OpenAQ

1. Base URL https://api.openaq.org, v3 paths, X-API-Key header, sign up at explore.openaq.org, key in settings, regenerable docs.openaq.org
2. Register at explore.openaq.org/register; key managed and rotated at explore.openaq.org/account; X-API-Key header docs.openaq.org
3. Free tier 60 req/min and 2,000 req/hour per key; custom use 'contact us for pricing' under a Custom Use Agreement; 429; rate-limit headers; repeated overruns may lead to ban docs.openaq.org
4. 403 means a blocked account or IP for terms violation or rate-limit abuse; needs manual intervention docs.openaq.org
5. coordinates (lat,lon) + radius max 25,000 m, bbox order, one method at a time, 422 restrictions docs.openaq.org
6. GET /v3/locations query parameters, defaults and 4-decimal precision cap docs.openaq.org
7. Endpoint paths and parameters (measurements/hours use datetime_from/datetime_to; days/years use date_from/date_to; latest takes datetime_min; flags endpoints); single APIKeyHeader security scheme api.openaq.org
8. Locations list provider, owner, instruments, sensors, licences with attribution and period; mobile coordinates are the first point measured docs.openaq.org
9. Latest endpoints /v3/locations/{id}/latest and /v3/parameters/{id}/latest; latest = last in series; out-of-order ingestion caveat docs.openaq.org
10. Sensor measurement endpoints (raw, hours, days, years), averaging rules, 408 timeout warning docs.openaq.org
11. Flags endpoint returns flag type label, level, time range and sensor ids per location docs.openaq.org
12. Licenses endpoint /v3/licenses/{id} and per-licence permission fields docs.openaq.org
13. Country labels from Natural Earth boundaries; may not label every station correctly docs.openaq.org
14. Bulk archive on AWS Open Data at openaq-data-archive, daily csv.gz per location docs.openaq.org
15. Official Python SDK and R package docs.openaq.org
16. Nonprofit; pollutants covered (PM2.5, PM10, SO2, NO2, CO, O3, BC, RH, temperature; limited PM1, PM4, CO2, NO, NOx, CH4, UFP); near real-time and historical; not all of the world's monitoring data; v1/v2 retired 31 Jan 2025 (410) docs.openaq.org
17. Free within rate limits; only openly licensed, stationary, ground-level data with coordinates and datetimes; acceptable frequency 10 min to 24 h; no satellite or airborne data; licence varies by source; attribute sources and OpenAQ; no guarantee data free of third-party claims; CORS blocked; Python SDK at python.openaq.org and R package at openaq.github.io/openaq-r docs.openaq.org
18. API key required for programmatic access; one key per individual; scraping forbidden, API use sanctioned; attribution to OpenAQ and sources; no-compete restriction on hosted API; higher limits need payment terms and API License and Services Agreement; as-is, no warranty; AI training, resale and ownership not mentioned docs.openaq.org
19. 'Hundreds of sources worldwide'; nonprofit openaq.org
20. Reference-grade government monitors since 2015, air sensors since 2021; registration required for API access openaq.org
21. 56,000 locations, 153 countries, 43 billion data points; sources are reference monitors and low-cost air sensors (OpenAQ slide deck, August 2024) haqast.wisc.edu
22. Third-party OpenAQ MCP servers (cyanheads, pipeworx-io, malamutemayhem); no first-party entry registry.modelcontextprotocol.io
23. Measurements carry the original value and period as reported upstream (datetimeFrom/datetimeTo) docs.openaq.org

About. Nonprofit aggregator of openly licensed, ground-level air-quality data from hundreds of sources worldwide (government reference monitors since 2015, low-cost air sensors since 2021), harmonized into one free REST API (api.openaq.org/v3) with near-real-time and historical measurements. It reports what existing stations publish; it cannot deploy new sensors.

Price. OpenAQ FAQ: data are provided for free within rate limits. The rate-limits page lists 'General use: Free' and 'Custom use: Contact us for pricing' for higher limits under a jointly agreed Custom Use Agreement. The terms say higher rates need OpenAQ's payment terms and API License and Services Agreement. No public price for custom plans.

Coverage. OpenAQ says it aggregates 'hundreds of sources worldwide' and that its data 'do not represent all air quality monitoring data in the world.' An OpenAQ slide deck from August 2024 cites 56,000 locations in 153 countries and 43 billion data points. Only stationary, ground-level data are ingested (no satellite or airborne data). Country labels come from Natural Earth boundaries and may mislabel some stations.

Timing. OpenAQ hosts 'near real-time and historical data'; acceptable source data frequency is between 10 minutes and 24 hours.

Licence. Varies by source. OpenAQ ingests only openly licensed data (e.g. CC0, CC BY 4.0) that it believes is available for redistribution, but gives no assurance the data are free of third-party claims; users must review and follow each source's terms (Creative Commons, open government or bespoke). Attribution to the original source where required, and to OpenAQ always, is required. Each location lists its licences, and the licences resource exposes commercialUseAllowed, attributionRequired, shareAlikeRequired, modificationAllowed and redistributionAllowed. Using the hosted API to build products that substantially duplicate or compete with OpenAQ is prohibited. Data are offered as-is without warranty. The terms do not mention AI training, resale or ownership of the data.