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PM2.5 Open Data Portal vs Weather Underground API

Same instrument, two spec sheets — measured, not claimed.

APIPM2.5 Open Data PortalNEW—Weather Underground APIREACHABLE—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthnoneapiKey
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — no API keyFree tier — API key may be required for production
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

PM2.5 Open Data Portal vs Weather Underground API: common questions

Which is more reliable, PM2.5 Open Data Portal or Weather Underground API?

On our scheduled checks, Weather Underground API leads on measured uptime — PM2.5 Open Data Portal at —% versus Weather Underground API at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Do PM2.5 Open Data Portal and Weather Underground API need an API key?

PM2.5 Open Data Portal needs no key, while Weather Underground API requires a free API key. If you want to start calling without signup, reach for PM2.5 Open Data Portal first.

Can I call PM2.5 Open Data Portal and Weather Underground API from the browser?

Only Weather Underground API is browser-friendly — it returns CORS headers over HTTPS. PM2.5 Open Data Portal needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are PM2.5 Open Data Portal and Weather Underground API free for commercial use?

PM2.5 Open Data Portal has unclear commercial terms, and Weather Underground API has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.