
Get all administrative divisions of a country.
administrative-divisons-db 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.
Administrative regions as a JSON API over Github/Cloudflare CDN
Details from github.com.

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The administrative-divisons-db API is provided by kamikazechaser (github.com). Administrative regions as a JSON API over Github/Cloudflare CDN
Yes. The administrative-divisons-db 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 administrative-divisons-db API requires no authentication, so you can start making requests without signing up.
Yes. The administrative-divisons-db API supports CORS, so front-end JavaScript can call it directly.
Yes. The administrative-divisons-db API is served over HTTPS, so it's safe to use in production.