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NIH Preprint Pilot FAQs

The below FAQs are focused on the NIH Preprint Pilot and related NIH guidance, and are not intended to address more general questions about preprints.

Pilot Status

Phase 2 of the NIH Preprint Pilot launched Janaury 30, 2023. Phase 2 includes all preprints that

  1. Acknowledge direct NIH support and/or have an NIH-affiliated author; and
  2. Are posted to an eligible preprint server on January 1, 2023 or later.

With the formal launch of Phase 2, preprints that meet these criteria are being added to PMC on a weekly basis and are receiving a corresponding citation in PubMed to ensure broadest discovery and maximize the impact of NIH research.

For more information, see:

Results of Phase 1 were made publicly available as a preprint on December 13, 2022. You can read the full report in PMC or on the preprint server website.

If you have questions regarding the NIH Preprint Pilot, or if you have feedback on any aspect of the pilot for NLM, please contact

Subscribe to New in PMC for updates on the pilot and other PMC activities.

General Pilot FAQs

Why is NLM piloting the inclusion of preprints in PubMed Central (PMC)?

The primary goal of the NIH Preprint Pilot is to increase the discoverability of preprints developed with National Institutes of Health (NIH) support, maximizing the impact of the research. PMC is a widely used resource that already includes more than one million peer-reviewed author manuscripts and published articles that have been collected under the NIH Public Access Policy. NLM views the NIH Preprint Pilot as complementary to (not replacing) the NIH Public Access Policy, allowing for early NIH research results to be made publicly accessible to and more findable by the wider research community and public.

Will preprints in PMC also be reflected in PubMed?

Yes, following standard NLM practice, a citation for each preprint record in PMC is made available in PubMed to further increase the discoverability of this content.

How can I filter a PMC or PubMed search to view only preprint records or exclude preprint records?

In PMC, you can use a search filter to find preprint records: preprint[filter]. In PubMed, you can query by publication type: preprint[pt].

To exclude preprint records from your search results, you can use the Boolean "NOT" in either database, e.g., "covid 19 NOT preprint[filter]" in PMC and "covid 19 NOT preprint[pt]" in PubMed.

Additionally, for users that regularly search PubMed and want to limit their search results to the published journal literature and other documents, a search filter is now available under "Additional filters: Other" that allows you to exclude records with the publication type "Preprint" from search results.

What preprint servers are currently included in the NIH Preprint Pilot?

See Eligible Preprint Servers for complete list and information on how NLM determines preprint server eligibility.

How are updates or revisions to preprints handled in PMC and PubMed?

NLM makes every effort to get users to the most current version of an article available to them. Scripts developed by NLM staff are run weekly to identify and ingest new versions of preprints. All versions of a preprint share the same PMCID. PMC displays the most recent version of the preprint available; previous versions remain accessible through the "Other versions" link in PMC.

To connect the user to the peer-reviewed journal article version when available, NLM staff conduct additional automated checks across the following resources: bioRxiv API; Crossref API; Europe PMC RESTful API; and an NLM-developed resource, which compares the title, author lists, and abstracts of preprints with PubMed records.

Preprint records that are linked to published journal articles are labeled as "Updated" in PubMed. In PMC, links to published journal articles will display in the yellow information panel that includes all related article information.

NLM also checks weekly for withdrawn preprints and subsequently ingest the withdrawal notice. In such cases, the title of the preprint in PMC and PubMed is updated to indicate the withdrawn status. NLM staff also run daily checks for retractions of journal articles, including those that have a corresponding preprint record in PMC and PubMed.

If the pilot is discontinued, what will happen to the preprints added to PMC?

PMC will retain all preprints made available under the NIH Preprint Pilot in the archive. All public documentation will be updated to reflect that the pilot has ended.

Will preprint records be retrievable via the PMC Open Access Subset?

Preprint records with license terms that allows for more liberal redistribution and reuse will be included in the PMC Open Access Subset. These records can be identified in the in the article-meta of the XML: <article-version article-version-type="status">preprint</article version>.

Will preprint records in PubMed be retrievable via E-utilities API?

Yes, preprint records will be retrievable via E-utilities API and can be identified by the Publication Type "Preprint". You can also exclude preprint records by appending your query string with "NOT preprint[pt]" in PubMed or "NOT preprint[filter]" in PMC. E-utilities syntax requires a term before the Boolean NOT.

Does the NIH Preprint Pilot mean that multiple versions of an article may be available in PMC or PubMed?

Yes. There may be cases where PMC and PubMed include a preprint record and a subsequent record for the peer-reviewed, accepted author manuscript and/or published journal article. Preprint records will be clearly linked to later versions of the paper in PMC and PubMed, when available. The preprint record will not be removed from the archive when a later version is available.

Who should I contact if I find a preprint matched incorrectly to a published article?

Please contact if you notice any discrepancies or errors in these links.

NIH Investigators FAQs

What is the current guidance on preprints for NIH investigators?

In March 2017, NIH released guidance on "Reporting Preprints and Other Interim Research Products" (NOT-OD-17-050). This guidance includes the following instructions for authors:

Expectations of researchers: make the preprint publicly accessible, acknowledge NIH support/funding, state the work is not peer reviewed, declare any competing interests.

The guide notice also strongly encourages awardees to select a Creative Commons Attribution (CC-BY) license or dedicate their work to the public domain.

NIH awardees can link preprints to their award in My Bibliography and claim them as products of an award on a progress report publication list.

NLM encourages NIH intramural researchers who may not be able to report their preprints via My Bibliography to provide their author affiliation data at the time of submission to a preprint server and to contact if their preprint is not added to PMC and PubMed within 2 weeks of posting.

See the full guide notice for further guidance on citation of preprints and selecting preprint repositories.

If a preprint is in PMC, do I still need to submit the peer-reviewed, accepted author manuscript to comply with the NIH Public Access Policy?

Yes. Even if a preprint has been submitted to NIH as a product of award, the peer reviewed publication must be reported with the associated PMCID as proof of compliance with NIH Public Access Policy. Specifically: The requirement for publication in PMC applies only to peer-reviewed articles resulting from research supported in whole or in part with direct costs from NIH, upon acceptance for publication (NIH Grants Policy Statement, Section 8.2.2 "NIH Public Access Policy").

Preprints should not be deposited via the NIH Manuscript Submission (NIHMS) system. NIHMS is only for peer-reviewed author manuscripts that have been accepted for publication in a journal.

NIH awardees that would like to identify a preprint as NIH-supported for future inclusion in the pilot should use My Bibliography (see next question).

How can I grant permission for the full text of my preprint to be made available in PMC?

To ensure the full text of your preprint is available in PMC select a Creative Commons license [Note: NIH recommends a Creative Commons Attribution (CC-BY) license] or dedicate your work to the public domain when you submit the preprint.

The preprint should clearly acknowledge any direct NIH support.

Preprint Server FAQs

Can our organization's preprint server be added to the NIH Preprint Pilot?

We encourage you to review the Preprint Server Eligibility considerations.

What metadata need to be openly accessible in machine-readable format?

To support workflows, NLM expects preprint servers to make the following metadata openly accessible:

PMC also encourages preprint servers to collect and make available author affiliation, version, and funding metadata.

A DOI in PMC or PubMed will always link directly to the record on the preprint server site. PMC will also highlight the availability of the preprint on the server in the yellow related content box above the abstract.

PubMed supports the LinkOut service. Full-text providers can participate in LinkOut for additional prominent linking. See the LinkOut website for details.

Preprints from our preprint server are included in the pilot. How can we access usage statistics for these records in PMC?

Each preprint server with content included in the pilot will be given password-controlled access to a web site that has usage reports for preprints from their repository. The usage reports will contain the same data that PMC makes available to participating journal, as described in the PMC FAQ.

Last modified: Wed Feb. 22 2023