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Callook.info vs Registrum API

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

APICallook.infoHEALTHY94Registrum APIHEALTHY96
Uptime · 30d
Uptime · 90d100%100%
Uptime · 30d100%100%
P50 · ms437246
P95 · ms11561553
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?

Both are neck-and-neck — Callook.info and Registrum 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, Callook.info or Registrum API?

Registrum API has the lower median latency in our checks — Callook.info responds in 437 ms versus Registrum API at 246 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 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.