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Numverify vs Userstack

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

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

Numverify vs Userstack: common questions

Which is more reliable, Numverify or Userstack?

On our scheduled checks, Userstack leads on measured uptime — Numverify at —% versus Userstack 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 Numverify and Userstack need an API key?

Both ask you to authenticate — Numverify uses an API key and Userstack 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 Numverify and Userstack from the browser?

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

Are Numverify and Userstack free for commercial use?

Numverify has unclear commercial terms, and Userstack 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.