https://www.npmjs.com/package/maxmind-db
https://github.com/stefansundin/maxmind-db.js
Database specification: https://maxmind.github.io/MaxMind-DB/
React demo: https://github.com/stefansundin/maxmind-db.js/tree/react-demo
Installing a service worker makes this demo page available offline. You can also add the page to your home screen on certain platforms.
This product includes GeoLite2 data created by MaxMind, available from https://www.maxmind.com/.
If you make use of GeoLite2 in your product then according to the license you should include the statement above.
First you need to load a MaxMind database. By default the file will be cached in your web browser for use in later visits. You can also drag and drop an mmdb file on this page. Compressed databases (zip, tar, and gz) are also supported.
Then query it with IPv4 or IPv6 addresses.