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IsItWater vs SLF

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

APIIsItWaterNEW—SLFNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeynone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key requiredFree — static file, no key
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

IsItWater vs SLF: common questions

Which is more reliable, IsItWater or SLF?

On our scheduled checks, SLF leads on measured uptime — IsItWater 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 IsItWater and SLF need an API key?

SLF needs no key, while IsItWater requires a free API key. If you want to start calling without signup, reach for SLF first.

Can I call IsItWater and SLF from the browser?

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

Are IsItWater and SLF free for commercial use?

IsItWater 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.