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GrünstromIndex vs RainViewer

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

APIGrünstromIndexNEW—RainViewerNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified (attribution requested)
Free tierFree under fair-use policyFree — limits not published
Rate limitFair-use (paid tiers for higher limits)Unpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

GrünstromIndex vs RainViewer: common questions

Which is more reliable, GrünstromIndex or RainViewer?

On our scheduled checks, RainViewer leads on measured uptime — GrünstromIndex at —% versus RainViewer 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 GrünstromIndex and RainViewer need an API key?

Neither needs a paid key — GrünstromIndex is callable with no signup, and RainViewer is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call GrünstromIndex and RainViewer from the browser?

Yes — both GrünstromIndex and RainViewer send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.

Are GrünstromIndex and RainViewer free for commercial use?

GrünstromIndex has unclear commercial terms, and RainViewer 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.