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IsItWater vs PostalCodes

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

APIIsItWaterNEW—PostalCodesNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeynone
CORSnono
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key requiredFree — limits not published
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

IsItWater vs PostalCodes: common questions

Which is more reliable, IsItWater or PostalCodes?

On our scheduled checks, PostalCodes leads on measured uptime — IsItWater at —% versus PostalCodes 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 IsItWater and PostalCodes need an API key?

PostalCodes needs no key, while IsItWater requires a free API key. If you want to start calling without signup, reach for PostalCodes first.

Can I call IsItWater and PostalCodes from the browser?

Neither sends browser-friendly CORS headers reliably, so call IsItWater and PostalCodes from a server or proxy rather than client-side. The CORS and HTTPS rows above show exactly what we detected for each.

Are IsItWater and PostalCodes free for commercial use?

IsItWater has unclear commercial terms, and PostalCodes 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.