PMC Policies

This page covers PMC’s policies related to Participation, Article Types and Content, and Article Availability and Usage.

PMC Participation

Participation guidelines

In June 2003, the PMC National Advisory Committee affirmed the policy that journals joining PMC must make the full text of their deposited content viewable in PMC, and endorsed the following participation guidelines:

  • Journals are encouraged to deposit the complete contents of each issue, not just research papers or other selected parts, in the PMC archive.
  • Journals are encouraged to provide this content to PMC as close to publication as possible, regardless of when they allow it to be publicly accessible, as this makes it easier for them to correct errors detected in the journal's files during PMC's data review process.
  • Journals are encouraged to allow their primary research articles to be viewable in PMC as early as possible but generally less than one year from publication date.
  • Journals are encouraged to allow all other journal content (e.g. letters, reviews, etc.) to be viewable in PMC as early as possible but generally less than three years from publication date.

Agreement Types

Full Participation Agreement

Full Participation participants commit to depositing the complete contents of each issue or volume of a journal, starting with a particular volume/issue or publication date in accordance with PMC’s Back Content policy.

To be eligible for inclusion under this type of agreement a journal must satisfy NLM’s Scientific and Technical quality standards for PMC journals.

NIH Portfolio Agreement

NIH Portfolio participants commit to depositing the final published version of all NIH-funded articles (as defined by the NIH Public Access Policy) from a journal, starting with a particular volume/issue or publication date. The participant may choose to also deposit additional, non-NIH-funded articles under this agreement. NIH-funded authors will be blocked from depositing manuscripts themselves from the journal via the NIH Manuscript Submission System from the starting date of deposit indicated in the agreement.

As of May 1, 2018, to be eligible for inclusion under this type of agreement a journal must be currently indexed in MEDLINE and regularly publish articles supported by NIH (or other PMC-participating or Europe PMC funders.)

Selective Deposit Agreement

Selective Deposit participants deposit a more loosely defined set of content to PMC than what full participation and NIH portfolio participants agree to. Selective Deposit is intended for the deposit of a subset of articles from a collection of journals. This model is frequently used by publishers who offer a hybrid publishing model, i.e., subscription-based journals in which selected articles are published as Open Access, or publishers who wish to support the policies of a particular funder (e.g., Wellcome Trust, Bill & Melinda Gates Foundation) which require articles to be made available in PMC under specific license terms.

As of May 1, 2018, individual articles are eligible to be deposited in PMC as part of a Selective Deposit collection if the journal of publication is currently indexed in MEDLINE or the work is funded by NIH or other funders that require deposit in compliance with their public or open access policies, such as the PMC-participating or Europe PMC funders.

Scientific, editorial, and technical standards: Reevaluation

Ongoing participation in PMC requires a journal and the journal publisher to continue to meet NLM’s quality standards for PMC and the NLM collection over time.

NLM’s criteria for accepting journals into PMC have evolved over the years. The most recent change happened in late 2014 when, with the unanimous approval of the PMC National Advisory Committee, NLM adapted its review process for PMC applicants to include an evaluation of the scientific and editorial quality of a journal by expert consultants. To maintain the quality of the archive, NLM performs ongoing review of current PMC journals for conformance with these standards.

NLM will reevaluate a journal for continued participation in PMC if there are problems identified with article(s) that a publisher fails to address or that appear to be systemic; if there are verifiable concerns about the scientific or editorial quality of the journal content; or if there are significant changes in a journal’s ownership, policies, or practices.

The reevaluation process for a PMC-participating journal is similar to the review process for new journal applications to PMC, including evaluation by external consultants. See Journal Selection for PMC for details on how journals are assessed. Before the reevaluation begins, PMC staff will notify the journal of NLM’s concerns and place a hold on processing any additional content until the review is complete. The reevaluation process will focus on recent content and may take up to 12 weeks.


A journal may be reevaluated by NLM only if it has an active PMC-participation agreement. Some articles in PMC are author manuscripts that are deposited in compliance with the public access policy of NIH or other collaborating funders and are published in journals that are not active participants in PMC.

If a journal was accepted for archiving in PMC by virtue of its inclusion in MEDLINE, the reevaluation process will involve the Literature Selection Technical Review Committee.

If, as a result of the reevaluation, the journal is found to currently meet NLM’s scientific and editorial standards for PMC, PMC will continue to accept and archive content from the journal, including all articles published during the holding period. If the journal is found to no longer meet NLM’s standards, the PMC agreement will be terminated and the journal will be eligible to re-apply two years after the date of the termination. No additional content, including any articles submitted or published during the holding period, will be accepted for archiving in PMC.

NLM’s decision to continue or cease archiving a journal in PMC is final. NLM encourages journals to use feedback resulting from the reevaluation process to improve the overall scientific and editorial quality of the journal.

NLM also looks for ongoing publisher conformance with guidelines and best practices published by professional organizations, including Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals [PDF] from ICMJE and Principles of Transparency and Best Practice in Scholarly Publishing (joint statement by COPE, DOAJ, WAME, and OASPA). If a publisher is found to not be following established industry best practices, NLM will cease collecting the publisher’s journals and not accept applications for any of the NLM Literature databases, including PMC and MEDLINE, for a minimum of three years.

PMC participating journals must continue to meet PMC’s production data requirements consistently in order to stay in PMC. If a journal does not continue to meet NLM's technical standards, NLM may terminate a journal’s participation agreement. For more information on PMC's technical quality standards see the Production Data Requirements.

Access to Electronic Resources

Participating PMC journals must remain compliant with the NLM Collection Development Manual’s requirements for access to Electronic Resources, which require electronic journals to provide NLM with complete access to the content of the journal website through one of several approved methods.

If a participating journal is found to no longer meet the access requirement, PMC will work with a journal or publisher to ensure a timely resolution to the problem. If the access issue is not resolved within six months, the journal’s PMC participation agreement will be terminated.

PMC Scope

In addition to the criteria for journals described in the NLM Collection Development Manual, NLM considers the following factors in determining if a journal is in scope for PMC:

  • The journal must be peer reviewed and have a clearly stated peer review policy.
  • The journal must publish generally within the biomedical and life sciences.
  • The primary content of the journal should consist of one or more of the following article types:
    • Original research and review articles
    • Clinical case reports
    • Data descriptor articles (Note: Articles must point to dataset that is publicly accessible.)
    • Descriptions of clinical or surgical procedures
  • The affiliations of the editors and authors should reflect the journal’s scope and demonstrate editorial independence and diversity.
  • The journal must be responsible for the peer review process and editorial processes underlying the published articles.


Journals that do not pass the initial application screening or meet PMC’s Scientific Quality Standard are eligible to reapply two years (24 months) after the date the review is completed.

Journals that do not pass PMC’s Technical Evaluation are eligible to restart the process one year (12 months) after the date the technical evaluation is completed.

An application will be closed after two years of inactivity if the journal has not completed all of the steps in the evaluation and setup process.

Any reapplication to PMC will be processed as a new application and will be subject to initial quality screening, scientific quality review, and technical evaluation (when applicable).

If a journal reapplies after previously being rejected for scientific and editorial quality, a minimum of 20 peer-reviewed articles (e.g., original research or review articles, clinical case reports) must have been published between the initial notification from PMC and the date the journal is eligible to submit a new application. If a journal has not published a minimum of 20 peer-reviewed articles by the date it is eligible to reapply, the journal should wait until the minimum has been met before submitting the new application. Please note that any content published prior to the date of the previous rejection will not be archived and is, therefore, out of scope for a PMC journal review.

Online First (OLF) articles

An Online First (OLF) article is an article version published online instead of, or in addition to, being included in an online or print issue. Other common labels for this version of an article include “ahead of print” and “early edition.” PMC generally does not accept OLF articles when they are not the final, published version of the article (version of record). An exception may be made in these cases for an article that needs to be available in PMC immediately in order to satisfy a funding agency’s policy.

Some journals consider the OLF version to be the version of record. PMC will accept OLF articles from a participant in these cases if the journal is currently indexed in MEDLINE, meets PMC’s Production Data Requirements, and successfully completes a pilot phase for OLF submission.

Journals that meet these requirements and deposit the OLF version must deposit the OLF and corresponding issue version of every article in all cases.

Back content

Participants should indicate the earliest volume/issue of the journal to be provided to PMC for archiving at the time the agreement is signed. Full-participation PMC journals that are also indexed by MEDLINE may deposit back content as far back as the earliest volume/issue indexed by MEDLINE. Generally, PMC-only (i.e., non-MEDLINE journals) may deposit content that was published up to two years prior to the date of PMC acceptance, unless the journal application was previously determined by NLM to not meet PMC standards during that period.

Language guidelines

To support the MEDLINE Policy on Indexing Electronic Journals, PMC will archive the complete contents of any MEDLINE journal that applies to PMC, regardless of language, if the journal can meet PMC’s technical standards.

For non-MEDLINE journals that apply to PMC, PMC requires the primary content to be largely in English. At this time, PMC only has the resources to review English language journals. If accepted, PMC will archive the complete contents of the journal, regardless of language.

PubMed citations

For a NIH Portfolio journal or a full participation journal with an embargo of 12 months or less, PMC will submit a citation to PubMed as soon as the article is fully processed through our system. Please note that, for any non-MEDLINE journal, only PMC can submit the journal's citations to PubMed. PMC may make an exception to this rule if a journal has no embargo. Citations usually appear in PubMed within 24 hours of submission. MEDLINE indexed journals may submit their own citations.

Publishing schedule

Ongoing participation in PMC requires a journal to demonstrate sustainability and maintain its stated publishing schedule. In cases where a participating journal repeatedly fails to keep to its publishing schedule over a 2-year period or does not publish any new content for 2 or more years, PMC will terminate the agreement for that journal. The journal may reapply if/when it resumes publishing.

Article Types and Content


For any revision to or error in an already-published article, PMC requires the submission of a published notice of correction, which should include its own complete citation information. This notice should specify the exact nature of the error, along with the citation information for the corrected article, as seen in the following:

The guidelines for submitting the correction notice are the same as for other PMC articles and should comprise an XML and PDF file, as well as any relevant image files. The XML source file must also include structured citation information about the corrected article in order to link it to the correction notice. For specific details on how the XML files should be coded, please see the PMC Tagging Guidelines.

Corrections are made available immediately in PMC without embargo.


PMC will not remove articles from its archive. However, in the event that a publisher discovers a serious problem with an article that exceeds the need for a simple correction or erratum notice, such as in cases of scientific misconduct, plagiarism, pervasive error or unsubstantiated data, then the journal must publish a notice of retraction. Retraction notices should follow NLM's MEDLINE policy on retractions and clearly state that the article is being retracted, and be published in citable form. The notice should also clearly specify the reason that the article is invalid. Please note that this policy is consistent with the standard practice of most scientific and scholarly journals and established industry best practices (e.g., ICMJE's Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals, and COPE’s Guidelines for retracting articles).

In PMC, a retracted article is marked boldly and includes a link to the retraction notice, as in this example. To create this link, the XML source for the retraction should be tagged with structured citation information about the retracted article in order to link it to the retraction notice. For an example of how the XML files should be coded, please see the PMC Tagging Guidelines.

Retractions are made available immediately in PMC without embargo.

The PMC policy on sponsored supplements is similar to the MEDLINE policy defined in Conflict of Interest Disclosure and Journal Supplements in MEDLINE.

The policy applies to journal supplements in PMC that involve any commercial sponsorship of the published research or the publication itself. In such cases, every article must include a statement clearly indicating any conflict of interest or potential influence that the commercial institution may have had on the reported findings and conclusions contained therein.

Examples of sponsored supplements to which the PMC policy applies:

  • A special issue sponsored in its entirety by an outside for-profit organization
  • A special section or group of articles whose authors have financial ties to a sponsoring for-profit organization
  • Reports from a conference sponsored by an outside for-profit organization
  • An issue or group of articles devoted to a special topic related to a proprietary product.

PMC mandates that the disclosure of conflicts of interest on the part of authors and editors must appear on each article. This statement must include the role of the sponsoring organization and any financial relationships with respect to the sponsoring group or its commercial products. The disclosure statements must appear within the article, as opposed to a blanket disclosure appearing elsewhere in the issue.

Specifically, for supplements submitted to PMC:

  • Where ALL articles are authored by employees of a commercial sponsor, the content will not be posted in the archive
  • Where the supplement has ANY commercial sponsorship, the role of the sponsor and the relationships of the authors to the sponsor are required on each article. Where no relationship exists, that should be explicitly stated on each article as well.
  • For supplements with NO outside support, each article should specifically state that the authors have nothing to disclose.

For information on XML coding of these supplements, see submission of sponsored supplements.

Supplementary Data

Any supplementary data (images, tables, video, or other documents / files) that are associated with an article must be deposited in PMC with the article. This applies to all files made available in the article record, even if the files are also available in a public repository. An exception may be made for data files that require custom software to read/use, or are very large (over 2 GB). For specific submission requirements for PMC data providers see the File Submission Specifications.

In cases where data cannot be reasonably included with an article, either in a figure, table or supplementary file, NLM encourages journals and authors to make the data available in a public repository and include the relevant data citation(s) in the paper. Guidance for PMC data providers on tagging data citations is available in the Tagging Guidelines.


The NIH Manuscript Submission (NIHMS) system can accept submissions of datasets (2 GB or smaller) in support of any manuscript files deposited in compliance with a participating funder’s public access policy. Because these datasets will be publicly accessible, those related to human subjects research should not include any personally identifiable information and deposit should be consistent with informed consent. For more information on depositing supplementary data and dataset files via NIHMS, see the related NIHMS FAQ.

Article Availability and Use


Journals may choose to set a default embargo period during which articles that have been received by PMC will not be freely available in full text on the PMC website. The maximum embargo is typically 12 months after publication. A request for a longer embargo will require approval from NLM. Please note: Embargoes longer than 12 months will impact the timing of citations for articles appearing in PubMed: if a journal has an embargo longer than 12 months, PMC will not submit a citation to PubMed until the article has cleared its embargo.

Information about the default embargo or release delay for each journal in PMC can be found under the “Free Access” column on the PMC Journal List and the exact release date for each article under embargo can be found on the table of contents for the issue in which the article appears or in the corresponding PubMed record.

The default embargo is typically set automatically at the journal level, however it is possible to override the default embargo for a specific article using a processing instruction (PI) in the XML. See the PMC Tagging Guidelines Processing Instructions section.

Restrictions on systematic downloading of articles

Crawlers and other automated processes may NOT be used to systematically retrieve batches of articles from the PMC web site. Bulk downloading of articles from the main PMC web site, in any way, is prohibited because of copyright restrictions.

PMC has two auxiliary services that may be used for automated retrieval and downloading of a special subset of articles from the PMC archive. These two services, the PMC OAI service and the PMC FTP service, are the only services that may be used for automated downloading of articles in PMC. See the PMC Open Access Subset for information about which articles are included in this special subset, and for links to the PMC OAI and FTP services. Do not use any other automated processes for bulk downloading, even if you are only retrieving articles from the PMC Open Access Subset.

Articles that are available through the PMC OAI and FTP services are still protected by copyright but are distributed under a Creative Commons or similar license that generally allows more liberal use than a traditional copyrighted work. Please refer to the license statement in each article for specific terms of use. The license terms are not identical for all the articles.

PMC will consider adding external links in reference lists to aid users in discovering and accessing content cited in PMC articles if all the following criteria are met:

  • Links must be of potential use to NCBI/NLM database users. Useful links will expand upon information already found in PMC.
  • Link provider has been widely adopted by major scientific publishers and platforms.
  • Link provider prioritizes discovery of the publisher’s full-text as the version of record.
  • Link provider responds to complaints regarding copyright infringement and complies with the PMC Copyright Notice.
  • Links should deliver the relevant information to users with few or no intermediary steps.
  • Inclusion of links should not unnecessarily overburden NCBI resources.

PMC can only include external links in reference citations that are to the reference source, not to related content.

The label of the link in the PMC display will be that of the link provider.

PMC is a service of the National Library of Medicine, a Federal agency, and as such it is produced using Federal computer and network facilities. Because these types of public facilities cannot be used for private commercial advertisement, endorsement, or competition, special care must be taken by resource providers with a commercial interest in linking from PMC. Resource providers should not attempt to use PMC as a form of advertising. Resource providers found willfully disregarding these guidelines will be barred from further inclusion in PMC.

See also the PMC Disclaimer for information on Endorsement and External Links.

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Last updated: Tuesday, 11 Sept 2018