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Open Topo Data vs SLF

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

APIOpen Topo DataNEW—SLFNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree — static file, no key
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Open Topo Data vs SLF: common questions

Which is more reliable, Open Topo Data or SLF?

On our scheduled checks, SLF leads on measured uptime — Open Topo Data at —% versus SLF 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 Open Topo Data and SLF need an API key?

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

Can I call Open Topo Data and SLF from the browser?

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

Are Open Topo Data and SLF free for commercial use?

Open Topo Data has unclear commercial terms, and SLF 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.