Unpaywall

Open access papers, free research papers and paper links

Find free-to-read scholarly papers and their legal copies.

Get free version

Get free version

Find a legal free copy of a paper by title or DOI, with its best available link and other copies. If no free copy is indexed, copy links are null.

Your information

Paper

Paper title or DOI, for example The Moral Machine experiment or 10.1038/s41586-018-0637-6.

More options

AuthorOptional

Optional author name to distinguish papers with similar titles, for example Edmond Awad.

1 credit per completed run

The same inputs also work from your code or an AI assistant. See For developers.

Example results

Initial sequencing and analysis of the human genome

yesOpen free paper

Journal: Nature
Year: 2,001
Repository: Springer Science and Business Media LLC
Version: published
Licence: Public domain
DOI: 10.1038/35057062

Open paper record

Other free copies

University of Michigan
Open copy record

About the Unpaywall tool

Unpaywall finds a legal free copy of a paper using its title or DOI, with an optional author name to distinguish similar titles.

Get free version returns the best available link and other copies; if no free copy is indexed, copy links are null.

Built from unpaywall.org and crossref.org. Last checked Sep 29, 2026.

Actions

Get free version

1 credit

Find a legal free copy of a paper by title or DOI, with its best available link and other copies. If no free copy is indexed, copy links are null.

Uses Unpaywall and crossref.org.

What you provide

Field	Type	Required	Description
Paper`paper`	Text	Required	Paper title or DOI, for example The Moral Machine experiment or 10.1038/s41586-018-0637-6.Example: 10.1038/35057062
Author`author`	Text	Optional	Optional author name to distinguish papers with similar titles, for example Edmond Awad.Example: Edmond Awad

What you get

Field	Type	Description
DOI`doi`	Text	Example: 10.1038/35057062
Host`host`	Text	Example: Springer Science and Business Media LLC
Year`year`	Number	Example: 2001
Title`title`	Text	Example: Initial sequencing and analysis of the human genome
Journal`journal`	Text	Example: Nature
Licence`licence`	Text	Example: Public domain
Version`version`	Text	Example: Published
Free to Read`free_to_read`	Text	Example: Yes
Landing Page`landing_page`	Text	Example: https://doi.org/10.1038/35057062
Best Free Link`best_free_link`	Text	Example: https://www.nature.com/articles/35057062.pdf
Other Free Copies`other_free_copies`	List
Host`other_free_copies[].host`	Text	Example: University of Michigan
Link`other_free_copies[].link`	Text	Example: https://hdl.handle.net/2027.42/62798
Landing Page`other_free_copies[].landing_page`	Text	Example: https://hdl.handle.net/2027.42/62798

Example result

For Paper: 10.1038/35057062

JSON

{
  "doi": "10.1038/35057062",
  "host": "Springer Science and Business Media LLC",
  "year": 2001,
  "title": "Initial sequencing and analysis of the human genome",
  "journal": "Nature",
  "licence": "Public domain",
  "version": "published",
  "free_to_read": "yes",
  "landing_page": "https://doi.org/10.1038/35057062",
  "best_free_link": "https://www.nature.com/articles/35057062.pdf",
  "other_free_copies": [
    {
      "host": "University of Michigan",
      "link": "https://hdl.handle.net/2027.42/62798",
      "landing_page": "https://hdl.handle.net/2027.42/62798"
    }
  ]
}

For developers

Call it from your code with one request. Change the values in input to run it on new data. To get an API key, open Developers at the bottom of Studio, turn on Developer mode and go to API keys.

cURL

curl 'https://api.fous.com/v1/query' \
  --fail-with-body --silent --show-error --max-time 180 \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H 'Content-Type: application/json' \
  --data-raw '{
  "api": "@unpaywall",
  "visibility": "public",
  "operation": "get_free_version",
  "version": 1,
  "input": {
    "paper": "10.1038/35057062"
  },
  "response": {
    "format": "json"
  }
}'

What you can do with it

Find free versions of papers by title or DOI
Distinguish papers with similar titles using an author name
Compare available copies by host and landing page
Check a paper’s journal, year, licence, and version

Questions about Unpaywall

Can I run it with my own inputs?

Yes. Change the inputs in Studio and press Run, or send new inputs from your code, or ask a connected AI assistant.

Can I call this Unpaywall tool as an API?

Yes. Send a POST request to /v1/query with your Fous API key and the inputs, and get JSON back.

How much does it cost?

Each completed run costs 1 credit. Failed runs without a completed receipt are free; completed work can remain charged if delivery is interrupted. With pay as you go, a credit costs 1¢. Monthly plans cost less per credit.

Do I need a Unpaywall account?

No. You only need a Fous account.

How current is the data?

Fous gets the data from unpaywall.org when you run it. Some results are reused for up to 24 hours, and results that use your account or key are never reused. It was last verified on Sep 29, 2026.