How to Download a Research Paper by DOI (Free and Legal, 2026)

Paste a DOI, get the paper: how to download research papers for free using a DOI, legally. Where to find the DOI, 8 legal options, an author email template and bulk DOIs.

Quick answer

To download a paper by DOI, paste the DOI (for example 10.1038/nature14539) into the Ocean of Papers search box. It finds the exact paper and shows a PDF button if a free, legal open-access copy exists. If there is no button, try the Unpaywall extension, PubMed Central, a preprint server, the author or your library.

Paste a DOI

Doi to PDF in 30 Seconds

If you already have a DOI, you do not need to search by title or guess keywords. A DOI points to exactly one paper, so the fastest route from DOI to PDF is:

Copy the DOI, for example 10.1038/nature14539.
Paste it into the search box on Ocean of Papers.
Click the PDF button on the result. It appears only when a free, legal open-access copy exists (from Unpaywall, PubMed Central, arXiv, bioRxiv or medRxiv).

No account is needed to search or open PDFs. If there is no PDF button, the paper is probably paywalled and has no known free copy yet. The rest of this guide covers what to do then.

This page is only about downloading by DOI. For a broader guide to free paper downloads (searching by topic, filters, phones), see how to download research papers for free, and for a list of sites, see websites to download research papers free.

Updated October 2026.

What Is a DOI (and Where to Find It)?

A DOI (Digital Object Identifier) is a permanent ID given to a published paper, book chapter, dataset or preprint. Even if the publisher changes its website, the DOI keeps pointing to the right place.

Annotated example

10.1038/nature14539

10. → every DOI starts with "10."
1038 → the registrant code (here, the publisher Nature Portfolio)
/ → separates the prefix from the suffix
nature14539 → the suffix the publisher chose for this one paper

This DOI belongs to LeCun, Bengio and Hinton, "Deep learning", Nature 521, 436–444 (2015). Put https://doi.org/ in front and you get a link that always resolves to the paper's official page: https://doi.org/10.1038/nature14539.

Where to find a DOI

On the paper's first page, usually in the header or footer, often written as "doi:10.xxxx/…" or "https://doi.org/10.xxxx/…"
On the journal web page, near the title or under "Cite this article"
In a reference list, at the end of most APA, Vancouver and Harvard references
In a reference manager (Zotero, Mendeley, EndNote) in the DOI field
In search results: Ocean of Papers shows the DOI on each paper's details

Tips: copy the DOI without spaces or a trailing full stop. Ocean of Papers accepts a bare DOI, "doi:10.…" or a full https://doi.org/ link. arXiv papers also have DOIs that start with 10.48550/arXiv.

How to Download a Paper Using a DOI (Step by Step)

Copy the DOI from the reference, citation or journal page.

Paste it into Ocean of Papers. The search matches the exact paper. It searches OpenAlex, PubMed, arXiv, bioRxiv, medRxiv and Europe PMC, which together cover 250M+ papers.

Check the result. Make sure the title, authors and year match what you expected. If the DOI was copied wrongly you may get no result or a different paper.

Click PDF. If a legal open-access copy exists, the PDF button opens it. The copy may be the publisher version, an accepted manuscript in a repository, or a preprint. Check which version you have before quoting page numbers.

Save the citation too. From the same result you can copy the citation in APA, MLA, Chicago, Harvard, Vancouver or BibTeX, or export it as RIS or BibTeX for your reference manager.

No PDF button? Go to the legal options table below and the what to do when there is no free copy section.

While you are on the result, you can also click Build map to see papers connected to it (references, citing papers and similar work). That is useful when one paper is the start of a bigger reading list; see how to find papers that cite a paper.

Copy the DOI — e.g. 10.1038/nature14539
Paste into Ocean of Papers — Finds the exact paper across 6 sources
Check the match — Title, authors and year
Click PDF — Shown only when a legal free copy exists
Copy or export the citation — APA, MLA, BibTeX, RIS…

Legal Ways to Download Articles for Free with a DOI

These are the legal routes, in the order we suggest trying them. None of them can unlock a paper that has no free version anywhere, but together they find most of the free copies that exist.

Ocean of Papers: paste the DOI into search. Shows a PDF button from Unpaywall, PubMed Central, arXiv, bioRxiv or medRxiv when one exists. Also gives citations and a citation map.
Unpaywall browser extension: install it from unpaywall.org (Chrome and Firefox). When you open a paper's publisher page, a green tab means a free legal copy was found; click it to open.
doi.org resolver: type https://doi.org/ followed by the DOI. It takes you to the official page. If the article is open access, the PDF is there.
PubMed Central (PMC): free full text for many biomedical and life-science papers, including many funded by the US NIH. Search the title or DOI at pmc.ncbi.nlm.nih.gov.
Preprint servers: many papers have an earlier version on arXiv (physics, maths, CS, economics) or bioRxiv (biology). Search by title, since the preprint has its own DOI.
CORE: core.ac.uk collects open-access papers from university and subject repositories worldwide, where authors often deposit accepted manuscripts.
Ask the author: email the corresponding author for a copy (template below). The Open Access Button used to automate this, but its service was shut down in 2025, so write to the author yourself.
Your library and interlibrary loan: if your university or college subscribes, log in through the library to get the publisher PDF. If not, ask the library for an interlibrary loan or document delivery request.

Legal DOI-to-PDF options compared
Feature	What it does	Accepts a DOI?	Limits	Cost
Ocean of Papers	Finds the exact paper; PDF button when a legal free copy exists; citations and maps	Yes	No PDF if no open copy exists anywhere	Free (maps: 5 new/month on free plan)
Unpaywall extension	Shows a green tab on publisher pages when a free legal copy exists	Works on the article page	Chrome and Firefox only; one paper at a time	Free
doi.org resolver	Sends you to the official publisher page	Yes	Only gives a PDF if the publisher version is open	Free
PubMed Central	Free full text archive for biomedical and life sciences	Search by title or DOI	Mostly health and life sciences	Free
arXiv / bioRxiv	Preprints, often close to the final version	Search by title	Not peer-reviewed in that version; field-specific	Free
CORE	Aggregates repository copies (accepted manuscripts)	Search by title or DOI	Coverage varies; version may differ from published	Free
Author request	The author sends you a copy	You give the DOI in your email	Can take days; no reply sometimes	Free
Library / interlibrary loan	Publisher PDF through subscription or document delivery	Give the DOI on the request form	Needs library membership; ILL can take days	Usually free for students

What to Do When There Is No Free Copy

Many recent papers have a free version somewhere; older papers less often. If you have tried the options above and still have no PDF, work through this list.

1. Look for another version of the same work. Search the paper's title (not the DOI) on Ocean of Papers. A preprint or accepted manuscript often has a different DOI or none at all, so a title search can find it when a DOI search does not. Also check the authors' university pages and profiles.

2. Read the abstract and decide if you need the full text. For background citations the abstract plus a review that discusses the paper may be enough. For anything you analyse or quote, you need the full text.

3. Email the author. Researchers are usually happy to share their work, and many publishers allow authors to send a copy for personal research use. Use the corresponding author's email from the article page. Keep it short:

Subject: Request for a copy of your paper (DOI: 10.xxxx/xxxxx)

Dear Dr [Surname],

I am a [master's student / PhD student / researcher] at [university] working on [one-line topic]. I would like to read your paper "[Title]" ([Journal], [Year]), DOI: [10.xxxx/xxxxx], but I do not have access to it through my institution.

Would you be able to send me a copy for my personal research use? I would be very grateful.

Thank you for your time.

Kind regards, [Your name] [Course or position, university]

4. Ask your library. Even if your library does not subscribe to the journal, it can often get a copy through interlibrary loan or document delivery. Give them the full reference and the DOI.

5. Find an alternative source. If none of this works in time, look for other papers that make the same point. Build a citation map from the paper's DOI and check Similar or Derivative works; newer open-access papers often summarise the same findings.

Many DOIs at Once: Paste a List into Your Library

If you have a reference list with dozens of DOIs (for a literature review, a reading list or a supervisor's suggestions), you do not need to paste them one by one.

Sign in with a free account and open your library.
Click Import, then choose the Paste DOIs tab.
Paste your list. It can be bare DOIs, https://doi.org/ links, or a whole reference list copied from a paper; the tool picks out the DOIs. It shows how many it found.
Click Next. Each DOI is matched to the paper in OpenAlex. You can match up to 300 references in one import.
Review the matches, choose a project and add them.

Every matched paper is saved with its details, and papers with a legal open-access copy show a PDF link in the project. You can then export the whole project as BibTeX, RIS, CSV or text, or open Discover to see papers your project is missing (for example, papers cited by many of your imported ones).

The same Import button also accepts a BibTeX or RIS file and a one-time import from Zotero. Writing a review from these papers? See how to write a literature review.

Note: this matches papers and gives you legal PDF links; it does not mass-download files from publishers.

Why We Do Not Recommend Sci-Hub or Similar Sites

When you search for "free paper download" or "DOI to PDF", you will see sites that offer any paper by DOI. Some of them work by copying paywalled papers without the publisher's permission. We do not link to them, for a few reasons:

Copyright. Downloading pirated copies breaks copyright law in many countries, and some universities treat it as a breach of their IT rules.
Security. Unofficial mirrors and copycat sites can carry malware, pop-ups and phishing pages.
Reliability. Mirrors appear and disappear, and you cannot always tell if a file is the final version.
You often do not need them. For a large share of papers, a legal free copy already exists. The routes above find it, and authors and libraries can usually help with the rest.

Legal open access is growing every year, as funders require free access and more authors post preprints and accepted manuscripts.

FAQ

How do I download research papers for free using a DOI?

Paste the DOI into Ocean of Papers. If a free, legal copy of the paper exists (on PubMed Central, arXiv, bioRxiv, medRxiv or another open-access source found through Unpaywall), a PDF button appears on the result. Click it to open and save the paper.

Can I download articles for free with a DOI if they are paywalled?

Only if a legal free version exists, such as a preprint or an accepted manuscript in a repository. If not, ask the author for a copy, or use your library or interlibrary loan. A DOI alone does not unlock a paywall.

What is the fastest DOI to PDF method?

Paste the DOI into Ocean of Papers and click the PDF button. If you are already on a publisher's page, the Unpaywall browser extension shows a green tab when a free copy exists.

How do I download a paper using a DOI on my phone?

Open Ocean of Papers in your phone browser, paste the DOI into the search box, and tap PDF. The file opens in your browser, where you can save or share it.

Why does a DOI search show the paper but no PDF button?

The PDF button only appears when a legal open-access copy is known. No button means the paper is probably paywalled with no free version indexed yet. Try a title search for a preprint, email the author, or ask your library.

Is free paper download by DOI legal?

Yes, when the copy comes from a legal source: open-access journals, PubMed Central, preprint servers, university repositories, the author or your library. Downloading pirated copies from shadow libraries is not legal in many countries.

Can I download many papers at once from a list of DOIs?

You can match many DOIs at once: open your library, click Import, choose Paste DOIs and paste the list (up to 300 per import). The papers are saved to a project with PDF links where legal free copies exist, and you can export the list as BibTeX, RIS or CSV.

Where do I find the DOI of a paper?

Look on the first page of the PDF, under the title on the journal website, at the end of a reference in APA or Vancouver style, or in your reference manager. It always starts with "10." followed by a slash and a suffix.