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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 PortalHEALTHY91Weather Underground APIREACHABLE100
Uptime · 30d
Uptime · 90d100%100%
Uptime · 30d100%100%
P50 · ms796104
P95 · ms13521117
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?

Both are neck-and-neck — PM2.5 Open Data Portal and Weather Underground API each measure 100% uptime over 90 days on our probe schedule. Reliability here is verified from our own scheduled checks; use the 30-day bars above to see which has been steadier lately.

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

Weather Underground API has the lower median latency in our checks — PM2.5 Open Data Portal responds in 796 ms versus Weather Underground API at 104 ms (P50). Tail latency (P95) is in the table above; for most workloads the median is the number that shapes how the API feels.

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.