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Acoustid API vs MailboxValidator Free Email Checker

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

APIAcoustid APINEW—MailboxValidator Free Email CheckerNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeyapiKey
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key may be required for productionFree tier — API key required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Acoustid API vs MailboxValidator Free Email Checker: common questions

Which is more reliable, Acoustid API or MailboxValidator Free Email Checker?

On our scheduled checks, MailboxValidator Free Email Checker leads on measured uptime — Acoustid API at —% versus MailboxValidator Free Email Checker 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 Acoustid API and MailboxValidator Free Email Checker need an API key?

Both ask you to authenticate — Acoustid API uses an API key and MailboxValidator Free Email Checker 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 Acoustid API and MailboxValidator Free Email Checker from the browser?

Only Acoustid API is browser-friendly — it returns CORS headers over HTTPS. MailboxValidator Free Email Checker needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are Acoustid API and MailboxValidator Free Email Checker free for commercial use?

Acoustid API has unclear commercial terms, and MailboxValidator Free Email Checker 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.