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

We recommend Lean Library over other OA browser plugins, but below is a list of some other options which you can use alongside to enhance your searching on the internet.

What Open Access plugins are available?

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.

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.


The tool is available as:

  • Browser extension for researchers and anyone interested in reading scientific documents
  • Plugin for repositories, enriching metadata only pages in repositories with links to freely available copies of the paper

Download CORE Discovery

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.

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.

Download Open Access Button


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".

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 the Library's subscriptions.

Download Unpaywall