What is Unpaywall API?

Unpaywall API is a Web service provided by OurResearch that allows you access its open database of 33,044,881 free research papers.

Technical information on Unpaywall API:

URL: https://api.unpaywall.org/v2/{doi}?email={email}
URL: https://api.unpaywall.org/v2/search?query={keywords}&email={email}[&page=n]
  doi: DOI string
  email: your email address 
  keywords: Keywords to search 
  n: index of the result page to return  
Response format: JSON 

Here is an example on how to use Unpaywall API:

fyicenter$ curl 'https://api.unpaywall.org/v2/10.1038/d41586-018-05968-3?email=bob@abc.com'

{
    "best_oa_location": {
        "endpoint_id": null,
        "evidence": "open (via page says license)",
        "host_type": "publisher",
        "is_best": true,
        "license": "cc-by",
        "oa_date": "2018-08-01",
        "pmh_id": null,
        "repository_institution": null,
        "updated": "2021-10-07T08:11:52.739361",
        "url": "https://doi.org/10.1038/d41586-018-05968-3",
        "url_for_landing_page": "https://doi.org/10.1038/d41586-018-05968-3",
        "url_for_pdf": null,
        "version": "publishedVersion"
    },
    "data_standard": 2,
    "doi": "10.1038/d41586-018-05968-3",
    "doi_url": "https://doi.org/10.1038/d41586-018-05968-3",
    "first_oa_location": {
        "endpoint_id": null,
        "evidence": "open (via page says license)",
        "host_type": "publisher",
        "is_best": true,
        "license": "cc-by",
        "oa_date": "2018-08-01",
        "pmh_id": null,
        "repository_institution": null,
        "updated": "2021-10-07T08:11:52.739361",
        "url": "https://doi.org/10.1038/d41586-018-05968-3",
        "url_for_landing_page": "https://doi.org/10.1038/d41586-018-05968-3",
        "url_for_pdf": null,
        "version": "publishedVersion"
    },
    "genre": "journal-article",
    "has_repository_copy": false,
    "is_oa": true,
    "is_paratext": false,
    "journal_is_in_doaj": false,
    "journal_is_oa": false,
    "journal_issn_l": "0028-0836",
    "journal_issns": "0028-0836,1476-4687",
    "journal_name": "Nature",
    "oa_locations": [
        {
            "endpoint_id": null,
            "evidence": "open (via page says license)",
            "host_type": "publisher",
            "is_best": true,
            "license": "cc-by",
            "oa_date": "2018-08-01",
            "pmh_id": null,
            "repository_institution": null,
            "updated": "2021-10-07T08:11:52.739361",
            "url": "https://doi.org/10.1038/d41586-018-05968-3",
            "url_for_landing_page": "https://doi.org/10.1038/d41586-018-05968-3",
            "url_for_pdf": null,
            "version": "publishedVersion"
        }
    ],
    "oa_locations_embargoed": [],
    "oa_status": "hybrid",
    "published_date": "2018-08-01",
    "publisher": "Springer Science and Business Media LLC",
    "title": "How Unpaywall is transforming open science",
    "updated": "2021-10-07T08:12:56.330663",
    "year": 2018,
    "z_authors": [
        {
            "family": "Else",
            "given": "Holly",
            "sequence": "first"
        }
    ]
}

You can follow the "url_for_landing_page" from the output to read the paper.

⇒ oadoi.org - Open Access DOI Database

⇐ Unpaywall Browser Plugin to Access Papers

⇑ Other DOI Tools and Resources

⇑⇑ DOI - Frequently Asked Questions