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MailboxValidator Free Email Checker vs Nationalize.io

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

APIMailboxValidator Free Email CheckerHEALTHY94Nationalize.ioHEALTHY93
Uptime · 30d
Uptime · 90d100%97.1%
Uptime · 30d100%100%
P50 · ms527448
P95 · ms1138985
AuthapiKeynone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key requiredKeyless usage limited (x-rate-limit-limit: 25 observed); 2,500 names/mo with a free key
Rate limitUnpublishedKeyless cap 25 per x-rate-limit-limit header; remaining/reset exposed in response headers
In directory since2026-07-052026-07-05
operationalpartialdownno data

MailboxValidator Free Email Checker vs Nationalize.io: common questions

Which is more reliable, MailboxValidator Free Email Checker or Nationalize.io?

On our scheduled checks, MailboxValidator Free Email Checker leads on measured uptime — MailboxValidator Free Email Checker at 100% versus Nationalize.io at 97.1% 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, MailboxValidator Free Email Checker or Nationalize.io?

Nationalize.io has the lower median latency in our checks — MailboxValidator Free Email Checker responds in 527 ms versus Nationalize.io at 448 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 MailboxValidator Free Email Checker and Nationalize.io need an API key?

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

Can I call MailboxValidator Free Email Checker and Nationalize.io from the browser?

Only Nationalize.io 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 MailboxValidator Free Email Checker and Nationalize.io free for commercial use?

MailboxValidator Free Email Checker has unclear commercial terms, and Nationalize.io 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.