Unpaywall: read research papers legally for free

Martin Brinkmann
Apr 18, 2017

Unpaywall is a free browser extension for Firefox and Chrome that allows you to read research papers behind paywalls for free legally.

The extension works identical in both browsers. Whenever you hit a research paper paywall on the web that asks you to pay up to read the whole paper, a query is run in the background to check whether a copy of the research paper is already available in a free index.

If that is the case, that is indicated to you in the browser. All it takes then is to click on an icon in the browser to read the paper for free, legally,

The maintainers state that the index has over 10 million entries already, and that the system finds fulltext for 65% to 85% of research articles. The service relies on several databases and data sources such as PubMed Central, the DOAJ, Google Scholar or BASE, and that all these are made available via an API.


Unpaywall is not the first service that you may use to find free copies of research papers that are locked behind a payway. The OA Button extension for Chrome comes closest probably. While it handles things a bit different -- you click on the extension's icon to run a search, and may use a couple of extra features such as a search form on the project website or requests -- it runs similar queries in the background.

Unpaywall is more hands-off as it runs the scan for a free copy of a research paper automatically, but it lacks the advanced features that OA Button offers.

The browser extension ships with two options thought that you can enable on the preferences page. Click on the extension icon and select settings to open the preferences.

  1. Color-code tab for green and gold OA -- This setting, when enabled, color codes the lock icon to distinguish between articles that are made available by the publisher under an open license (gold), and articles available on an institutional repository or preprint server (green).
  2. Hide content from less trusted sources -- Filters some resources so that they are not queried when searches are run.

Unpaywall does not store or ask for personal information, or tracks the browsing history. You find the privacy policy and frequently asked questions on the official website.

Closing Words

If you read research papers, either because you are in academia, a student, or interested in the subject, then you may like what the browser extension has to offer. Its growing index of research paper copies provides you with free legal access to articles behind paywalls.

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  1. Clairvaux said on April 18, 2017 at 10:30 pm

    Great idea.

  2. Tom Hawack said on April 18, 2017 at 12:23 pm

    Thanks for the post Martin.
    Unfortunately “Unpaywall is more hands-off as it runs the scan for a free copy of a research paper automatically” and I really dislike add-ons operating automatically in the background when the databse is not local, hence sending all visited pages’ urls to a whatever server. Why not let the user ask/click the add-on when he chooses to? Not complicated. Even if a server is as honest as it can be I just avoid being followed when I have the choice. Users are already sufficiently tracked against their will to not add deliberate user chosen tracking, be it “following”.

    Moreover I just noticed that the Unpaywall’s home page includes a call to the user’s localhost to run a script called livereload.js (http://localhost:35727/livereload.js). Never encountered this call before.

  3. Henk van Setten said on April 18, 2017 at 10:59 am

    Thanks for this post, Martin. I didn’t know this extension existed and will most certainly give it a try. In principle, this is a good and even necessary initiative.

    At least in Europe, and to some extent in the US as well, many university research projects can exist thanks to public funding in the form of government subsidies, grants etc.It is basically wrong – in fact, unethical – to hide the results of such publicly-funded projects from the same public behind a paywall. Even more so, if this barred public includes independent researchers who just happen to not belong to one of the institutions with paywall access.

    Most of these research publication paywalls exist not to prevent premature leaking of results, which by itself might in some situations be a legitimate reason. These paywalls serve primarily to satisfy the greed of a few prominent science publishers who (aided by monopolies and tactics like peer pressure) hijack research publications that, having been publicly funded, ought to be freely published from day one.

    Any initiative that can help to break these immoral and even harmful research publication paywalls, deserves a warm applause.

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