specification: API Commons Rate Limits
specificationVersion: '0.1'
schema: https://raw.githubusercontent.com/api-evangelist/interface-research/main/schema/api-commons.yml#/$defs/RateLimits
provider: U.S. Census Bureau
providerId: us-census-bureau
created: '2026-05-25'
modified: '2026-05-25'
reconciled: false
tags:
- Government
- Open Data
- Rate Limiting
description: |
  The Census Bureau does not publish numeric request-per-minute / quota
  thresholds for the Census Data API, Microdata API, Geocoder, TIGERweb, or
  Population Clock. Operational guidance is qualitative — keys are free and
  one per email, and the Terms of Service note that the Bureau "reserves
  rights to monitor usage, block access for policy violations, modify terms
  unilaterally, and terminate service at its discretion." Heavy users are
  advised to batch via the Geocoder /addressbatch endpoint (up to 10,000
  addresses per request) and to spread the load over time.
sources:
- https://www.census.gov/data/developers/about/terms-of-service.html
- https://api.census.gov/data/key_signup.html
- https://www.census.gov/data/developers/guidance/api-user-guide.html
algorithm: undocumented
keys:
  required: true
  signupUrl: https://api.census.gov/data/key_signup.html
  placement: query
  parameter: key
  notes: One API key per email address. Keys are validated against the entire
    api.census.gov/data/* path family but not required for the public
    Population Clock JSON feed or for the Geocoder.
limits:
- endpoint: All /data/{vintage}/{dataset} endpoints
  perKey: undocumented
  perIp: undocumented
  notes: The user guide recommends batching variables in the `get` clause
    (up to 50 variables per request) and using `group(...)` to fetch entire
    tables in one call rather than per-variable queries.
- endpoint: /geocoder/locations/* and /geocoder/geographies/*
  perKey: not applicable
  perIp: undocumented
  notes: No API key required for the Geocoder. Server-side request timeouts
    apply; long-running single requests may be terminated.
- endpoint: /geocoder/locations/addressbatch and /geocoder/geographies/addressbatch
  perRequest: 10000 addresses
  perIp: undocumented
  notes: Multipart CSV upload; the Census Bureau publishes the 10,000-address
    limit per request in the Geocoding Services API user guide.
- endpoint: tigerweb.geo.census.gov/arcgis/rest/services/*
  perKey: not applicable
  perIp: undocumented
  notes: ArcGIS Server defaults apply; large feature-set queries may be
    truncated by the server-side `maxRecordCount` (typically 1,000-2,000
    features per page).
- endpoint: census.gov/popclock/data/*
  perKey: not applicable
  perIp: undocumented
  notes: Public JSON feed; recommended to cache client-side.
policies:
- name: Acceptable use
  description: Census data may not be used to identify any individual person,
    household, business, or other entity, alone or combined with other datasets.
- name: Attribution
  description: |
    Applications must display the disclaimer: "This product uses the Census
    Bureau Data API but is not endorsed or certified by the Census Bureau."
- name: Modified content
  description: Applications must not attribute modified Census Bureau content
    back to the Census Bureau.
- name: Key sharing
  description: Keys are issued per email; sharing is discouraged but not
    technically enforced.