Crossref was created back in 2000 by 12 forward-thinking scholarly publishers from North America and Europe, and by 2002, these members had registered 4 million DOI records. At the time of writing, we have over 23,600 members in 164 different countries. Half of our members are based in Asia, and 35% are universities or scholar-led. These members have registered over 176 million open metadata records with DOIs (as of today). What a difference 25 years makes!
In our 25th anniversary year, I thought it would be time to take a look at how we got here. And so—hold tight—we’re going to go on an adventure through space and time1, stopping every 5 years through Crossref history to check in on our members. And we’re going to see some really interesting changes over the years.
The Frankfurt Book Fair is the largest book fair in the world, and therefore a key event on our calendar. Held annually in Frankfurt, Germany, the 77th Frankfurt Book Fair (October 15–19, 2025) saw 118,000 trade visitors and 120,000 private visitors from 131 countries. The Crossref booth was located, as usual, in Hall 4.0 where all the stands with information about academic publishing can be found. Four Crossref colleagues attended the Book Fair this year, and in this blog post, you can read more about their meetings, experiences, and plans.
TL;DR. Metadata Manager will be retired at the end of 2025. Over the past four years, we have been developing a new helper tool to replace it, and that tool has now reached a stage of maturity that means we will be able to switch off Metadata Manager by the end of the year.
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.
Reference linking enables researchers to follow a link from the reference list to other full-text documents, helping them to make connections and discover new things.
Reference Linking means including Crossref DOIs (displayed as URLs) in the reference lists that you provide in your own published work. This enables researchers to follow a link from a reference list to the current landing page for that referenced work. And because it’s a DOI rather than just a link, it will remain persistent.
So, instead of just including the reference in your reference list…
Soleimani N, Mohabati Mobarez A, Farhangi B. Cloning, expression and purification flagellar sheath adhesion of Helicobacter pylori in Escherichia coli host as a vaccination target. Clin Exp Vaccine Res. 2016 Jan;5(1):19-25.
…you should also display the DOI link:
Soleimani N, Mohabati Mobarez A, Farhangi B. Cloning, expression and purification flagellar sheath adhesion of Helicobacter pylori in Escherichia coli host as a vaccination target. Clin Exp Vaccine Res. 2016 Jan;5(1):19-25. https://doi-org.turing.library.northwestern.edu/10.7774/cevr.2016.5.1.19
Because Crossref is all about rallying the scholarly community to work together, reference linking is an obligation for all Crossref members. But you don’t have to be a Crossref member to link your references - we provide free tools that anyone can use to match their reference lists to existing DOIs so they can link their references.
Watch the introductory reference linking animation in your language:
Persistent links enhance scholarly communications. Reference linking offers important benefits:
Reciprocity: members’ records are linked together and more discoverable because all members link their references.
As a member organisation, we can obligate all our members to link their references, so that individual members can avoid the inconvenience of signing bilateral agreements to link to persistent resources on other platforms. The result is a scholarly communications infrastructure that enables the exchange of ideas and knowledge.
Discoverability: research travels further when everyone links their references. Because DOIs don’t break if implemented correctly, they will always lead readers to the resource they’re looking for, including yours. When the DOIs are displayed, anyone can copy and share them. This will also enable better tracking of where and when people are talking about and sharing scholarly objects, including in social media.
Obligations and fees for reference linking
Reference Linking is an obligation of membership for all Crossref members. But anyone can use our support tools for Reference Linking - you don’t have to be a member. And there’s no charge to use our support tools for Reference Linking.
Getting started with reference linking
There are various different ways to look up other member’s DOIs to add to your reference lists. Read more here.
