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Census Bureau

Provider id census. Homepage: https://www.census.gov/

Access notes

The Census Data API requires a key on every data request. Checked on 2026-09-18: a keyless query, such as https://api.census.gov/data/2022/acs/acs5?get=NAME,B01003_001E&for=state:40, answers 302 to missing_key.html, which reads "A valid key must be included with each data API request", whatever the client, vintage, or dataset (ACS 5-year 2019 and 2022 and the 2020 decennial file were tried). Only the metadata is served without one: the dataset list at https://api.census.gov/data.json and variable definitions such as .../2022/acs/acs5/variables/B01003_001E.json. The API was previously usable without a key for light use, and an earlier version of the catalog entry said so.

That makes Census a credentialed source. Its geography is a state or county FIPS code (for=county:113&in=state:40), so it selects by place, not by box (ADR 0034). The ACS 5-year estimates are available, with their rules in ADR 0045.

This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau. The API terms ask every service that uses it to say so.

Checked with a key on 2026-09-27, against acs/acs5 vintages 2021 to 2023:

  • The response is a JSON array of arrays with a header row. Every value is a string, and the geography columns follow the requested variables. It holds no copy of the key, and identical requests return identical bytes.
  • A request takes at most fifty variables, NAME included; the fifty-first is 400 with error: 'get' is limited to 50 variables.
  • An unknown variable is 400 with a plain-text message, and an unknown vintage is a 404 HTML page. A missing or invalid key is a 302 to missing_key.html or invalid_key.html. A geography the vintage lacks is 204 with an empty body.
  • Connecticut is keyed by its eight old counties through vintage 2021 and by its nine planning regions from vintage 2022.
  • Margins of error and some estimates are negative annotation codes, such as -555555555 for a controlled estimate.

Datasets

See the generated dataset catalog for status, capabilities, endpoints, and versions.