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A third to a half of articles have an OA version, but finding them can be a challenge. Save time with these easy-to-install OA discovery tools that search repositories, preprint servers, etc. for you

Click on name of each OA plugin to link to the web page where you can download it. You may find this handy table guide helpful.

Lean Library - *Recommended*

We recommend Lean Library over other OA browser plugins.

Lean Library delivers to your desktop the article or chapter you want seamlessly if Cambridge University Libraries provide subscription access, regardless where you are accessing from (on or off campus).

Lean Library finds and delivers an OA version of the article or chapter if there is no subscription access.

In the last resort (no subscription and no OA version) Lean Library triggers an Inter Library Loan form so you can place an order and have the article emailed to you.

+ Download Lean Library
How does it work?

Once installed in your browser, Lean Library links you automatically to your article via your IP and via subscription access or, if that's not available, to an Open Access version if you are on campus or, if you are off campus, Lean links you via the University Library's server (EZproxy) for subscription access or to an OA version. Lean Library uses the Unpaywall database to check for an OA version. Installing the plugin is very straightforward - Please visit this page:

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Other browser plugins will find OA versions of articles, but will not integrate with subscribed journals and online resources that the libraries provide.  Cambridge University Libraries view Lean Library as an important tool to provide for members of the University as we believe it significantly improves the efficiency of finding and getting access to online content that is needed for teaching and research.

CORE Discovery

CORE Discovery finds Open Access copies of articles, using the CORE dataset of millions of full text OA papers, as well as the data of other providers.

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CORE Discovery arguably has an edge on other extensions because it is backed by the CORE data and the CORE services' lead in harvesting OA literature.

CORE Discovery claims to have "the best grip on open content from open repositories as opposed to other services that disproportionately focus only on content indexed in major commercial databases."

CORE Discovery also claims to be the only discovery system that can locate scientific content even for items with an unknown DOI or which do not have a DOI.

Open Access Button

Open Access Button searches thousands of sources containing millions of articles to connect you to an article instantly if it is freely available. The Button now comes from OA Works

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The Open Access Button also provides a service of requesting an article from the author if you don't have access via subscription and the article isn't yet OA. Open Access Button helps authors to make their article OA and supports the growth of research available in the public domain by enabling the process in this way.


The Unpaywall plugin searches the Unpaywall database which works by harvesting from Open Access sources to find OA content and then matching that content to the Crossref DOI, so for any DOI searched via the plugin, Unpaywall "knows about any OA versions that exist anywhere".   

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The Unpaywall extension is already integrated into many search and discovery tools and platforms, including Lean Library, OCLC, Scopus, Web of Science, and Dimensions.

You may add the plugin to your browser in addition, but if you have installed Lean Library, you will already be searching Unpaywall's database because Lean Library searches Unpaywall when access is not available via Cambridge University Libraries subscriptions. 


Kopernio provides a link via a Kopernio "View PDF" pop-up icon in your browser to the "best available full-text PDF" of an article and works in the same way as other extensions, by searching for a OA version on open databases on the Internet.

A guide to getting the most out of Kopernio and setting up your connection to possible subscription access to the PDF you need, before Kopernio delivers an OA version, is available here.

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One of Kopernio's distinctive features is that it is integrated with Web of Science as Kopernio is produced by Clarivate Analytics. This is an advantage if you are a WoS user.

A guide to Kopernio's advantages highlights the "Kopernio Locker" which saves your search history for easy retrieval of articles at any point in time.  You can upgrade to Kopernio Premium by sending a referral link to a colleague (this will give you 2GB of Locker storage, integrate seamlessly with Dropbox, apply tags, and export to your reference manager).

Cambridge has connected with Kopernio to enable the extension to link to Cambridge's server for off campus access, so when you are away from Cambridge you can use the extension to link to any access you have as a member of the University via Cambridge University Libraries' subscriptions.

Note that this connection is a "dumb" link and is going to attempt a connection to the off campus server regardless of whether or not Cambridge has subscription access available to you; it is also not connected to the updates to the server which are made every week. By contrast Lean Library is "sensitive" to the availability of subscription access and will only link to that when it is available; Lean is also updated every 24 hours with any changes made to the server for off campus access.

Read by QxMD

Read by QxMD is designed for medical researchers and professionals in mind, and is an App for mobile devices that has the mission to facilitate "the process by which new knowledge is incorporated into clinical practice".  

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Read does this by connecting you to papers that are relevant and newly published in your area, which you can pre-select by journal, collection, or keyword.

Cambridge has worked with QxMD to integrate Read with journals subscribed by Cambridge University Libraries. When you create your Read account select "University of Cambridge" from the dropdown of institutions to pick up the connection to subscription journals in medical and life sciences on or off campus. Read will also connect you to an Open Access paper if subscription access isn't available and an OA version exists in the data sources Read searches.

Visit QxMD to create an account and start enjoying the benefits.

Google Scholar Button

Adding the GS button to your browser lets you check GS quickly from any article page to see if you may have subscription access or another Open Access version may be available.

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The Google Scholar button can be added to your browser from the Chrome Web Store. Once installed you can click on the GS button which will open a popup box providing links to different versions of the article and the citation for the article in different referencing styles.

The popup gives you a link to the subscription version of the article if it is available via Cambridge University Libraries subscriptions.

To display the link to Cambridge University Libraries, you first need to select "University of Cambridge - ejournals@cambridge" by searching for Cambridge in the "Library links" section of account settings on Google Scholar.

Cambridge University Library publishes all the details of its subscriptions (journals, articles, volumes, etc.) to Google Scholar each week. Although this keeps GS up to date and the links you see should be correct, our experience is that the links against articles in GS do not always correctly reflect entitlements to access, so there is a certain unreliability in the metadata in GS.

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