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CrossRef REST API

Version History

  • V1: 2013-09-08, first draft.
  • V2: 2013-09-24, reference platform deployed
  • v3: 2013-09-25, reworked filters. Added API versioning doc
  • v4: 2013-09-25, more filter changes.
  • v5: 2013-09-27, doc mime-type and message-type relationship
  • v6: 2013-10-01, updated sample & added examples with filters
  • v6: 2013-10-01, corrected warning date
  • v7: 2013-10-02, fixed typos
  • v8: 2013-10-17, updated warning. Added email address
  • v9: 2013-12-13, update example urls
  • v10: 2013-12-13, /types routes, type filter, issn filter
  • v11: 2013-12-14, indexed timestamps, has-archive and archive implemented
  • v12: 2014-01-06, directory filter
  • v13: 2014-02-10, new /members, /publishers becomes /prefixes, new member filter, publisher filter becomes prefix
  • v14: 2014-02-14, new has-funder filter.
  • v15: 2014-02-27, new /licenses route
  • v16: 2014-05-19, new /journals route, new CrossMark (updates and update policy) filters, new sort and order parameters
  • v17: 2014-05-19, new facet query parameter
  • v18: 2014-05-29, new /works/{doi}/agency route
  • v19: 2014-06-23, new textual filters - container-title, publisher-name, category-name.
  • v20: 2014-06-24, OR filter queries, type-name filter.
  • v21: 2014-07-01, new award.number and award.funder relational filters.
  • v22: 2014-07-16, changed title to more accurately reflect scope of API.
  • v23, 2014-09-01, semantics of mutliple filters, dot filters
  • v24, 2014-10-15, Added info on license of CrossRef metadata itself. Doh.
  • v25, 2015-05-06, Added link to issue tracker. Removed Warning section.
  • v26, 2015-10-20, Added new filters - from-created-date, until-created-date, affiliation, has-affiliation, assertion-group, assertion, article-number, alternative-id
  • v27, 2015-10-30, Added cursor parameter to /works resources
  • v28, 2016-05-09, Added link to source of category lables
  • v29, 2016-05-24, Added field queries

Background

See the document, CrossRef metadata best practice to support key performance indicators (KPIs) for funding agencies, for background.

Reporting issues

If you have suggestions or encounter problems with the API or the documentation, please report them on our issue tracker.

If you have other queries, please contact us at:

License

CrossRef asserts no claims of ownership to individual items of bibliographic metadata and associated Digital Object Identifiers (DOIs) acquired through the use of the CrossRef Free Services. Individual items of bibliographic metadata and associated DOIs may be cached and incorporated into the user's content and systems. More information can be found on our web site.

Overview

The API is generally RESTFUL and returns results in JSON. JSON formats returned by the API are documented here.

The API will only work for CrossRef DOIs. You can test the registration agency for a DOI using the following route:

http://api.crossref.org/works/{doi}/agency

Testing the following CrossRef DOI:

10.1037/0003-066X.59.1.29

Using the URL:

http://api.crossref.org/works/10.1037/0003-066X.59.1.29/agency

Will return the following result:

{
  status: "ok",
  message-type: "work-agency",
  message-version: "1.0.0",
  message: {
    DOI: "10.1037/0003-066x.59.1.29",
    agency: {
      id: "crossref",
      label: "CrossRef"
    }
  }
}

If you use any of the API calls listed below with a non-CrossRef DOI, you will get a 404 HTTP status response. Typical agency IDs include crossref, datacite, medra and also public for test DOIs.

Results Overview

All results are returned in JSON. There are two general types of results:

  • Singletons
  • Lists

The mime-type for API results is application/vnd.crossref-api-message+json

Singletons

Singletons are single results. Retrieving metadata for a specific identifier (e.g. DOI, ISSN, funder_identifier) typically returns in a singleton result.

Lists

Lists results can contain multiple entries. Searching or filtering typically returns a list result. A list has two parts:

  • Summary, which include the following information:
    • status (e.g. "ok", error)
    • message-type (e.g. "work-list" )
    • message-version (e.g. 1.0.0 )
  • Items, which will will contain the items matching the query or filter.

Note that the "message-type" returned will differ from the mime-type:

  • funder (singleton)
  • prefix (singleton)
  • member (singleton)
  • work (singleton)
  • work-list (list)
  • funder-list (list)
  • prefix-list (list)
  • member-list (list)

Normally, an API list result will return both the summary and the items. If you want to just retrieve the summary, you can do so by specifying that the number of rows returned should be zero.

Sort order

If the API call includes a query, then the sort order will be by the relevance score. If no query is included, then the sort order will be by DOI update date.

Resource Components

Major resource components supported by the CrossRef API are:

  • works
  • funders
  • members
  • prefixes
  • types
  • journals

These can be used alone like this

resource description
/works returns a list of all works (journal articles, conference proceedings, books, components, etc), 20 per page
/funders returns a list of all funders in the FundRef Registry
/members returns a list of all CrossRef members (mostly publishers)
/types returns a list of valid work types
/licenses return a list of licenses applied to works in CrossRef metadata
/journals return a list of journals in the CrossRef database

Resource components and identifiers

Resource components can be used in conjunction with identifiers to retrieve the metadata for that identifier.

resource description
/works/{doi} returns metadata for the specified CrossRef DOI.
/funders/{funder_id} returns metadata for specified funder and its suborganizations
/prefixes/{owner_prefix} returns metadata for the DOI owner prefix
/members/{member_id} returns metadata for a CrossRef member
/types/{type_id} returns information about a metadata work type
/journals/{issn} returns information about a journal with the given ISSN

Combining resource components

The works component can be appended to other resources.

resource description
/works/{doi} returns information about the specified CrossRef DOI
/funders/{funder_id}/works returns list of works associated with the specified funder_id
/types/{type_id}/works returns list of works of type type
/prefixes/{owner_prefix}/works returns list of works associated with specified owner_prefix
/members/{member_id}/works returns list of works associated with a CrossRef member (deposited by a CrossRef member)
/journals/{issn}/works returns a list of works in the given journal

Parameters

Parameters can be used to query, filter and control the results returned by the CrossRef API. They can be passed as normal URI parameters or as JSON in the body of the request.

parameter description
query limited DisMax query terms
filter={filter_name}:{value} filter results by specific fields
rows={#} results per per page
offset={#} result offset
sample={#} return random N results
sort={#} sort results by a certain field
order={#} set the sort order to asc or desc
facet=t enable facet information in responses

Multiple filters can be specified by separating name:value pairs with a comma:

http://api.crossref.org/works?filter=has-orcid:true,from-pub-date:2004-04-04

Example query using URI parameters

http://api.crossref.org/funders/100000015/works?query=global+state&filter=has-orcid:true&rows=1

Queries

Queries support a subset of DisMax, so, for example you can refine queries as follows.

Works that include "renear" but not "ontologies":

http://api.crossref.org/works?query=renear+-ontologies

Field Queries

Field queries are available on some routes and allow for queries that match only particular fields of metadata. For example, this query matches records that contain the tokens richard or feynman (or both) in any author field:

http://api.crossref.org/works?query.author=richard+feynman

Field queries can be combined with the general query paramter and each other. Each query parameter is ANDed with the others:

http://api.crossref.org/works?query.title=room+at+the+bottom&query.author=richard+feynman

/works Field Queries

These field queries are available on the /works route:

Field query parameter Description
query.title Query title and subtitle
query.container-title Query container-title aka. publication name
query.author Query author first and given names
query.editor Query editor first and given names
query.chair Query chair first and given names
query.translator Query translator first and given names
query.contributor Query author, editor, chair and translator first and given names

Sorting

Results from a listy response can be sorted by applying the sort and order parameters. Order sets the result ordering, either asc or desc. Sort sets the field by which results will be sorted. Possible values are:

Sort value Description
score or relevance Sort by relevance score
updated Sort by date of most recent change to metadata. Currently the same as deposited.
deposited Sort by time of most recent deposit
indexed Sort by time of most recent index
published Sort by publication date

An example that sorts results in order of publication, beginning with the least recent:

http://api.crossref.org/works?query=josiah+carberry&sort=published&order=asc

Facet Counts

Facet counts can be retrieved by enabling faceting; facet=t (or 1, true). Facet counts give counts per field value for an entire result set.

Filter Names

Filters allow you to narrow queries. All filter results are lists. The following filters are supported:

filter possible values description
has-funder metadata which includes one or more funder entry
funder {funder_id} metadata which include the {funder_id} in FundRef data
prefix {owner_prefix} metadata belonging to a DOI owner prefix {owner_prefix} (e.g. 10.1016 )
member {member_id} metadata belonging to a CrossRef member
from-index-date {date} metadata indexed since (inclusive) {date}
until-index-date {date} metadata indexed before (inclusive) {date}
from-deposit-date {date} metadata last (re)deposited since (inclusive) {date}
until-deposit-date {date} metadata last (re)deposited before (inclusive) {date}
from-update-date {date} Metadata updated since (inclusive) {date}. Currently the same as from-deposit-date.
until-update-date {date} Metadata updated before (inclusive) {date}. Currently the same as until-deposit-date.
from-created-date {date} metadata first deposited since (inclusive) {date}
until-created-date {date} metadata first deposited before (inclusive) {date}
from-pub-date {date} metadata where published date is since (inclusive) {date}
until-pub-date {date} metadata where published date is before (inclusive) {date}
has-license metadata that includes any <license_ref> elements.
license.url {url} metadata where <license_ref> value equals {url}
license.version {string} metadata where the <license_ref>'s applies_to attribute is {string}
license.delay {integer} metadata where difference between publication date and the <license_ref>'s start_date attribute is <= {integer} (in days)
has-full-text metadata that includes any full text <resource> elements.
full-text.version {string} metadata where <resource> element's content_version attribute is {string}.
full-text.type {mime_type} metadata where <resource> element's content_type attribute is {mime_type} (e.g. application/pdf).
public-references metadata where publishers allow references to be distributed publically. [^*]
has-references metadata for works that have a list of references
has-archive metadata which include name of archive partner
archive {string} metadata which where value of archive partner is {string}
has-orcid metadata which includes one or more ORCIDs
orcid {orcid} metadata where <orcid> element's value = {orcid}
issn {issn} metadata where record has an ISSN = {issn}. Format is xxxx-xxxx.
type {type} metadata records whose type = {type}. Type must be an ID value from the list of types returned by the /types resource
directory {directory} metadata records whose article or serial are mentioned in the given {directory}. Currently the only supported value is doaj.
doi {doi} metadata describing the DOI {doi}
updates {doi} metadata for records that represent editorial updates to the DOI {doi}
is-update metadata for records that represent editorial updates
has-update-policy metadata for records that include a link to an editorial update policy
container-title metadata for records with a publication title exactly with an exact match
publisher-name metadata for records with an exact matching publisher name
category-name metadata for records with an exact matching category label. Category labels come from this list published by Scopus
type-name metadata for records with an exacty matching type label
award.number {award_number} metadata for records with a matching award nunber. Optionally combine with award.funder
award.funder {funder doi or id} metadata for records with an award with matching funder. Optionally combine with award.number
assertion-group metadata for records with an assertion in a particular group
assertion metadata for records with a particular named assertion
affiliation metadata for records with at least one contributor with the given affiliation
has-affiliation metadata for records that have any affiliation information
alternative-id metadata for records with the given alternative ID, which may be a publisher-specific ID, or any other identifier a publisher may have provided
article-number metadata for records with a given article number

Multiple filters

Multiple filters can be specified in a single query. In such a case, different filters will be applied with AND semantics, while specifying the same filter multiple times will result in OR semantics - that is, specifying the filters:

  • is-update:true
  • from-pub-date:2014-03-03
  • funder:10.13039/100000001
  • funder:10.13039/100000050

would locate documents that are updates, were published on or after 3rd March 2014 and were funded by either the National Science Foundation (10.13039/100000001) or the National Heart, Lung, and Blood Institute (10.13039/100000050). These filters would be specified by joining each filter together with a comma:

/works?filter=is-update:true,from-pub-date:2014-03-03,funder:10.13039/100000001,funder:10.13039/100000050

Dot filters

A filter with a dot in its name is special. The dot signifies that the filter will be applied to some other record type that is related to primary resource record type. For example, with work queries, one can filter on works that have an award, where the same award has a particular award number and award-gving funding agency:

/works?filter=award.number:CBET-0756451,award.funder:10.13039/100000001

Here we filter on works that have an award by the National Science Foundation that also has the award number CBET-0756451.

Notes on owner prefixes

The prefix of a CrossRef DOI does NOT indicate who currently owns the DOI. It only reflects who originally registered the DOI. CrossRef metadata has an owner_prefix element that records the current owner of the CrossRef DOI in question.

CrossRef also has member IDs for depositing organisations. A single member may control multiple owner prefixes, which in turn may control a number of DOIs. When looking at works published by a certain organisaton, member IDs and the member routes should be used.

Notes on dates

Note that dates in filters should always be of the form YYYY-MM-DD, YYYY-MM or YYYY. Also note that date information in CrossRef metadata can often be incomplete. So, for example, a publisher may only include the year and month of publication for a journal article. For a monograph they might just include the year. In these cases the API selects the earliest possible date given the information provided. So, for instance, if the publisher only provided 2013-02 as the published date, then the date would be treated as 2013-02-01. Similarly, if the publisher only provided the year 2013 as the date, it would be treated at 2013-01-01.

Notes on incremental metadata updates

When using time filters to retrieve periodic, incremental metadata updates, the from-index-date filter should be used over from-update-date, from-deposit-date, from-first-deposit-date and from-pub-date. The timestamp that from-index-date filters on is guaranteed to be updated every time there is a change to metadata requiring a reindex.

Result controls

You can control the delivery and selection results using the rows, offset and sample parameters.

Rows

Normally, results are returned 20 at a time. You can control the number of results returns by using the rows parameter. To limit results to 5, for example, you could do the following:

http://api.crossref.org/works?query=allen+renear&rows=5

If you would just like to get the summary of the results, you can set the rows to 0 (zero).

http://api.crossref.org/works?query=allen+renear&rows=0

The maximum number rows you can ask for in one query is 1000.

Offset

The number of returned items is controlled by the rows parameter, but you can select the offset into the result list by using the offset parameter. So, for example, to select the second set of 5 results (i.e. results 6 through 10), you would do the following:

http://api.crossref.org/works?query=allen+renear&rows=5&offset=5

Deep Paging with Cursors

Using large offset values can result in extremely long response times. Offsets in the 100,000s and beyond will likely cause a timeout before the API is able to respond. An alternative to paging through very large result sets (like a corpus used for text and data mining) it to use the API's exposure of Solr's deep paging cursors. Any combination of query, filters and facets may be used with deep paging cursors. While rows may be specified along with cursor, offset and sample cannot be used. To use deep paging make a query as normal, but include the cursor parameter with a value of *. In this example we will page through all journal-article works from member 311:

http://api.crossref.org/members/311/works?filter=type:journal-article&cursor=*

A next-cursor field will be provided in the JSON response. To get the next page of results, pass the value of next-cursor as the cursor parameter:

http://api.crossref.org/members/311/works?filter=type:journal-article&cursor=AoE/CGh0dHA6Ly9keC5kb2kub3JnLzEwLjEwMDIvdGRtX2xpY2Vuc2VfMQ==

Clients should check the number of returned items. If the number of returned items is fewer than the number of expected rows then the end of the result set has been reached. Using next-cursor beyond this point will result in responses with an empty items list.

The cursor parameter is available on all /works resources.

Sample

Being able to select random results is useful for both testing and sampling. You can use the sample parameter to retrieve random results. So, for example, the following select 10 random works:

http://api.crossref.org/works?sample=10

Note that when you use the sample parameter, the rows and offset parameters are ignored.

Example Queries

All works published by owner prefix 10.1016 in January 2010

http://api.crossref.org/prefixes/10.1016/works?filter=from-pub-date:2010-01,until-pub-date:2010-01

All works funded by 10.13039/100000001 that have a CC-BY license

http://api.crossref.org/funders/10.13039/100000001/works?filter=license.url:http://creativecommons.org/licenses/by/3.0/deed.en_US

All works published by owner prefix 10.5555 from February 2010 to February 2013 that have a CC-BY license

http://api.crossref.org/prefixes/10.5555/works?filter=license.url:http://creativecommons.org/licenses/by/3.0/deed.en_US,from-pub-date:2010-02,until-pub-date:2013-02

All works funded by 10.13039/100000015 where license = CC-BY and embargo <= 365 days

http://api.crossref.org/funders/10.13039/100000015/works?filter=license.url:http://creativecommons.org/licenses/by/3.0/deed.en_US,license.delay:365

Note that the filters for license URL and maximum license embargo period (license.url and license.delay) combine to filter each document's metadata for a license with both of these properties.

All works where the archive partner listed = 'CLOCKSS'

http://api.crossref.org/works?filter=archive:CLOCKSS

All members with hind in their name (e.g. Hindawi)

http://api.crossref.org/members?query=hind

All licenses linked to works published by Elsevier

http://api.crossref.org/licenses?filter=member:78

All licenses applied to works published in the journal Pathology Research International

http://api.crossref.org/licenses?filter=issn:2090-8091

**All works with an award numbered roughly 1 F31 MH11745 also awarded by funder with ID 10.13039/100000025:

http://api.crossref.org/works?filter=award.number:1F31MH11745,award.funder:10.13039/100000025

Versioning

In theory, the syntax of the API can vary independently of the result representations. In practice, major version changes in either will require changes to API clients and so versioning of the API will apply to both the API syntax and the result representation.

The API uses a semantic versioning scheme whereby the version number is divided into three parts delimited by periods. The first number represents the "major" release number. The second represents a "minor" release number and the third represents an "internal" release number.

Version 1.20.31
        ^  ^  ^
        |  |  |
    major  |  |
       minor  |
       internal

Major version increments will are defined as releases that can break backwards compatibility. CrossRef will only commit to supporting the latest two major releases simultaneously and legacy major releases will be supported for no more than nine months. Exceptions to these rules may be made when major releases are required to ensure the security or stability of the system.

Minor version increments are defined as backwards compatible. There is no limit on the number of minor versions that can CrossRef can roll out. Note that client applications should not have dependencies on minor versions.

Internal version increments are simply used to keep track of development versions of the API. They should never have any effect on client applications.

Adding syntax options or metadata to representations will normally be backwards compatible and will thus normally only trigger minor version changes. Renaming or restructuring syntax options of metadata tends not to be backward compatible and will thus typically trigger major version changes

How to manage API versions

If you need to tie your implementation to a specific major version of the API, you can do so by using content-negotiation and specifying the version of the API in the ACCEPT header as follows:

 application/vnd.crossref-api-message+json; version=1.0

Minor version numbers will be ignored in ACCEPT headers as they are by definition backwards compatible.

If you omit a specific version in your ACCEPT header, the system will default to using the latest version of the API.

Note that requesting a version of the API via content type is not yet supported.

Error messages

There will be no errors, and therefor error messages will be unnecessary. But seriously… coming soon.