Accessing research papers: open access tools and shadow libraries
by Danny Willems
Academic knowledge is locked behind paywalls. Publishers charge $30-50 per article, and institutional subscriptions cost universities millions per year. Meanwhile, researchers receive no royalties from these sales, and publicly funded research remains inaccessible to the public that funded it.
This page lists tools and resources to access research papers, organized from fully legal open access platforms to shadow libraries.
Open access platforms and tools
OpenAlex
OpenAlex is a fully open catalog of the global research system, named after the ancient Library of Alexandria. Built by the nonprofit OurResearch, it launched in January 2022 as a successor to the discontinued Microsoft Academic Graph. OpenAlex indexes over 250 million scholarly works, including articles, datasets, books, and dissertations. The entire dataset is available under the CC0 license via a web GUI, REST API, and full data dump.
Unpaywall
Unpaywall is a free, open-source browser extension for Chrome and Firefox, also made by OurResearch. When you view a paywalled journal article, Unpaywall checks its database of over 49 million legal, open-access articles. If an open version exists, a green tab appears on the page. Click the tab and read for free, legally. The source code is available on GitHub.
arXiv
arXiv is the original preprint server, founded in 1991 by Paul Ginsparg at Los Alamos National Laboratory (now hosted by Cornell University). It hosts over 2.4 million preprints in physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering, and economics. Papers are freely accessible without any paywall.
PubMed Central
PubMed Central (PMC) is a free full-text archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health. It provides free access to over 10 million articles. The NIH public access policy mandates that research funded by NIH be deposited in PMC within 12 months of publication.
CORE
CORE is the world’s largest collection of open-access research papers, aggregating over 250 million articles from more than 30,000 sources worldwide. It harvests content from institutional and subject repositories, and open access journals.
Semantic Scholar
Semantic Scholar is an AI-powered academic search engine developed by the Allen Institute for AI. It indexes over 200 million papers across all fields of science and uses machine learning to surface relevant results, extract key figures and tables, and provide citation context.
DOAJ (Directory of Open Access Journals)
DOAJ indexes over 20,000 peer-reviewed open-access journals that meet strict quality criteria. It serves as a whitelist for legitimate open-access publishing.
bioRxiv and medRxiv
bioRxiv (biology) and medRxiv (medicine) are preprint servers operated by Cold Spring Harbor Laboratory. They host manuscripts before formal peer review.
SSRN
SSRN (Social Science Research Network) hosts preprints in social sciences, humanities, and law. Now owned by Elsevier, but still provides free access to most papers.
Internet Archive
Internet Archive and its Open Library project provide access to millions of books through controlled digital lending. The Wayback Machine can also surface older versions of papers that were once freely available.
Google Scholar
Google Scholar indexes approximately 400 million academic documents. While it doesn’t host papers directly, it links to free versions when available, including preprints and author-hosted copies.
BASE (Bielefeld Academic Search Engine)
BASE is operated by Bielefeld University Library in Germany. It provides access to over 400 million documents from more than 11,000 content providers, with a strong focus on open-access resources.
Open Access Button
Open Access Button is a browser extension and web tool that searches for free, legal copies of research papers. If no free copy exists, it can automatically send an access request to the author.
Shadow libraries
Shadow libraries are collections of copyrighted content made available without permission from copyright holders. They exist because the current academic publishing model charges for access to publicly funded research while paying nothing to the researchers who produce it. For a broader context, see the Wikipedia article on shadow libraries.
Sci-Hub
Sci-Hub was created in 2011 by Alexandra Elbakyan, a Kazakhstani graduate student who could not afford access to papers she needed for her research. It provides free access to over 85 million research papers by bypassing publisher paywalls. Sci-Hub is the most widely used shadow library for academic papers, and has been the subject of multiple lawsuits from publishers like Elsevier and Springer Nature. Domain names change frequently due to legal action.
Library Genesis (LibGen)
Library Genesis is one of the oldest and largest shadow libraries, hosting over 2.4 million non-fiction books, 80 million scientific articles, 2.2 million fiction books, and hundreds of thousands of comics and magazine issues. It started in the early 2000s from Russian scientific and academic communities. Like Sci-Hub, its domain changes frequently.
Z-Library
Z-Library began as a mirror of Library Genesis but has since expanded to include works not available on LibGen. It was one of the largest online libraries before law enforcement operations in 2022 seized its domains and led to the arrest of two alleged operators. It has since relaunched using alternative access methods.
Anna’s Archive
Anna’s Archive is an open-source search engine and metasearch for shadow libraries. It was launched in 2022 by the pseudonymous “Anna” shortly after the Z-Library seizure. It aggregates records from Library Genesis, Sci-Hub, Z-Library, and other sources into a single searchable interface. Previously known as Pirate Library Mirror (PLIMI). See also the Wikipedia article.
Memory of the World
Memory of the World is a network of interconnected shadow libraries, each maintained locally and independently. It focuses on critical theory, philosophy, and humanities texts, operating as a decentralized collective.
The Anarchist Library
The Anarchist Library is an open archive focused on anarchism and related topics. It hosts texts in multiple languages and formats.
UbuWeb
UbuWeb is an online archive of avant-garde art, founded by conceptual artist Kenneth Goldsmith. It hosts a vast collection of sound, film, video, and text works that are difficult or impossible to find elsewhere.
AAAAARG
AAAAARG (Artists, Architects, and Activists Reading Group) was an online text repository created by artist Sean Dockray in 2005. It focused on critical theory, art, and architecture texts. As of 2025, it is offline.
Monoskop
Monoskop is a wiki for collaborative studies of the arts, media, and humanities. It hosts a significant collection of texts, books, and resources related to media art, digital culture, and critical theory.
Other strategies
Emailing the author
Researchers receive no money from publisher paywalls. Most will happily send you a PDF of their paper if you email them directly. Look for the corresponding author’s email address in the abstract or on their institutional page.
Your local library
Public and university libraries often provide free access to academic databases like JSTOR, Web of Science, and Scopus. Some libraries offer remote access through digital borrowing programs. Many countries have national licensing agreements that provide broader access.
Interlibrary loan (ILL)
If your library does not have access to a specific paper, you can request it through interlibrary loan. This is a free service offered by most academic and public libraries.
ResearchGate and Academia.edu
Researchers often upload copies of their own papers to ResearchGate and Academia.edu. These self-archived copies are typically legal under the “green open access” provisions of most publisher agreements.
Social media
Posting the DOI or title of a paper on Twitter/X with the hashtag #ICanHazPDF
is a long-standing tradition in the academic community. Someone with
institutional access will often send you the paper.