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Keyvalue vs MailboxValidator Free Email Checker

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

APIKeyvalueHEALTHY79MailboxValidator Free Email CheckerHEALTHY94
Uptime · 30d
Uptime · 90d86.3%100%
Uptime · 30d80.0%100%
P50 · ms855527
P95 · ms20511138
AuthnoneapiKey
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree tier — API key required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Keyvalue vs MailboxValidator Free Email Checker: common questions

Which is more reliable, Keyvalue or MailboxValidator Free Email Checker?

On our scheduled checks, MailboxValidator Free Email Checker leads on measured uptime — Keyvalue at 86.3% versus MailboxValidator Free Email Checker at 100% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Which is faster, Keyvalue or MailboxValidator Free Email Checker?

MailboxValidator Free Email Checker has the lower median latency in our checks — Keyvalue responds in 855 ms versus MailboxValidator Free Email Checker at 527 ms (P50). Tail latency (P95) is in the table above; for most workloads the median is the number that shapes how the API feels.

Do Keyvalue and MailboxValidator Free Email Checker need an API key?

Keyvalue needs no key, while MailboxValidator Free Email Checker requires a free API key. If you want to start calling without signup, reach for Keyvalue first.

Can I call Keyvalue and MailboxValidator Free Email Checker from the browser?

Only Keyvalue 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 Keyvalue and MailboxValidator Free Email Checker free for commercial use?

Keyvalue 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.