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ISO 3166-2 API vs Postcodes.io

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

APIISO 3166-2 APINEW—Postcodes.ioNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedService MIT-licensed; postcode data license unverified
Free tierFree — limits not publishedFree — no key required
Rate limitUnpublishedUnpublished (no key; fair use)
In directory since2026-07-052026-07-05
operationalpartialdownno data

ISO 3166-2 API vs Postcodes.io: common questions

Which is more reliable, ISO 3166-2 API or Postcodes.io?

On our scheduled checks, Postcodes.io leads on measured uptime — ISO 3166-2 API at —% versus Postcodes.io 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 ISO 3166-2 API and Postcodes.io need an API key?

Neither needs a paid key — ISO 3166-2 API is callable with no signup, and Postcodes.io is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call ISO 3166-2 API and Postcodes.io from the browser?

Only Postcodes.io is browser-friendly — it returns CORS headers over HTTPS. ISO 3166-2 API needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are ISO 3166-2 API and Postcodes.io free for commercial use?

ISO 3166-2 API has unclear commercial terms, and Postcodes.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.