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Postcodes.io vs What3Words

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

APIPostcodes.ioHEALTHY100What3WordsHEALTHY96
Uptime · 30d
Uptime · 90d100%100%
Uptime · 30d100%100%
P50 · ms33391
P95 · ms3281181
AuthnoneapiKey
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseService MIT-licensed; postcode data license unverifiedUnverified
Free tierFree — no key requiredFree tier — key may be required
Rate limitUnpublished (no key; fair use)Unpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Postcodes.io vs What3Words: common questions

Which is more reliable, Postcodes.io or What3Words?

Both are neck-and-neck — Postcodes.io and What3Words each measure 100% uptime over 90 days on our probe schedule. Reliability here is verified from our own scheduled checks; use the 30-day bars above to see which has been steadier lately.

Which is faster, Postcodes.io or What3Words?

Postcodes.io has the lower median latency in our checks — Postcodes.io responds in 33 ms versus What3Words at 391 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 Postcodes.io and What3Words need an API key?

Postcodes.io needs no key, while What3Words requires a free API key. If you want to start calling without signup, reach for Postcodes.io first.

Can I call Postcodes.io and What3Words from the browser?

Only Postcodes.io is browser-friendly — it returns CORS headers over HTTPS. What3Words needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are Postcodes.io and What3Words free for commercial use?

Postcodes.io has unclear commercial terms, and What3Words 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.