Mexico Zip Codes API.
Postali 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.
Un curl. JSON limpio. Sin tarjeta, sin login, sin formulario.
Details from postali.app.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Provide geolocation data based on postcode for Dutch addresses
Brazilian postal codes (CEP) with IBGE coordinates, addresses and the companies registered there
The Postali API is provided by Postali (postali.app). Un curl. JSON limpio. Sin tarjeta, sin login, sin formulario.
Yes. The Postali 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 Postali API requires no authentication, so you can start making requests without signing up.
Yes. The Postali API supports CORS, so front-end JavaScript can call it directly.
Yes. The Postali API is served over HTTPS, so it's safe to use in production.