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Groundhog Day API vs PM2.5 Open Data Portal

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

APIGroundhog Day APINEW—PM2.5 Open Data PortalNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree — no API key
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Groundhog Day API vs PM2.5 Open Data Portal: common questions

Which is more reliable, Groundhog Day API or PM2.5 Open Data Portal?

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

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

Can I call Groundhog Day API and PM2.5 Open Data Portal from the browser?

Only Groundhog Day 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 Groundhog Day API and PM2.5 Open Data Portal free for commercial use?

Groundhog Day API has unclear commercial terms, and PM2.5 Open Data Portal 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.