REST API filters
Records retrieved from the Crossref REST API can be filtered to give more precise results. On this page, we list and define the available filters for each available works endpoint. See here for more information about endpoints.
Filters are added using the filter parameter, with filters and values separated by a colon, and filters separated by a comma. For example:
https://api-crossref-org.ezproxy.galter.northwestern.edu/v1/works?filter=from-created-date:2023-04-01T12,until-created-date:2023-04-01T12
The journals, types, licenses, and members endpoints do not have filters. Other request parameters can be found in our Swagger documentation.
On this page
Below are filters for the following endpoints:
Members endpoint filters
The /members endpoint has the following filters:
| filter | value | description |
|---|
| backfile-doi-count | integer | members with given count of DOIs for material published more than two years ago. |
| current-doi-count | integer | members with given count of DOIs for material published within last two years . |
| prefix | string | members with given DOI prefix, e.g. 10.5555. |
Funders endpoint filters
| filter | description | |
|---|
| location | string | Funders located in the given country. |
Note that the country name is case sensitive, so location=France gives different results to location=france.
Works endpoint filters
The works endpoint has a very large number of filters. They can be used for any endpoint ending in works, for example members/works, journals/works, or works. We have broken then down into three types by function:
Filter by date
You can filter results for works before a certain date, after a certain date, or between two dates. Note that date ranges are inclusive so, for example, to get all metadata updated on a single day you can use the same day for the from and until filters, e.g.
https://api-crossref-org.ezproxy.galter.northwestern.edu/v1/works?filter=from-update-date:2025-10-01,until-update-date:2025-10-01
The following filters related to when metadata was received. ISO-formatted time stamps can be used with these filters. For example, any of the following are valid:
2025, 2025-01, 2025-01-04, 2025-01-04T00, 2025-01-04T00:12, 2025-01-04T00:12:32.
| filter | description |
|---|
| from-created-date | First deposited at or after the given date or time |
| until-created-date | First deposited before the given date or time |
| from-update-date | Deposited or redeposited at or after the given date or time, includes changes from the stewarding member |
| until-update-date | Deposited or redeposited at or before the given date or time, includes changes from the stewarding member |
| from-deposit-date | Deposited or redeposited at or after the given date or time (identical to from-update-date) |
| until-deposit-date | Deposited or redeposited on or before the given date or time (identical to until-update-date) |
| from-index-date | Reindexed in the API at or after the given date or time; includes changes from members, Crossref, and external sources. |
| until-index-date | Reindexed on or before the given date or time; includes changes from members, Crossref, and external sources. |
Date filters relating to the editorial and publication process. These and the following date filters take ISO-formatted dates as inputs, e.g. 2025, 2025-01, or 2025-01-05.
| filter | description |
|---|
| from-pub-date | The publication date is on or after the given date |
| until-pub-date | The publication date is on or before the given date |
| from-print-pub-date | Published in print on or after the given date |
| until-print-pub-date | Published in print on or before the given date |
| from-online-pub-date | Published online on or after the given date |
| until-online-pub-date | Published online date is on or before the given date |
| from-accepted-date | Accepted for publication on or after the given date |
| until-accepted-date | Accepted for publication on or before the given date |
| from-posted-date | Posted online on or after the given date, for the posted-content type |
| until-posted-date | Posted online on or before the given date, for the posted-content type |
| from-approved-date | Approved on or after the given date; for types dissertation, standard, and report |
| until-approved-date | Approved date is on or before the given date; for types dissertation, standard, and report |
| from-awarded-date | Awarded on or after the given date, for the grant type |
| until-awarded-date | Award on or before the given date, for the grant type |
Date filters related content items in a journal:
| filter | description |
|---|
| from-issued-date | Issued on or after the given date |
| until-issued-date | Issued on or before the given date |
Date filters related to content items in a conference:
| filter | description |
|---|
| from-event-start-date | Event start date is on or after the given date |
| until-event-start-date | Event start date is on or before the given date |
| from-event-end-date | Event end date is on or after the given date |
| until-event-end-date | Event end date is on or before the given date |
Find out whether a value is present
There are a number of filters that take a boolean value (0 or 1, true or false) that return content items that have a value in one or more metadata fields. For example:
https://api-crossref-org.ezproxy.galter.northwestern.edu/v1/works?filter=has-ror-id:1
The following filters relate to persistent identifiers:
| filter | identifier present (or not present) |
|---|
| has-orcid | ORCID ID |
| has-authenticated-orcid | ORCID ID where the ORCID owner has authenticated with ORCID (asserted by the depositing member) |
| has-clinical-trial-number | Clinical trial number |
| has-funder-doi | Funder DOI |
| has-ror-id | ROR ID |
| has-alias | The record has other DOIs aliased to it |
| has-prime-doi | The record has been aliased and redirects to another DOI |
The following filters return items with a given property (one or more times):
| filter | value present (or not present) |
|---|
| has-abstract | Abstract |
| has-description | A description field |
| has-license | One or more licenses for the content |
| has-update-policy | Contains a link to a policy describing how updates are made |
| has-domain-restriction | The member restricts content to speciffic domains (part of Crossmark) |
| has-assertion | Assertions (part of Crossmark) |
| has-content-domain | A content domain (part to Crossmark) |
These filters relate to presence of a relationship to another item or organisation
| filter | Relationship type |
|---|
| has-affiliation | has and author affiliated institution |
| has-award | was funded by an award |
| has-event | associated with an event |
| has-funder | includes a funder identifier (ROR or Funder ID) |
| has-relation | has any kind of relationship |
| has-update | has been updated by another DOI (e.g., via a correction or retraction) |
| is-update | is an update to another DOI (e.g., is a correction or retraction) |
| has-full-text | includes one or more full-text links |
| has-references | works that have a list of references |
| has-archive | includes the name of an archive partner |
Search for a specific value
These filters look for an exact match between the input value and the value in one or more fields in the metadata. If you’re looking across several fields, for values that contain a word or short phrase, or fuzzy matching , you can check the query parameters.
Apply these filters by provdiing the filter name and the value you would like to apply, for example to look for works in the serial with ISSN 1097-4547:
https://api-crossref-org.ezproxy.galter.northwestern.edu/v1/works?filter=issn:1097-4547
Filters related to identifiers
| filter | filter by the following metadata |
|---|
| alternative-id | Alternative ID, which may be a member-specific ID, or any other identifier a a member has provided |
| doi | The content item DOI |
| orcid | Contributor ORCID IDs |
| ror-id | Contributor affiliation or funding ROR IDs |
| isbn | The record’s ISBN |
| issn | The ISSN of the serial containing the item (e.g., 1234-5678) |
| member | Crossref member ID of the member who owns the record |
| prefix | the DOI owner prefix (e.g. 10.5555) |
Filters for metadata properties:
| filter | filter by the following metadata |
|---|
| article-number | Article number |
| group-title | Group title (used by content items of type posted-content) |
| license.url | License_ref is the given url |
| license.version | The license applies_to the given version (can be vor, am, tdm, or stm-asf) |
| license.delay | delay-in-days: how long after publication a license applies. The filter finds all values >= the given number |
| type | Metadata records whose type equals given type. Use one of the ID values in the /types endpoint |
| type-name | Type name. Use one of the name values in the /types endpoint |
| assertion | Name of an assertion (part of Crossmark) |
| assertion-group | Name of an assertion group (part of Crossmark) |
| content-domain | The domain name on which the content will appear (part of Crossmark) |
Filters related to funding metadata:
| filter | filter by the following metadata |
|---|
| award.funder | Award funder is the given funder |
| award.number | Award number is the given number |
| gte-award-amount | Award is greater than or equal to the given number |
| lte-award-amount | Award is less than or equal to the given number |
| funder | Funding metadata includes the given Funder ID |
| funder-doi-asserted-by | Funder DOI was asserted by the given body (crossref or publisher) |
Filters for relationships:
| filter | filter by the following metadata |
|---|
| archive | Archive partner has the given name |
| clinical-trial-number | Has the given clinical trial number |
| container-title | Container name (e.g., journal, conference, or book) exactly matches the given value |
| full-text.type | Resource element’s content_type attribute equals given version mime type (e.g., application/pdf) |
| full-text.application | Resource link has the given application (text-mining, similarity-checking or unspecified) |
| full-text.version | Resource element’s content_version attribute is the given version |
| relation.type | Has a relation with the given type (e.g., is-referenced-by, is-parent-of, is-preprint-of) |
| relation.object-type | Is related to an item of this type (e.g., doi, issn) |
| relation.object | Is related to the given identifier |
| update-type | Is an update of the given type (e.g., correction or retraction) |
| updates | Is an update to the given DOI |
