A maintained alternative to Zippopotam for postal codes

Zippopotam.us is a handy free postal-code lookup. If you want the same thing but maintained and sitting alongside country, city and IP data, countries.dev resolves postal/ZIP codes across 121 countries.

Resolve a postal code

curl https://countries.dev/postal/US/10001

[
  {
    "countryCode": "US",
    "postalCode": "10001",
    "placeName": "New York",
    "admin1": { "name": "New York", "code": "NY" },
    "latitude": 40.7484,
    "longitude": -73.9967,
    "accuracy": 4
  }
]

No key, and it works from the browser.

What each code gives you

The place name, administrative region (state/province) and district where available, coordinates, and an accuracy level — backed by GeoNames, ~1.8M codes across 121 countries. Browse the coverage on the postal code API page.

Switching over

Both are keyless GET-by-path. Zippopotam is /{country}/{zip}; countries.dev is /postal/{country}/{zip}. The response differs — countries.dev returns an array with placeName, admin1 and coordinates — so map the fields across.

See the postal code API demo, the docs, or how to autofill an address from a postal code.