omnischolar/crossref

Crossref for omnisense/omnischolar: the reference metadata of any work with a Crossref DOI - title, authors and their ORCIDs, journal or book, volume, pages, publisher, ISBNs, licence, the citation count Crossref knows - the works an ORCID was deposited with, the works of a name, and a bibliographic search. The source calls Crossref's REST API, without a key:

The base address is CrossrefSource::BASE_URI (https://api.crossref.org/). There is no sandbox.

Installation

composer require omnischolar/crossref

Requires PHP 8.2, omnisense/omnischolar (1.x) and symfony/http-client (6.4, 7 or 8). In a Symfony application with OmnischolarBundle, the factory is registered as soon as the package is installed.

Credentials

None. A mailto puts the calls in Crossref's "polite" pool (three calls a second, as Crossref's documentation said in 2026); without it, the public pool.

Options

Capabilities

capabilities(): works, work, search, citations, abstracts.

Behaviour

Lists. from → filter=from-pub-date:<year>, to → until-pub-date:<year>-12-31, types → type: with Crossref's types for each kind (journal-article; book, monograph, edited-book, reference-book, proceedings; book-chapter, book-section, book-part, reference-entry; proceedings-article; posted-content; dissertation; report, report-component, standard; dataset; peer-review; other, component); domains is refused; openAccess is not read. sort: newest → published desc, oldest → published asc, cited → is-referenced-by-count desc, relevance → score desc. rows = limit 1 to 1000; the cursor is an offset (Crossref's cursors cannot sort by date), and paging stops at 10 000 (MAX_OFFSET). Lists ask only the fields the models read (select); work() reads the whole record.

Works by name. Crossref's author query is fuzzy: its answers come by relevance and are kept only when one of their authors has the family name asked and the same first given name - or its initial, when the work gives initials only (K. Nakatani, not Kenji Nakatani). Page::$total is then null.

A work. Title and subtitle; type from Crossref's (posted-content is a preprint unless its subtype says otherwise); authors and editors with given and family names, ORCID and affiliations; year and date from issued (else published); venue from the container title (a journal, a book for a chapter, a conference for a proceedings article, a book series for a book, a repository for a preprint; its ISSNs, publisher and abbreviation) or the event's name; publisher, volume, issue, pages, edition; abstract (JATS tags stripped); language; the publisher's landing page as url; licence; citation count (is-referenced-by-count); subjects as keywords; identifiers: the DOI and every ISBN (print and electronic). No open-access status, no PDF.

Example

<?php

require __DIR__.'/vendor/autoload.php';

use Omnischolar\Crossref\CrossrefSourceFactory;
use Symfony\Component\HttpClient\HttpClient;

$crossref = (new CrossrefSourceFactory(HttpClient::create()))->create(['mailto' => getenv('OMNISCHOLAR_MAILTO') ?: null]);

$w = $crossref->work('10.1039/D4SC04973J');
echo $w->title, "\n", $w->venue?->name, ' ', $w->volume, '(', $w->issue, ') ', $w->pages, '; ', $w->publisher, '; cited ', $w->citations, '; ', $w->license, "\n";
foreach ($w->authors as $a) {
    echo '  ', $a->sortName(), ' ', $a->orcid() ?? '', "\n";
}

Acid-sensitive photoswitches: towards catalytic on-demand release of stored light energy
Chemical Science 15(39) 16034-16039; Royal Society of Chemistry (RSC); cited 8; http://creativecommons.org/licenses/by/3.0/
  Chocron, Léa 
  Baggi, Nicolò 0000-0003-4743-5151
  Ribeiro, Enrique 0000-0001-5795-7418
  Goetz, Vincent 0000-0001-5700-6487
  Yu, Pei 0000-0003-1801-1579
  Nakatani, Keitaro 0009-0005-1387-7295
  Métivier, Rémi 0000-0001-5612-8327

(called live on 2026-10-26 at 14:18 UTC, from the core's harness image, without a mailto)

In Symfony:

omnischolar:
    sources:
        crossref: { factory: crossref, options: { mailto: '%env(OMNISCHOLAR_MAILTO)%' } }

Errors

Verified, and not

Tested offline: Tests/CrossrefSourceTest.php (6 tests), on MockHttpClient with answers recorded on 2026-10-04 - a work by DOI (10.1039/d4sc04973j), the eight works deposited with Juan Maldacena's ORCID, the answer to query.author=Monica Neagoy (four of hers among others). Called live on 2026-10-04 and on 2026-10-26 (the example above).

Limits of the service: works by name rest on a fuzzy query - a name shared with other people of the same family name and first name cannot be told apart; works by ORCID are those whose publisher deposited the ORCID (some placeholder ORCIDs are used by thousands of unrelated works); offsets stop at 10 000.

Responsibility

An independent, unofficial client, not affiliated with Crossref. Whoever runs it complies with Crossref's terms (REST API documentation): see the README's Responsibility section.