Our REST API makes all of the metadata we hold publicly available. It receives the majority of our API traffic, with around 1 billion hits per month. It’s one of the key ways that we fulfil our mission to make research objects easy to find, cite, link, assess, and reuse. From 1 December 2025, we will be revising the rate limits for the public and polite pools of the REST API to ensure that we can maintain a stable and reliable system, and that metadata is freely available to everyone.
Noyam Journals, based in Accra, Ghana, was recently recognised for the completeness of its metadata through the Crossref Metadata Award, part of our 25th anniversary celebrations. Noyam was one of six publishers worldwide to receive the award and stood out as a leader among members of our Global Equitable Membership (GEM) Program.
Wednesday 22nd October 2025—Crossref, the open scholarly infrastructure nonprofit, today releases an enhanced dashboard showing metadata coverage and individual organisations’ contributions to documenting the process and outputs of scientific research in the open. The tool helps research-performing, funding, and publishing organisations identify gaps in open research information, and provides supporting evidence for movements like the Barcelona Declaration for Open Research Information, which encourages more substantial commitment to stewarding and enriching the scholarly record through open metadata.
Welcome back to our series of case studies of research funders using the Grant Linking System. In this interview, I talk with Cátia Laranjeira, PTCRIS Program Manager at FCCN|FCT, Portugal’s main public funding agency, about the agency’s approach to metadata, persistent identifiers, Open Science and Open Infrastructure.
With a holistic approach to the management, production and access to information on science, FCCN|FCT’s decision to implement the Grant Linking System within their processes was not simply a technical upgrade, but a coordinated effort to continue building a strong culture of openness. With the mantra “register once, reuse always”, FCCN|FCT efforts to embrace open funding metadata was only logical.
TL;DR: We no longer charge fees for members to participate in Crossmark, and we encourage all our members to register metadata about corrections and retractions - even if you can’t yet add the Crossmark button and pop-up box to your landing pages or PDFs.
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Research doesn’t stand still; even after publication, articles can be updated with supplementary data or corrections. When research outputs are is changed in this way the publisher should report and link it, so that those accessing and citing the content know if it’s been updated, corrected or even retracted. This also emphasizes the member’s commitment to the ongoing stewardship of research outputs.
Many people find and store articles to read later, either as PDFs on their laptop or on one of any number of reference management systems - when they come back to read and cite these articles, possibly many months later, they want to know if the version they have is current or not.
Removing Crossmark fees
To encourage even wider adoption of Crossmark, and to promote best practice around better reporting of corrections and retractions, we will no longer be charging additional fees for our Crossmark service. This change applies to all Crossmark metadata registered from 1 January 2020. All members are now encouraged to add Crossmark metadata and add the Crossmark button and pop-up box to their publications - and you can do so as part of your regular content registration.
Richer metadata gives important context
We know that there are many more corrections and retractions that are not yet being registered, and to address this, we are now asking all of our members to start registering metadata for significant updates to your publications, even if you don’t implement the Crossmark button and pop-up box on your content. Remember, anyone can access the Crossmark metadata through our public REST API, and start using it straight away - even if you’re not ready to implement the Crossmark button.
Check out how to get started; if you only want to deposit metadata, follow steps one through four. If you also want to add the Crossmark button and pop-up box to your web pages/PDFs so that readers can easily see when content has changed, then also follow the rest of the steps.
Crossmark
We launched Crossmark in 2012 to raise awareness of these critical changes, by asking Crossref members to:
help readers find out about the changes by placing a Crossmark button and pop-up box (which is consistent across all members making it recognizable to readers) on your landing pages and in PDFs
Members can also use Crossmark to register additional metadata about content, giving further context and background for the reader. These metadata appear in the “More Information” section of the Crossmark box. 7 million DOIs have some additional metadata, the most common being copyright statements, publication history, and peer review methods.
Anyone can access the Crossmark metadata through our public REST API, providing a myriad of opportunities for integration with other systems, and analysis of changes to the scholarly record.
Who has implemented Crossmark?
440 Crossref members have implemented Crossmark to date. 11.4 million DOIs have some Crossmark metadata.
Total DOIs
DOIs with Crossmark metadata
%
Journal articles
80,862,460
10,155,340
12.56%
Book chapters
14,040,646
792,953
5.65%
Conference Papers
6,175,733
457,237
7.40%
Datasets
1,862,852
19,206
1.03%
Books
753,298
239
0.03%
Monographs
469,333
23
0.00%
Of those, about 130,000 contain an update:
You can see which members or journals have implemented Crossmark by viewing the relevant Crossref Participation Report.
