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The Guardian vs WhoisXML API Email Verification API

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

APIThe GuardianNEW—WhoisXML API Email Verification APINEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeyapiKey
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree developer key — registration requiredFree tier — API key required
Rate limit5000 calls/day (developer tier)Unpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

The Guardian vs WhoisXML API Email Verification API: common questions

Which is more reliable, The Guardian or WhoisXML API Email Verification API?

On our scheduled checks, WhoisXML API Email Verification API leads on measured uptime — The Guardian 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 The Guardian and WhoisXML API Email Verification API need an API key?

Both ask you to authenticate — The Guardian 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 The Guardian and WhoisXML API Email Verification API from the browser?

Yes — both The Guardian and WhoisXML API Email Verification API send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.

Are The Guardian and WhoisXML API Email Verification API free for commercial use?

The Guardian 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.