How to mark sites that went through VPN?

Question

VPN

There is a VPS with VPN, at the moment SoftEther, but it doesn't matter.

A VPN connection is configured on the Keenetic router, and with the help of bird4, a cunning script allows blocked sites through the VPN, the list of blocked sites is taken here .

But suspicions crept into the correctness of the list.

Is it possible to mark sites that went through VPN somehow? Roughly speaking, before </body>inserting a script that will show a small popup.

Answer 1

https://habr.com/en/post/216295/