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Abstract Email Validation vs Userstack

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

APIAbstract Email ValidationREACHABLE—UserstackNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeyapiKey
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — 100 requests/monthFree tier — API key required
Rate limit100 requests/month on free planUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Abstract Email Validation vs Userstack: common questions

Which is more reliable, Abstract Email Validation or Userstack?

On our scheduled checks, Userstack leads on measured uptime — Abstract Email Validation 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 Abstract Email Validation and Userstack need an API key?

Both ask you to authenticate — Abstract Email Validation 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 Abstract Email Validation and Userstack from the browser?

Yes — both Abstract Email Validation and Userstack 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 Abstract Email Validation and Userstack free for commercial use?

Abstract Email Validation 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.