The largest DOI registration agency, Crossref has tens of thousands of members in well over a hundred countries.
These members are a part of countless different organizations, be they libraries, publishers, or research institutions to name a few. Their primary aim is to support the global research community by making millions of metadata records available for reuse. As they state, their aim is to link “research objects, entities, and actions, creating a lasting and reusable scholarly record that underpins open science.” According to their website, as of early 2026, they support two billion monthly API queries.
There are two main elements that we should understand when we talk about Crossref: digital object identifiers (or DOIs) and metadata.
What is a DOI?
Basically, a DOI is a unique string of numbers (for example, 10.xxxx/xxxxxxxx) that is used to identify where something is stored on the internet. In a way, they’re similar to a URL, but unlike regular web addresses, a DOI won’t break and present 404 errors. They’re usually on the first page of any given publication, usually in the header or footer. In the academic world, this allows work to be referenced or cited without fear of those citations “breaking” if a website goes down or someone punches in the wrong URL, as such, these are typically listed in the references section of published work.
Publishers can use a DOI to track citations, which is a very valuable tracking system. They can also associate key metadata with whatever the work in question might be. Importantly, a DOI “identifies” the object in question (here, a report or data, for example). Generally, anyone from academic institutions to governments will use DOIs for published works.
The stability of a safe place for their works is of utmost importance to many stakeholders.
At Preprints.org, each preprint would be registered with a DOI issued by Crossref, ensuring persistent identification and reliable citation. Once a DOI is assigned, authors receive an email notification. As preprints are updated, each version is given its own DOI, enabling clear tracking of research progress and supporting transparency throughout the research lifecycle.
Metadata and its uses
Unlike DOI, which has a clear and easy to understand definition, metadata can be a bit more tricky to understand. Roughly speaking, metadata is “the data that describes your data”. Different types of digital objects have different types of data. For example, if you are writing something, the metadata of that document might be “the date it was created” and/or “who the author is”. Taking a picture, however, might have metadata like “the geolocation of where the photo was taken” and/or “the model of the camera and the settings of said camera”. Depending on what you’re doing/using, the metadata will change. Sometimes, a few identifying data points will be kept, other times more.
Metadata is used for quite a few things, and one of those things is in the academic publishing world. Metadata allows academic works to be “tagged” and referenced using specific data points. For example, an author name, the subject, a specific tool used throughout the experiments, and more.
Between metadata and DOI, it is very easy to identify, track, and reference many different articles.
What is Crossref and how does it interact with preprints?
Crossref is the organization that issues persistent identifiers for academic digital content—the aforementioned DOIs. Over the years, they’ve been hard at work to create unique links to content, including journal articles and related files.
Ten years ago now, we were thrilled at the announcement that Crossrefs was developing a schema, specifically for preprints. According to their article at the time,
“Preprint DOIs would be assigned by the Crossref member responsible for the preprint and that DOI will be different from the DOI assigned by the publisher to the accepted manuscript and version of record. Crossref’s display guidelines, tools and APIs will be modified in order to enable researchers to easily identify and link to the best available version of a document (BAV). We are doing this in order to support the changing publishing models of our members and in order to clarify the scholarly citation record.”
This meant that it would be much easier to differentiate between a peer reviewed journal article and a preprint. This was especially true when it came to data mining.
Preprints allows authors to update their articles, and the Crossref schema would allow each version of a preprint to have a unique identifier (containing all the relevant metadata, including the DOI of the published article) when it becomes available.
DOIs are a great way to find and cite digital content and we are pleased that Crossref is welcoming preprints into the Crossref family.
Engaging with Preprints.org
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