
Kakao Maps provide multiple APIs for Korean maps.
Kakao Maps API is a free Geocoding API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from apis.map.kakao.com.

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The Kakao Maps API is provided by Kakao 지도 API (apis.map.kakao.com).
Yes. The Kakao Maps 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.
Yes. The Kakao Maps API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Kakao Maps API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Kakao Maps API is served over HTTPS, so it's safe to use in production.