Graph Countries
Country-related data like currencies, languages, flags, regions+subregions and bordering countries

IP geolocation, ISP and privacy/VPN scoring, email breach checks, DNS and WHOIS lookups.
HackMyIP 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 public REST API: IP geolocation, VPN/proxy detection, email breach check, DNS & WHOIS. No API key, no signup. 10 endpoints, JSON, CORS-enabled.
Details from hackmyip.com.

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.
Country-related data like currencies, languages, flags, regions+subregions and bordering countries
Ip to location with country code, currency code & currency name, fast response, unlimited requests
The HackMyIP API is provided by HackMyIP (hackmyip.com). Free public REST API: IP geolocation, VPN/proxy detection, email breach check, DNS & WHOIS. No API key, no signup. 10 endpoints, JSON, CORS-enabled.
Yes. The HackMyIP 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 HackMyIP API requires no authentication, so you can start making requests without signing up.
Yes. The HackMyIP API supports CORS, so front-end JavaScript can call it directly.
Yes. The HackMyIP API is served over HTTPS, so it's safe to use in production.