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So, what is Unpaywall anyway?

Unpaywall is a service that maintains a database of links to full-text articles from open-access sources all over the world. The content is harvested from legal sources including repositories run by universities, governments, and scholarly societies, as well as open content hosted by publishers themselves. Unpaywall focuses on providing greater access to several types of open content:

  • Author-Archived Open Access content (“green OA”): Unpaywall captures OA versions of articles – generally manuscript versions – that authors have posted in repositories (while the final published versions appear in paid-access journals).
  • Hybrid OA content: Unpaywall captures individual articles which are available OA directly from the publisher, in a journal which is otherwise available only by paid subscription.
  • Full OA journal content: Unpaywall captures articles which are published in full OA journals and indexed in the Directory of Open Access Journals or other sources.

Originally called oaDOI when the associated SFX target was activated in UC-eLinks in May 2017, the service was later renamed ‘Unpaywall’. The criteria for an Unpaywall link to display on a UC-eLinks menu include:

  • A DOI is sent to UC-eLinks (via OpenURL),
  • A full-text OA version of the article is present in the Unpaywall dataset,
  • No licensed non-aggregator (commercial vendor) target exists; Unpaywall will not appear alongside licensed non-aggregator content. It may appear alongside aggregator content, such as EBSCO Academic Search Complete.

The Unpaywall target is activated in addition to other OA targets currently activated in UC-eLinks, such as DOAJ (Directory Open Access Journals Free) and BioMed Central Open Access Free, etc.

At last count in mid-2017, UC-eLinks had 42,213 free or open access titles activated. Unpaywall expands access through UC-eLinks to over 18 million OA articles.


Web of Science Integration

Starting in December 2017, Unpaywall content was integrated into the Web of Science interface. The goal is to provide Web of


Science users with access to millions of verified peer-reviewed legal versions of Gold and Green OA content.

  • For Green OA articles, Web of Science will only link to peer-reviewed versions from open repositories, NOT “pre-prints.” Two types of Green OA articles (Accepted Manuscript and Published Version) are identified.
  • For all OA articles, Web of Science will preference links to the publisher’s Gold version, when available.

According to Clarivate Analytics, the providers of the Web of Science database, “the integration of Unpaywall with the Web of Science will substantially increase discoverability and access to trusted OA content, providing a benefit to researchers and a boost to OA’s ongoing evolution.” More information is available here: