The Covid-19 pandemic of 2020 has highlighted the need for rapid communication of research results to healthcare professionals and governments. Preprints are one way researchers can remove barriers to open science and share their findings quickly.

Since 2018, Europe PMC has made 771,807 preprints, and versions when available, searchable alongside journal published articles. If a preprint has been published in a journal indexed in Europe PMC, the preprint and published article are linked. Indexing preprints alongside journal published articles makes them more discoverable.

Preprints in Europe PMC

Similar to other articles in Europe PMC, preprints are linked to data behind the paper, can be claimed to an ORCID, included in citation networks, and linked to platforms that comment on or peer review preprints.

A preprint is a complete scientific manuscript that an author uploads on a public server for free viewing. Initially it is posted without peer review, but may acquire feedback or reviews as a preprint, and may eventually be published in a peer-reviewed journal. The posting of preprints on public servers allows almost immediate dissemination and scientific feedback early in the ‘publication’ process. Europe PMC has contributed to preprint community standards development and has hands-on expertise in publication workflows that include versions across multiple sources with diverse approaches.

If you are new to preprints, we recommend you visit ASAPbio’s FAQ page for answers to general questions on the use of preprints in scientific publishing.

Europe PMC indexes preprints from servers with publicly available content. Europe PMC has permission to download the PDF and supplementary files, and display the full text. If you have questions about how your preprint came to be included in Europe PMC, please see Preprint FAQs.

Europe PMC has two full text preprint initiatives, preprints related to Covid-19 and preprints funded by Europe PMC funders. For researchers, this means a greater number of search results can be returned when searching for content on Europe PMC. If a preprint has an open access licence, the full text will also be available for programmatic text mining enabling deeper analysis.

COVID-19 full text preprints indexed in Europe PMC

In July 2020, Europe PMC began indexing the full text of COVID-19 related preprints to make them searchable, alongside peer reviewed articles.

The COVID-19 preprints initiative was supported by a joint award from Wellcome, UK Medical Research Council (MRC), Swiss National Science Foundation (SNSF), and endorsed by the Chief Scientist of the World Health Organisation (WHO).

As the Chief Scientist of WHO I welcome the huge increase in the use of pre-prints by researchers to rapidly share the emerging evidence from the many studies on Covid-19. However, these are published as .pdf documents and I recognise that the information they contain could be more rapidly searched and linkages made between the results and data they contain if they were converted to the standard publishing language XML. I therefore support this initiative by Europe PMC to take on this task."

—Dr. Soumya Swaminathan
    Chief Scientist, WHO
    4 May 2020

This initiative was extended with a follow up award from Wellcome, UK and ended on 31 October 2023.

Europe PMC funder full text preprints indexed in Europe PMC

From April 2022 Europe PMC began indexing the full text of preprints supported by Europe PMC funders with Creative Commons licences. Similar to the COVID-19 preprints initiative, the full text is searchable and will also be available for programmatic text mining.

Preprints in Europe PMC are clearly identifiable by the green preprint label and an orange notification box which provides a warning that the article may not have been peer reviewed. If a published version of the article is available a link is provided to it. Different versions of the preprint are linked from the preprint version history. All preprints in Europe PMC are assigned a unique PPR identifier.

Preprints appearing in search results

Note that a preprints search filter is available in the left hand column. The preprint version is indicated in the green label. Only the latest version of a preprint is displayed in search results, but early versions can be found on the preprint page.

Preprint displayed within Europe PMC

Note the preprint version indicated in the green label, an orange preprint notification, and the full version history.

Currently, Europe PMC indexes metadata/abstracts from the following preprint servers:

Europe PMC considers various criteria when deciding whether to index content from a preprint server. These are as follows:

• Scope: the preprint server should contain a significant proportion of content in life science or interdisciplinary subjects
• Volume: the preprint server should have at least 30 preprints available
• Screening: the preprint server should have a screening procedure that is described in a public statement
• Access to metadata: preprint metadata should be available in a machine-readable format e.g. via an API
• Access to full text: the full text of all preprints should be visible on the preprint server with no barrier to access
• Publication ethics: the preprint server should have a public statement on its policies on plagiarism, misconduct, and competing interests

Europe PMC reserves the right to not index content from a preprint server should any of these criteria not be met.

Europe PMC requires the following metadata in a machine readable format:

• Preprint identifier (currently a Crossref DOI is required)
• Preprint title
• Author names
• Abstract
• Publication date

Desirable metadata:

• Author affiliations
• Links to peer-reviewed versions
• Licencing
• Funding
• Version information
• Withdrawal/removal status

If you are a preprint server or open research platform and interested in getting your preprints indexed by Europe PMC, please get in touch by contacting [email protected].