Overton is a commercial database and search platform that indexes policy documents — government publications, think tank reports, NGO and IGO publications, clinical and technical guidelines, and central bank working papers — and identifies where those documents cite academic research. It is run by Open Policy Ltd, a company founded and led by Euan Adie, who earlier founded Altmetric before it was acquired and became part of Digital Science. Overton itself is a separate company from Digital Science and Altmetric; the two products are frequently mentioned together because they share a founder and a broadly similar model — tracking mentions of research outside the traditional scholarly-citation record — not because Overton is owned by the same parent group.
For research administrators, the practical reason Overton matters is narrow and specific: it is one of the primary tools institutions use to find and evidence documented policy citations of a researcher’s or institution’s published work, which is otherwise one of the hardest categories of research impact to demonstrate systematically.
What Overton actually tracks
Overton’s core content is policy documents, not academic articles. Its own materials describe the collection as spanning tens of thousands of policy-issuing organisations across roughly 180 countries — national and regional governments, legislatures, government agencies, think tanks, NGOs, intergovernmental organisations (the WHO, World Bank, OECD and similar bodies), and central banks — and, per Overton’s published methodology, weekly-refreshed coverage. University library guides describing current Overton subscriptions (e.g. UCL’s research-metrics guide) put its scale at roughly sixteen million policy documents linked against several million academic works, though because the collection is a continuously growing, weekly-updated crawl rather than a fixed release, any specific figure is a snapshot rather than a stable number — treat coverage claims as directional, not exact.
For each policy document, Overton attempts to identify citation links to academic literature — journal articles, preprints, working papers, sometimes datasets — using automated text-mining and reference-matching methods (DOI matching, URL matching, and citation-string parsing) rather than manual curation of every link. Documents and the citation links extracted from them are searchable and filterable by document type, issuing organisation, country, policy topic, and date.
How Overton differs from a traditional citation database
This is the distinction most worth being precise about, because it’s easy to mentally file Overton alongside Scopus, Web of Science, or OpenAlex as “another citation database” when its direction of citation is inverted:
- Traditional citation databases (Scopus, Web of Science, OpenAlex, Crossref) track citations between academic works — how often a paper is cited by other papers, the basis for conventional bibliometric indicators.
- Overton tracks citations from policy documents to academic works — how often, and by which policy actors, a piece of research is cited outside the academic literature, in the documents that actually inform or accompany policy and guideline decisions.
A researcher can therefore have a modest conventional citation count and still show substantial policy citation activity in Overton, or vice versa — the two measures capture genuinely different kinds of uptake and are not expected to correlate closely. Overton is also sometimes discussed alongside altmetrics tools such as Altmetric Explorer and PlumX Metrics, which track a broader mix of online attention (news, social media, policy mentions among other signals). Overton’s policy-document coverage is deeper and more specialised than the policy-mention signal inside a general altmetrics tool, which is why institutions building an impact case frequently use Overton specifically for the policy-citation piece rather than relying on an altmetrics dashboard’s policy signal alone.
What Overton is used for
UK REF impact case studies
In the UK, Research Excellence Framework (REF) impact case studies require institutions to submit evidence-backed narratives showing how research produced a documented effect beyond academia, including effects on public policy. Overton is commonly used across three parts of that process: (1) shortlisting — comparing policy-citation counts and reach across candidate outputs to identify which have the strongest documented policy uptake worth building a full case study around; (2) narrative development — using citation data (which organisations cited the work, in how many countries, in what types of document) to establish the geographic and institutional reach of an impact claim; and (3) corroboration — identifying the specific policy organisations that cited a piece of research, which a research office can then follow up with directly for a supporting testimonial or letter. See CASRAI’s impact case study (REF) entry for how that submission requirement is structured, and the research evaluation framework guide for how REF fits alongside other national research-assessment models.
Grant and funder reporting
Outside the UK, funders that ask grantees to report on real-world outcomes — rather than only publication and citation counts — use policy-citation evidence as one input into outcomes reporting. Because Overton’s evidence is document-level (a specific policy paper citing a specific piece of research, with a URL a reader can follow), it is generally treated as more verifiable than a self-reported claim of “informed policy,” though it should still be read critically: a citation in a policy document’s reference list does not by itself establish that the research changed the policy’s substance, only that the document’s authors were aware of and referenced it.
Institutional and researcher engagement
Research offices also use Overton proactively rather than only retrospectively — to track ongoing policy engagement with an institution’s output, to identify policy-consultation or engagement opportunities relevant to a research group’s expertise, and to monitor which policy organisations are actively citing a department’s work over time, independent of any specific reporting deadline.
Reading Overton evidence with appropriate caution
A policy citation is evidence of documented awareness, not automatically evidence of causal influence. CASRAI’s policy impact entry makes this distinction explicitly: listing a policy mention from Overton without independently checking the document’s actual policy significance is a recognised misuse pattern, as is claiming legislative influence from a single, low-weight citation with no evidence the citation informed an actual decision. Good practice, echoed in the peer-reviewed literature validating Overton’s citation-linkage methodology (published in Quantitative Science Studies, MIT Press), is to treat an Overton citation as a starting point for a documented, verifiable claim — who cited it, in what kind of document, in what country — and then, where a stronger causal narrative is needed, corroborate it with additional evidence such as direct correspondence with the citing body, committee testimony records, or a documented change in guidance or practice, rather than presenting the raw citation count alone as proof of impact.
How Overton fits into the wider research-impact-evidencing landscape
Overton is one of several specialised, non-traditional evidence sources research offices now draw on alongside conventional bibliometrics:
- Altmetrics platforms (Altmetric Explorer, PlumX Metrics) track broader online attention — news coverage, social media, blogs, and policy mentions as one signal among several — rather than specialising in policy documents the way Overton does.
- SciVal, Elsevier’s Scopus-built analytics platform, draws in Overton’s policy-document data as one of several supplementary datasets (alongside patent and mass-media data) feeding its impact-analytics module, illustrating how Overton’s data is also consumed indirectly through other institutional analytics tools rather than only accessed directly.
- Conventional citation databases (Scopus, Web of Science, OpenAlex) remain the basis for academic-to-academic citation metrics and are not a substitute for policy-citation evidence — the two measure different things and are typically presented alongside each other in a case for research impact, not interchangeably.
Together, these tools reflect a broader shift in how institutions and funders evidence impact: away from citation count alone, toward a documented, source-linked narrative that can show, specifically, who outside academia engaged with a piece of research and how.
Frequently asked questions
Is Overton free to use?
No. Overton is a commercial subscription product; institutions typically license access for their research office and researchers, often through a university library or research-analytics budget, in the same way they license Scopus or Web of Science.
Does a policy citation in Overton count as formal REF evidence on its own?
Not by itself. REF impact case studies require a documented, evidenced narrative, and Overton is a tool for finding and verifying candidate evidence within that narrative — the underlying case still needs to be written up, corroborated, and submitted through an institution’s own REF process, not generated automatically from a citation count.
How is Overton different from Altmetric, given they share a founder?
Altmetric (part of Digital Science) tracks a broad range of online attention to research outputs, including a policy-mentions signal among many other sources. Overton is a separate company specialising specifically in policy-document indexing and citation extraction, with substantially deeper coverage of the policy-document space itself. The two are often used together rather than as substitutes for each other.
References
- Overton (overton.io) — company and product materials, including the Overton Index methodology page.
- Szomszor M, Adie E, ‘Overton: A bibliometric database of policy document citations’, Quantitative Science Studies 3(3), MIT Press, 2022.
- LSE Impact of Social Sciences blog, ‘How to use Overton to develop impact case studies’, 2025.
- UCL Library Services, Research Metrics guide: Overton.
