Library of Congress Collections API

openapi: 3.2.0
info:
  title: loc.gov JSON/YAML Collections API
  description: The loc.gov JSON/YAML API provides structured, machine-readable data about Library of Congress digital collections — books, photographs, maps, manuscripts, archived websites, videos, and more. No authentication is required. Responses are available in JSON or YAML format via the fo= query parameter.
  version: '1.0'
  contact:
    name: Library of Congress
    url: https://www.loc.gov/about/contact-us/
  license:
    name: U.S. Government Work
    url: http://www.loc.gov/text-us-government-work
servers:
- url: https://www.loc.gov
  description: Production server
tags:
- name: Collections
  description: Browse and access digital collections
paths:
  /collections/:
    get:
      tags:
      - Collections
      summary: List all digital collections
      description: Returns a list of all the digital collections at the Library of Congress. Collections are listed under the results attribute.
      operationId: listCollections
      parameters:
      - name: fo
        in: query
        description: Output format
        required: false
        schema:
          type: string
          enum:
          - json
          - yaml
        example: json
      - name: at
        in: query
        description: Limit response to specific attribute(s)
        required: false
        schema:
          type: string
        example: results
      - name: sp
        in: query
        description: Starting page number for pagination
        required: false
        schema:
          type: integer
          minimum: 1
      - name: c
        in: query
        description: Number of results per page
        required: false
        schema:
          type: integer
          minimum: 1
          maximum: 150
      responses:
        '200':
          description: List of digital collections
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SearchResponse'
  /collections/{collectionSlug}/:
    get:
      tags:
      - Collections
      summary: Get a specific digital collection
      description: Returns the web presentation of a specified digital collection in JSON format. The collection name must be in kebab-case (e.g., abraham-lincoln-papers or baseball-cards).
      operationId: getCollection
      parameters:
      - name: collectionSlug
        in: path
        description: 'URL slug for the collection (kebab-case, e.g., civil-war-maps, baseball-cards, abraham-lincoln-papers)

          '
        required: true
        schema:
          type: string
        example: civil-war-maps
      - name: fo
        in: query
        description: Output format
        required: false
        schema:
          type: string
          enum:
          - json
          - yaml
        example: json
      - name: at
        in: query
        description: Limit response to specific attribute(s)
        required: false
        schema:
          type: string
      - name: q
        in: query
        description: Search term to filter collection items
        required: false
        schema:
          type: string
      - name: fa
        in: query
        description: Facet filter
        required: false
        schema:
          type: string
      - name: sp
        in: query
        description: Starting page number for pagination
        required: false
        schema:
          type: integer
          minimum: 1
      - name: c
        in: query
        description: Number of results per page
        required: false
        schema:
          type: integer
          minimum: 1
          maximum: 150
      responses:
        '200':
          description: Collection data
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SearchResponse'
components:
  schemas:
    ItemSummary:
      type: object
      description: Summary information for a single collection item in search results
      properties:
        date:
          type: string
          description: Date associated with the item
        description:
          type: array
          items:
            type: string
          description: Descriptions of the item
        id:
          type: string
          description: URL identifier for the item (use to query the item endpoint)
        image_url:
          type: array
          items:
            type: string
          description: URLs for item thumbnail images
        index:
          type: integer
          description: Index position in results
        item:
          type: object
          description: Bibliographic metadata for the item
          additionalProperties: true
        language:
          type: array
          items:
            type: string
          description: Languages of the item
        location:
          type: array
          items:
            type: string
          description: Geographic locations associated with the item
        original_format:
          type: array
          items:
            type: string
          description: Original format types of the item
        partof:
          type: array
          items:
            type: string
          description: Collections or groups this item belongs to
        subject:
          type: array
          items:
            type: string
          description: Subject headings for the item
        title:
          type: string
          description: Title of the item
        type:
          type: array
          items:
            type: string
          description: Type classifications of the item
        url:
          type: string
          description: URL for the item's HTML page on loc.gov
    Pagination:
      type: object
      description: Pagination information for search results
      properties:
        count:
          type: integer
          description: Total number of items in the result set
        current:
          type: integer
          description: Current page number
        from:
          type: integer
          description: Index of the first item on the current page
        last:
          type: integer
          description: Index of the last item on the current page
        next:
          type:
          - string
          - 'null'
          description: URL for the next page of results
        of:
          type: integer
          description: Total number of pages
        perpage:
          type: integer
          description: Number of items per page
        previous:
          type:
          - string
          - 'null'
          description: URL for the previous page of results
        results:
          type: string
          description: Human-readable description of current result range
        to:
          type: integer
          description: Index of the last item on the current page
    FacetValue:
      type: object
      description: A facet value used to filter search results
      properties:
        count:
          type: integer
          description: Number of results matching this facet
        link:
          type: string
          description: URL to filter results by this facet value
        value:
          type: string
          description: The facet value text
    SearchResponse:
      type: object
      description: Standard search result response from the loc.gov JSON API
      properties:
        facets:
          type: object
          description: Available facets for filtering results
          additionalProperties:
            type: array
            items:
              $ref: '#/components/schemas/FacetValue'
        pagination:
          $ref: '#/components/schemas/Pagination'
        results:
          type: array
          description: List of collection items matching the query
          items:
            $ref: '#/components/schemas/ItemSummary'
externalDocs:
  description: API Documentation
  url: https://www.loc.gov/apis/json-and-yaml/