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Callook.info vs Registrum API

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

APICallook.infoNEW—Registrum APINEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthnoneapiKey
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverified (data from public FCC ULS records)Unverified
Free tierFree — limits not publishedFree tier — API key required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Callook.info vs Registrum API: common questions

Which is more reliable, Callook.info or Registrum API?

On our scheduled checks, Registrum API leads on measured uptime — Callook.info at —% versus Registrum API 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 Callook.info and Registrum API need an API key?

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

Can I call Callook.info and Registrum API from the browser?

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

Are Callook.info and Registrum API free for commercial use?

Callook.info has unclear commercial terms, and Registrum 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.