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Open Access

From Paywalled to OA Versions

More and more funders and universities require their authors to upload an OA version of their work to repositories. This means that, for many paywalled articles, there is also an OA version somewhere. Several (perfectly legal) tools have been developed to help readers to find them.

OA Only Tools


  • Unpaywall is an open-source and non-profit browser extension (Firefox and Chrome) that automatically searches for OA versions of articles. You can also query the database directly: enter your email address, and then you receive a report with the URL of the best OA version. 
    Unpaywall is integrated with Zotero: if Zotero cannot access the publisher's version of an article and attach it to the reference, it will use Unpaywall to find an OA version instead. 

  • The Open Access Button website allows you to search for open-access versions of articles. If it is not possible to find an OA version, it allows you to ask the author to make it available by depositing it in a repository. It is open-source, non-profit, and was launched in 2013. There are also browser extensions for Firefox and Chrome.

  • Open Access Helper allows Safari users (on desktop or mobile devices) to find OA versions of articles. There are also browser extensions for Firefox and Chrome.

Tool for OA and Paywalled Versions


  • Endnote Click is a browser extension for Firefox, Chrome, and Edge that finds the "best" (if possible, the final publication) PDF version of an article, in OA repositories or via the user's university subscription. A "locker" allows previously accessed articles to be saved.

  • Google Scholar automatically searches open access or paywalled versions of articles. 

OA Aggregators

These tools provide a search platform for open access research outputs from repositories and journals worldwide:

OA Directories