OpenAQ

Overview

OpenAQ aggregates open air-quality data from government and research sources worldwide — PM2.5, PM10, O₃, NO₂, CO, SO₂ and more — from thousands of monitoring stations. The v3 API requires a free API key (verified 2026-08: requests without a key return 401).

Quick Start

List locations (replace YOUR_KEY):

curl "https://api.openaq.org/v3/locations?limit=5" \
  -H "X-API-Key: YOUR_KEY"

Latest measurements for a location:

curl "https://api.openaq.org/v3/locations/2178/measurements/latest?limit=10" \
  -H "X-API-Key: YOUR_KEY"

Parameters (pollutants) catalog:

curl "https://api.openaq.org/v3/parameters?limit=100" \
  -H "X-API-Key: YOUR_KEY"

Authentication

• Register a free account at openaq.org and generate an API key.
• Send it as the X-API-Key header.

Rate Limits & Notes

• Free tier includes a daily request allowance (check the docs for current numbers).
• v3 API structure: locations, measurements, parameters, countries, cities — with pagination via limit/offset.
• Data is open-licensed and aggregated from official monitoring networks — good for dashboards and research.
• The legacy v2 API (/v2/) was keyless; v3 requires a key.

FAQ

Is OpenAQ free? Yes — free key with a daily request allowance.

Why do I get 401? The v3 API requires an API key via the X-API-Key header.

What data is available? Air-quality measurements (PM2.5, PM10, O₃, NO₂, CO, SO₂…) from thousands of stations worldwide.