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MailCheck.ai vs The SMS Works API

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

APIMailCheck.aiNEW—The SMS Works APINEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthnoneapiKey
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree tier — API key required
Rate limit5 req/window · 4 remainingUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

MailCheck.ai vs The SMS Works API: common questions

Which is more reliable, MailCheck.ai or The SMS Works API?

On our scheduled checks, The SMS Works API leads on measured uptime — MailCheck.ai at —% versus The SMS Works 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 MailCheck.ai and The SMS Works API need an API key?

MailCheck.ai needs no key, while The SMS Works API requires a free API key. If you want to start calling without signup, reach for MailCheck.ai first.

Can I call MailCheck.ai and The SMS Works API from the browser?

Yes — both MailCheck.ai and The SMS Works 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 MailCheck.ai and The SMS Works API free for commercial use?

MailCheck.ai has unclear commercial terms, and The SMS Works 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.