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PM2.5 Open Data Portal vs wttr.in

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

APIPM2.5 Open Data PortalNEW—wttr.inNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — no API keyFree — limits not published
Rate limitUnpublishedUnpublished (informal per-IP throttling)
In directory since2026-07-052026-07-05
operationalpartialdownno data

PM2.5 Open Data Portal vs wttr.in: common questions

Which is more reliable, PM2.5 Open Data Portal or wttr.in?

On our scheduled checks, wttr.in leads on measured uptime — PM2.5 Open Data Portal at —% versus wttr.in 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 wttr.in need an API key?

Neither needs a paid key — PM2.5 Open Data Portal is callable with no signup, and wttr.in is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call PM2.5 Open Data Portal and wttr.in from the browser?

Only wttr.in 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 wttr.in free for commercial use?

PM2.5 Open Data Portal has unclear commercial terms, and wttr.in 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.