Documentation for Crossref's REST API
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Crossref REST API

Note: Cited-by counts are up-to-date as of 2017-07-27


The Crossref REST API is one of a variety of tools and APIs that allow anybody to search and reuse our members' metadata in sophisticated ways.


Learning about performance or availability problems

Note that we generally post notice any ongoing performance problems with our services on our twitter feeds at CrossRefOrg and CrossRefSupport. We also report them on our support site. You might want to check these to see if we are already aware of a problem before you report it.

Reporting performance or availability problems

Report performance/availability at our support site.

Reporting bugs, requesting features

Please report bugs with the API or the documentation on our issue tracker.

Documentation License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Metadata 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.


We also have a privacy policy.


You might be able to avoid reading all this documentation if you instead use one of the several excellent libraries that have been written for the Crossref REST API. For example:

If you know of another library you would like to see listed here, please let us know about it via the issue tracker.


We want to provide a public, open, and free API for all. And we don't want to unnecessarily burden developers (or ourselves) with cumbersome API tokens or registration processes in order to use the public REST API. For that to work, we ask that you be polite and try not to do anything that will take the public REST API down or otherwise make it unusable for others. Specifically, we encourage the following polite behaviour:

  • Cache data so you don't request the same data over and over again.
  • Actively monitor API response times. If they start to go up, back-off for a while. For example, add pauses between requests and/or reduce the number of parallel requests.
  • Specify a User-Agent header that properly identifies your script or tool and that provides some type of means of contacting you. For example: GroovyBib/1.1 (; BasedOnFunkyLib/1.4.

This way we can contact you if we see a problem.

Alas, not all people are polite. And for this reason we reserve the right to impose rate limits and/or to block clients that are disrupting the public service.

Rate limits

From time to time Crossref needs to impose rate limits to ensure that the free API is usable by all. Any rate limits that are in effect will be advertised in the X-Rate-Limit-Limit and X-Rate-Limit-Interval HTTP headers.


This is always our last resort, and you can generally avoid it if you include contact information in the User-Agent header as described above.

But seriously... this is a bummer. We really want you to use the API. If you are polite about it, you shouldn't have any problems.

Use for production services

What if you want to use our API for a production service that cannot depend on the performance uncertainties of the free and open public API? What if you don't want to be affected by impolite people who do not follow the API Etiquette guidelines? Well, if you’re interested in using these tools or APIs for production services, we’ll soon have a service-level offering with access to all supported APIs and metadata, but with extra service and support guarantees. If you are interested in the upcoming service-based offering please contact our outreach team.

API overview

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

The API supports HTTP and HTTPS. Examples here are provided using HTTPS.

You should always url-encode DOIs and parameter values when using the API. DOIs are notorious for including characters that break URLs (e.g. semicolons, hashes, slashes, ampersands, question marks, etc.).

Note that, for the sake of clarity, the examples in this document do not url-encode DOIs or parameter values.

The API will only work for Crossref DOIs. You can test the registration agency for a DOI using the following route:{doi}/agency

Testing the following Crossref DOI:


Using the URL:

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.

Result types

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

  • Singletons
  • Headers-only
  • Lists

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


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

Headers only

You can use HTTP HEAD requests to quickly determine "existence" of a singleton. The advantage of this technique is that it is very fast because it does not return any metadata- it only retruns headers and an HTTP status code (200=exists, 404=does not exist).

To determine if member ID 98 exists:

curl --head ""

To determine if a journal with ISSN 1549-7712 exists:

curl --head ""


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 Funder 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 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 query terms
filter={filter_name}:{value} filter results by specific fields
rows={#} results per per page
offset={#} (mak 10k) result offset (user cursor for larger /works result sets)
sample={#} (max 100) return random N results
sort={#} sort results by a certain field
order={#} set the sort order to asc or desc
facet={#} enable facet information in responses
cursor={#} deep page through /works result sets

Multiple filters can be specified by separating name:value pairs with a comma:,from-pub-date:2004-04-04

Example query using URI parameters


Free form search queries can be made, for example, works that include renear and ontologies:

Field Queries

Field queries are available on the /works route 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:

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

/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 given and family names
query.editor Query editor given and family names
query.chair Query chair given and family names
query.translator Query translator given and family names
query.contributor Query author, editor, chair and translator given and family names
query.bibliographic Query bibliographic infomration, useful for citation look up. Includes titles, authors, ISSNs and publication years
query.affiliation Query contributor affiliations


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
published-print Sort by print publication date
published-online Sort by online publication date
issued Sort by issued date (earliest known publication date)
is-referenced-by-count Sort by number of references to documents
references-count Sort by number of references made by documents

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

Facet counts

Facet counts can be retrieved by enabling faceting. Facets are enabled by providing facet field names along with a maximum number of returned term values. The larger the number of returned values, the longer the query will take. Some facet fields can accept a * as their maximum, which indicates that all values should be returned.

Facets are specified with the facet parameter:*
Facet name Maximum values Description
affiliation * Author affiliation
year * Earliest year of publication, synonym for published
funder-name * Funder literal name as deposited alongside DOIs
funder-doi * Funder DOI
orcid 100 Contributor ORCID
container-title 100 Work container title, such as journal title, or book title
assertion * Custom Crossmark assertion name
archive * Archive location
update-type * Significant update type
issn 100 Journal ISSN (any - print, electronic, link)
published * Earliest year of publication
type-name * Work type name, such as journal-article or book-chapter
license * License URI of work
category-name * Category name of work
relation-type * Relation type described by work or described by another work with work as object
assertion-group * Custom Crossmark assertion group name

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
location {country_name} funder records where location = {country name}. Only works on /funders route
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}
from-online-pub-date {date} metadata where online published date is since (inclusive) {date}
until-online-pub-date {date} metadata where online published date is before (inclusive) {date}
from-print-pub-date {date} metadata where print published date is since (inclusive) {date}
until-print-pub-date {date} metadata where print published date is before (inclusive) {date}
from-posted-date {date} metadata where posted date is since (inclusive) {date}
until-posted-date {date} metadata where posted date is before (inclusive) {date}
from-accepted-date {date} metadata where accepted date is since (inclusive) {date}
until-accepted-date {date} metadata where accepted 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).
full-text.application {string} metadata where <resource> link has one of the following intended applications: text-mining, similarity-checking or unspecified
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
has-authenticated-orcid metadata which includes one or more ORCIDs where the depositing publisher claims to have witness the ORCID owner authenticate with ORCID
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
category-name metadata for records with an exact matching category label. Category labels come from this list published by Scopus
type metadata for records with type matching a type identifier (e.g. journal-article)
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
has-assertion metadata for records with any assertions
assertion-group metadata for records with an assertion in a particular group
assertion metadata for records with a particular named assertion
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
has-abstract metadata for records which include an abstract
has-clinical-trial-number metadata for records which include a clinical trial number
content-domain metadata where the publisher records a particular domain name as the location Crossmark content will appear
has-content-domain metadata where the publisher records a domain name location for Crossmark content
has-crossmark-restriction metadata where the publisher restricts Crossmark usage to content domains
has-relation metadata for records that either assert or are the object of a relation
relation.type One of the relation types from the Crossref relations schema (e.g. is-referenced-by, is-parent-of, is-preprint-of)
relation.object Relations where the object identifier matches the identifier provided
relation.object-type One of the identifier types from the Crossref relations schema (e.g. doi, issn)

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:


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:


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.

If you are expecting results beyond 10K, then use a cursor to deep page through the results. Note that not all routes support cursors.


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:

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

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


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:

Offsets for /works are limited to 10K. Use cursor (see below) for larger /works results sets.

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:*

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:

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.


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:

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,until-pub-date:2010-01

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

All works published by owner prefix 10.6064 from February 2010 to February 2013 that have a CC-BY license,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,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'

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

All licenses linked to works published by Elsevier*&filter=member:78&rows=0

All licenses applied to works published in the journal Pathology Research International*&filter=issn:2090-8091

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

API 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.

Version 1.20
        ^  ^
        |  |
    major  |

Major version increments 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 Crossref can roll out. Note that client applications should not have dependencies on minor versions, and Crossref will only maintain the latest minor version for the two most recent major versions.

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 version-specific routes. The default route redirects to the most recent version of the API. Some older major versions may be available using a version prefix. For example, to access version v1 of the API:


Each major version has no backwards incompatible changes within its public interface.

Documentation 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, 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
  • v30, 2016-09-26, highlight issue tracker
  • v31, 2016-10-05, document has-clinical-trial-number and has-abstract filters
  • v32, 2016-10-27, document rate limit headers
  • v33, 2016-11-07, guidance on when to use offset vs cursor
  • v34, 2017-04-26, document support for HTTPS. Update examples to use HTTPS.
  • v35, 2017-04-26, document use of head reqeusts to determine existence
  • v36, 2017-04-27, fixed license route examples to use facet/filter instead
  • v37, 2017-04-27, query.bibliographic
  • v38, 2017-04-27, add v1.1 filters and sort fields
  • v39, 2017-04-27, remove mention of dismax
  • v40, 2017-04-27, clarify faceting feature
  • v41, 2017-04-28, document sample max = 100, clarify cursors only work on some routes
  • v42, 2017-04-28, life, the universe, and everything
  • v43, 2017-04-28, reminder on the wisdom of url-encoding
  • v44, 2017-04-28, clarify that field queries apply to /works route
  • v45, 2017-04-28, document location filter for /funders route
  • v46, 2017-06-14, minor text changes and new funder registry link
  • v47, 2017-07-04, clarify query.affiliation
  • v48, 2017-07-13, correct "first and given" names to "given and family"
  • v49, 2017-07-20, move document version history, add section on libraries
  • v50, 2017-07-20, add TOC, move document history, add etiquet section, add production use section, general formatting + cleanup
  • v51, 2017-07-24, clarified license of the documentation (as opposed to metadata)
  • v52, 2017-07-27, removed service notice and what's new section.
  • v53, 2017-08-11, mention full-text.application filter