How to get title and pdf (and perhaps other metadata like author) from DOI I have a bunch of DOIs, now I would like to fetch the corresponding PDF and the title and authors, creation/publish date, keywords, abstract if possible, etc. I understand that many articles are behind a paywall so don't expect to get the PDFs for those. But I would still like to get the other metadata for those articles, even though they are behind the paywall (since I imagine that info is public).

To summarize, looking for some/all of these properties in preferably JSON or XML form (except the PDF, in PDF form, if freely available):


title
authors
journal
publicationDate
keywords
abstract/description


I tried looking here at the DOI API but it only seems to provide this:

{
  "responseCode": 1,
  "handle": "10.1000/1",
  "values": [
    {
      "index": 100,
      "type": "HS_ADMIN",
      "data": {
        "format": "admin",
        "value": {
          "handle": "0.NA/10.1000",
          "index": 200,
          "permissions": "011111111111"
        }
      },
      "ttl": 86400,
      "timestamp": "2000-04-13T15:08:57Z"
    },
    {
      "index": 1,
      "type": "URL",
      "data": { "format": "string", "value": "http://www.doi.org/index.html" },
      "ttl": 86400,
      "timestamp": "2004-09-10T19:49:59Z"
    }
  ]
}


I saw CORE, which might have the metadata, but it isn't public domain / free / open source for commercial use, which I would like. Also checked at the Elsevier APIs (Mendeley and Scopus), but they are not free for commercial use either.
the Crossref REST API is public and doesn't have a license - all our metadata are available for reuse without restriction. That's because we believe that metadata are facts and facts cannot be owned or licensed. (The license CC 4 refers only to the documentation on how to use the API :-))

We have 105 million DOIs about 25% of those have full-text links that go to HTML or PDFs. I'm not sure of the exact queries you'll need but if you end up using it and need help you can open tickets there on GitHub.