find_apisBrowse and filter every API in the catalog.
get_api_artifactsOne API's artifacts, grouped by type.
get_openapiThe primary OpenAPI for this API.
find_similar_apisAPIs that look like this one.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

All 92 tools

Call it yourself

curl for this page

This API

curl "https://apis.io/api/v1/apis/opencitations-metadata-api"

All apis

curl "https://apis.io/api/v1/apis?limit=25"

Discovery needs no key. Ratings and market analysis are Pro.

Get an API key

Free tier, no email required.

GitHub Google LinkedIn

A second provider on the same verified email joins the account you already have.

OpenAPI Specification

openapi: 3.0.3
info:
  title: OpenCitations Index REST Authors Metadata API
  description: 'REST API for accessing the data stored in the OpenCitations Index. Provides operations to retrieve citation data for references to other works appearing in a particular bibliographic entity, or citation data for references in other works to a particular bibliographic entity, given the identifier of a bibliographic entity, or to retrieve citation data about a particular citation identified by means of its Open Citation Identifier (OCI).

    All operations return either a JSON document (default) or a CSV document according to the mimetype specified in the Accept header of the request.

    API calls are rate-limited to 180 requests/minute per IP address. For large-scale retrieval use the database dumps at download.opencitations.net.

    '
  version: 2.2.0
  contact:
    name: OpenCitations
    email: contact@opencitations.net
    url: https://opencitations.net
  license:
    name: Creative Commons Attribution 4.0 International
    url: https://creativecommons.org/licenses/by/4.0/legalcode
  x-api-created: '2025-04-15'
servers:
- url: https://api.opencitations.net/index/v2
  description: OpenCitations Index API v2
security:
- accessToken: []
- {}
tags:
- name: Metadata
  description: Operations for retrieving bibliographic metadata
paths:
  /metadata/{ids}:
    get:
      summary: Get bibliographic metadata by ID
      operationId: getMetadataByIds
      description: 'Retrieves the bibliographic metadata for each of the bibliographic entities identified by one or more input IDs.

        Each ID is built as follows: ID abbreviation + ":" + ID value. For example, "doi:10.3233/ds-170012" indicates a DOI identifier with value "10.3233/ds-170012".

        Supported ID abbreviations: doi, issn, isbn, omid, openalex, pmid, pmcid.

        Multiple IDs can be specified separated with double underscore "__". Example: doi:10.1108/jd-12-2013-0166__doi:10.1016/j.websem.2012.08.001

        Fields returned: - id: the IDs of the bibliographic entity (space-separated) - title: the title of the bibliographic entity - author: semicolon-separated list of authors - pub_date: date of publication - venue: title of the venue with identifiers - volume: volume number - issue: issue number - page: starting and ending pages - type: type of bibliographic entity - publisher: publisher with identifiers - editor: semicolon-separated list of editors

        '
      tags:
      - Metadata
      parameters:
      - name: ids
        in: path
        required: true
        description: 'One or more bibliographic entity IDs separated by "__". Supported prefixes: doi, issn, isbn, omid, openalex, pmid, pmcid.

          '
        schema:
          type: string
          example: doi:10.1007/978-1-4020-9632-7
      - $ref: '#/components/parameters/require'
      - $ref: '#/components/parameters/filter'
      - $ref: '#/components/parameters/sort'
      - $ref: '#/components/parameters/format'
      - $ref: '#/components/parameters/json'
      responses:
        '200':
          description: Bibliographic metadata records
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/BibliographicMetadata'
              example:
              - id: doi:10.1007/978-1-4020-9632-7 isbn:9781402096327 isbn:9789048127108 openalex:W4249829199 omid:br/0612058700
                title: Adaptive Environmental Management
                author: ''
                pub_date: '2009'
                page: ''
                issue: ''
                volume: ''
                venue: ''
                type: book
                publisher: Springer Science And Business Media Llc [crossref:297 omid:ra/0610116006]
                editor: Allan, Catherine [orcid:0000-0003-2098-4759 omid:ra/069012996]; Stankey, George H. [omid:ra/061808486861]
            text/csv:
              schema:
                type: string
        '404':
          description: No metadata found for the given IDs
components:
  schemas:
    BibliographicMetadata:
      type: object
      description: Bibliographic metadata for a scholarly work
      properties:
        id:
          type: string
          description: 'Space-separated list of identifiers for the bibliographic entity. May include doi, isbn, issn, openalex, omid, pmid, pmcid values.

            '
          example: doi:10.1007/978-1-4020-9632-7 isbn:9781402096327 omid:br/0612058700
        title:
          type: string
          description: Title of the bibliographic entity
          example: Adaptive Environmental Management
        author:
          type: string
          description: 'Semicolon-separated list of authors with their identifiers in brackets. Format: FamilyName, GivenName [orcid:... omid:ra/...]

            '
          example: Peroni, Silvio [orcid:0000-0003-0530-4305 omid:ra/0610122312]
        pub_date:
          type: string
          description: Publication date (ISO 8601 or partial date)
          example: '2009'
        issue:
          type: string
          description: Issue number of the publication
          example: '1'
        volume:
          type: string
          description: Volume number of the publication
          example: '42'
        venue:
          type: string
          description: Title of the publication venue with identifiers in brackets
          example: Scientometrics [issn:0138-9130 omid:br/0612058701]
        page:
          type: string
          description: Starting and ending page numbers
          example: 1-25
        type:
          type: string
          description: Type of the bibliographic entity
          enum:
          - book
          - book chapter
          - book part
          - book section
          - book series
          - book set
          - book track
          - component
          - dataset
          - dissertation
          - edited book
          - journal
          - journal article
          - journal issue
          - journal volume
          - monograph
          - other
          - peer review
          - posted content
          - proceedings
          - proceedings article
          - proceedings series
          - reference book
          - reference entry
          - report
          - report series
          - standard
          - standard series
          example: book
        publisher:
          type: string
          description: Publisher name with identifiers in brackets
          example: Springer Science And Business Media Llc [crossref:297 omid:ra/0610116006]
        editor:
          type: string
          description: 'Semicolon-separated list of editors with their identifiers in brackets. Format: FamilyName, GivenName [orcid:... omid:ra/...]

            '
          example: Allan, Catherine [orcid:0000-0003-2098-4759 omid:ra/069012996]
  parameters:
    filter:
      name: filter
      in: query
      required: false
      description: 'Applies conditional filtering. Supports regex or operators (=, <, >). Format: field:operator:value. Example: date:>2015

        '
      schema:
        type: string
        example: date:>2015
    format:
      name: format
      in: query
      required: false
      description: Output format. Accepts "csv" or "json" (default).
      schema:
        type: string
        enum:
        - json
        - csv
        default: json
    sort:
      name: sort
      in: query
      required: false
      description: 'Orders results by field in ascending or descending order. Format: asc(field) or desc(field).

        '
      schema:
        type: string
        example: desc(pub_date)
    json:
      name: json
      in: query
      required: false
      description: 'Transforms JSON data structure. Supports array splitting or dict conversion.

        '
      schema:
        type: string
    require:
      name: require
      in: query
      required: false
      description: Removes rows with empty values in the specified field
      schema:
        type: string
        example: doi
  securitySchemes:
    accessToken:
      type: apiKey
      in: header
      name: authorization
      description: 'OpenCitations Access Token obtained from https://opencitations.net/accesstoken. Recommended for application/code usage to ensure stable access.

        '
externalDocs:
  description: OpenCitations Index API Documentation
  url: https://api.opencitations.net/index/v2