
City, region and coordinates for 887,000+ postal codes across 95 countries.
PostalCodeCheck API is a free Geocoding API that requires no API key, is served over HTTPS and supports CORS, so it can be called from the browser.
Free JSON API for postal codes, ZIP codes and postcodes in 90+ countries. City, region and coordinates per code. No API key, 100 requests/day free.
Details from postalcodecheck.com.

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The PostalCodeCheck API is provided by PostalCodeCheck (postalcodecheck.com). Free JSON API for postal codes, ZIP codes and postcodes in 90+ countries. City, region and coordinates per code. No API key, 100 requests/day free.
Yes. The PostalCodeCheck API is listed in the Geocoding category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The PostalCodeCheck API requires no authentication, so you can start making requests without signing up.
Yes. The PostalCodeCheck API supports CORS, so front-end JavaScript can call it directly.
Yes. The PostalCodeCheck API is served over HTTPS, so it's safe to use in production.