The Crossref Curriculum

Posted content (includes preprints)

Posted content includes preprints, eprints, working papers, reports, dissertations, and many other types of content that has been posted but not formally published. Note that accepted manuscripts are not considered posted content.

To qualify as posted content, an item must be posted to a host platform where it will receive some level of stewardship. We’re all about persistence, so it’s vital that everything registered with us be maintained.

Our members asked for the flexibility to register content at different points in the publishing lifecycle, so we extended our infrastructure to support members who want to register preprints.

Our custom support for preprints ensures that links to these publications persist over time; that they are connected to the full history of the shared research results; and that the citation record is clear and up-to-date.

Publishing preprints is about more than simply getting a DOI

We have designed a schema together with a working group that included preprint advisors bioRxiv and arXiv, along with some members including PLOS, Elsevier, AIP, IOP, ACM. The schema lays out what metadata is specifically important for preprint content. We also developed a notification feature to alert preprint creators of any matches with journal articles, so they can link to future versions from the preprint.

It’s important to clearly label the content as a preprint using a preprint-specific schema. It’s not advisable to register preprints as data, components, articles, or anything else, because a preprint is not any of those things. Our service allows you to ensure the relationships between preprints and any eventual article are asserted in the metadata, and accurately readable by both humans and machines.

Since November 2016, members have been registering tens of thousands of preprints with us, and thousands of those in turn already have matches with journal articles too (requires a JSON viewer). These relationships in the Crossref metadata, available through our APIs, are relied upon by many parties - from researchers to funders - to discover, track and evaluate the preprint journey.

Benefits of our custom support for preprints

  • Persistent identifiers for preprints to ensure successful links to the scholarly record over the course of time
  • The preprint-specific metadata we ask for reflects researcher workflows from preprint to formal publication
  • Notification of links between preprints and formal publications that may follow (such as journal articles, monographs)
  • Reference linking for preprints, connecting up the scholarly record to associated literature
  • Auto-update of ORCID records to ensure that preprint contributors are acknowledged for their work
  • Preprints include funding data so people can report research contributions based on funder and grant identification
  • Discoverability: we make the metadata available for machine and human access, across multiple interfaces (including our REST API, OAI-PMH, and Metadata Search.

Obligations and limitations for depositing preprints

Members depositing preprints need to make sure they:

  1. Register content using the posted content metadata schema (see examples below)
  2. Respond to our match notifications that an accepted manuscript (AM) or version of record (VOR) has been registered, and link to that within seven days. You should designate a specific contact with us who will receive these alerts (it can be your existing technical contact)
  3. Clearly label the manuscript as a preprint, above the fold on the preprint landing page, and ensure that any link to the AAM orVOR is also prominently displayed above the fold.

Other considerations:

  • References will be flagged as belonging to a preprint in our Cited-by service
  • The preprint is treated as one item only without components for its constituent parts
  • Each version should be assigned a new DOI, and associate the versions via a relationship with type isVersionOf - learn more about structural metadata and declaring relationship types
  • Preprints are not currently able to participate in Crossmark.

Membership and fees for depositing preprints

Preprint creators who would like to use our preprint service should apply to join as a member. We have a dedicated fee structure for registering each preprint, and volume discounts offered for both backfile and current content. Learn more about our fees.

Are you an existing Crossref member who wants to assign preprint DOIs? Let’s talk about getting started or migrating any existing mis-labelled content over to the dedicated preprint deposit schema. You can also give us a specific contact who will receive match notifications that an author’s accepted manuscript or version of record (AAM or VOR) has been registered. If you’re not yet a member but want to register your preprints so they are included within Crossref infrastructure service, please contact us so we can answer any questions and get you set up.

Associating posted content with published content

Once a content item has been published from the posted content and a DOI has been assigned to it, the posted content publisher will update their metadata to associate the posted content with the DOI of the accepted manuscript (AM) or version of record (VOR).

We will notify the member who deposited metadata for the posted content when we find a match between the title and first author of two publications, so that the potential relationship can be reviewed. The posted content publisher must then update the preprint metadata record by declaring the AM/VOR relationship. The notification is delivered by email to the technical contact on file. Please contact us if you need the email notifications to be sent to a different address.

Displaying and labeling on posted content publications

You must make it clear that posted content is unpublished and you must ensure that any link to the AM/VOR is prominently displayed, specifically:

  • The landing page (or equivalent) of the preprint must be labeled as not formally published (for example, preprint, unpublished manuscript). This label must appear above the fold (the part of a web page that is visible in a browser window when the page first loads)
  • The landing page (or equivalent) of the preprint must link to the AM/VOR when it is made available. The link must be appropriately labeled (for example, Now published in [Journal Name], Version of record available in [Journal Name]) and appear above the fold.

Depositing and updating posted content

Posted content is a Crossref content type available starting with schema version 4.4.0. The schema updates include a number of posted content-specific elements. The top level element is called posted_content and has an attribute called type. This attribute is given a value from an enumerated list that defines the nature of the posted content. The current set of enumerations are:

  • preprint
  • working_paper
  • letter
  • dissertation
  • report
  • other

The default value is preprint. Please contact us if you want to deposit metadata for a posted content type which is not on this list.

Metadata elements

The posted content type contains the following elements (* = required):

Element Description
group_title* The hosting platform may organize its posted content into categories or subject areas. This field is used to name the container for the posted item
contributors* Container for author information
titles* The titles (title and subtitle) of the posted content
posted_date* The date when the posted content became available online on the hosting platform
acceptance_date The date the content item was submitted to and accepted by the hosting platform
institution Container for information about an organization that sponsored or hosted an item but is not the publisher
program: funding Source of funding applicable to research related to the posted content
program: access indicators License terms
program: relations Relationships (other than bibliographic citation) to other works, such as found in acknowledgments or list of supplemental material
doi_data* Container for persistent identifier and URL
citation_list Posted content bibliography listing of citations to other works

Updating metadata with relationship to AAM/VoR

Once a posted content item has been published, the posted content publisher must update their publication metadata with the AAM/VoR DOI using the isPreprintOf relation type.

<program xmlns="">
         <!--DOI of the AM / VOR-->
         <intra_work_relation relationship-type="isPreprintOf" identifier-type="doi">10.5555/preprint_sample_doi_vor</intra_work_relation>

The relationship metadata may be updated with either a full metadata deposit (existing metadata plus the ‘relationship’ metadata) or as a resource-only deposit. Metadata deposited using the resource schema will be appended to the existing metadata.

Posted content and conflicts

When a posted content item is submitted for a published item that has a registered metadata record, a conflict is created. The conflict is resolved when the posted content item is updated with the relationship metadata for the published item’s DOI. Learn more about the conflict report.

Posted content and Cited-by matches

When you query for Cited-by matches, you can choose to include posted content matches in your results. By default, posted content is not included. To retrieve matches including posted content:

HTTPS queries

Add the include_postedcontent=true parameter to your query, for example:

XML queries

Add the include_postedcontent="true" attribute to your fl_query element, for example:

<?xml version = "1.0" encoding="UTF-8"?>
  <query_batch version="2.0" xmlns = "" xmlns:xsi="">
    <head><doi_batch_id>eXtyles Request AMP.dodge0724.doc__76</doi_batch_id>
    <fl_query include_postedcontent="true"><doi>10.5555/12345678</doi></fl_query>

Example of a posted content deposit

Review the sample below or download an XML file.

       	<!--group_title: Prepublication content items may be organized into groupings within a given publisher. This element provides for naming the group. It is expected that publishers will have a small number of groups each of which reflect a topic or subject area. (required)--> 	 
       	<group_title>Metadata Quality</group_title>
           	<person_name sequence="first" contributor_role="author">
           	<title>Mind your &lt; and &gt;: why XML needs to be valid</title>
       	<!--posted_date: The date when the posted content became available online on the hosting platform (required)-->
       	<!--acceptance_date: date the content item was submitted to and accepted by the hosting platform. (optional) -->
       	<!--optional funding and license data-->
       	<program name="fundref" xmlns="">
           	<assertion name="fundgroup">
               	<assertion name="funder_name"> U.S. Department of Energy <assertion
               	<assertion name="award_number">DE-FG03-03SF22691</assertion>
           	<assertion name="fundgroup">
               	<assertion name="funder_name"> U.S. Department of Energy <assertion
               	<assertion name="award_number">DE-AC52-06NA27279</assertion>
       	<program xmlns="">
           	<free_to_read start_date="2016-01-01"/>
       	<!--DOI and URL (required)-->
       	<!--citation list for the item (optional)-->
           	<citation key="pp1">

Example of a posted content deposit containing a relationship to a VOR

Review the sample below or download an XML file.

<!-- relationship established with VOR DOI (required when VOR is identified)-->
    <program xmlns="">
          <intra_work_relation relationship-type="isPreprintOf" identifier-type="doi">10.5555/preprint_sample_doi_vor</intra_work_relation>
           <!--DOI and URL (required)-->

Example of a journal article deposit that includes a relationship to posted content

Review the sample below or download an XML file.

<!--relationship established with posted content (preprint) DOI-->
<program xmlns="">
     <intra_work_relation relationship-type="hasPreprint" identifier-type="doi">10.50505/preprint_sample_doi_1</intra_work_relation>

Example of email notification of posted content match

Member Example Publishing has deposited DOI 10.5555/preprint_sample_doi_vor ( claiming it is the VoR for your posted content DOI 10.50505/preprint_sample_doi_1. Please display a link to the Version of Record from your posted content online. Linking posted content to the published record is critical to enabling the full history of scholarly results, and ensuring that the citation record is clear and up-to-date. If you have questions please contact and one of our colleagues (in the EST timezone) will get back to you. Many thanks, Crossref

Last Updated: 2020 April 8 by Amanda Bartell