors. Retrieved July 20, 2025, from https://crossref-org.turing.library.northwestern.edu/_editors/blog-publishing-process-for-authors/
- Korzec, K. & Tkaczyk, D. (2025). Meet six winners of the first ever Crossref Metadata Awards. Crossref. https://doi-org.turing.library.northwestern.edu/10.64000/xh94q-w7335
