The source code from the free spigot/paperspigot plugin VPNCheck
This plugin is powered by http://proxycheck.io/ and its Java API (made by DefianceCoding https://github.com/DefianceCoding/PCDetectionAPI) The source code of this plugin is free to use in any of your projects, if you want you could also leave a small link to this page if you do use it (optional) If you need any assistance with the plugin or its code feel free to contact me over discord Great Array#4684
Have fun <3