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Registrum API vs WhoisXML API Email Verification API

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

APIRegistrum APINEW—WhoisXML API Email Verification APINEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeyapiKey
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key requiredFree tier — API key required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Registrum API vs WhoisXML API Email Verification API: common questions

Which is more reliable, Registrum API or WhoisXML API Email Verification API?

On our scheduled checks, WhoisXML API Email Verification API leads on measured uptime — Registrum API at —% versus WhoisXML API Email Verification 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 Registrum API and WhoisXML API Email Verification API need an API key?

Both ask you to authenticate — Registrum API uses an API key and WhoisXML API Email Verification API uses an API key. Each key is free to obtain; the Auth and Card-required rows above spell out the signup terms.

Can I call Registrum API and WhoisXML API Email Verification API from the browser?

Only WhoisXML API Email Verification API 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 Registrum API and WhoisXML API Email Verification API free for commercial use?

Registrum API has unclear commercial terms, and WhoisXML API Email Verification 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.