Free APIOpen DataAPI keyOfficial
U.S. Census Bureau Data API
ACS, decennial & economic census data down to the block group
The Census Data API gives programmatic access to hundreds of U.S. Census datasets: American Community Survey (ACS), decennial census, population estimates, and economic and business data, at nation/state/county/tract/block-group granularity. REST returning arrays-of-arrays JSON. A free API key is now required for all queries.
Free tier
Free key (required for all queries)Rate limits
A key is required on every request; per-key throttle is not publicly publishedAuth
API keyBase URL
https://api.census.gov/dataWhat you'd build with it
- Enrich a US address/zip with demographic and income data
- Build market-sizing or site-selection automations
- Map population, race, housing or income at tract/block-group level
- Resolve FIPS geography codes for downstream joins
Key endpoints
- GET
/{year}/acs/acs5?get={vars}&for={geo}&key={KEY}ACS 5-year estimates by geography - GET
/{year}/dec/pl?get={vars}&for={geo}&key={KEY}Decennial redistricting (PL 94-171) data - GET
/{year}/pep/population?get={vars}&for={geo}&key={KEY}Population estimates program - GET
/{year}/acs/acs5/variables.jsonVariable dictionary for a dataset
Members
Members get the runnable recipe
Sign in free to copy the example request, see a sample response, and read the gotchas.
Tags
demographicsgovernmentgeoopen-data