DNS leak allows the site to detect the DNS resolver that the user is accessing.
In most cases, the IP address of the DNS resolver can be used to identify the internet provider that the resource visitor is using.
Sometimes the user's router can work as a DNS resolver — then DNS leak is possible to identify the user's IP address directly.
If you are connected to a VPN service that does not protect against DNS leak, then the visited resource can at least identify the internet operator through which you are connected, but less often your IP address directly.Red Shiled VPN protects against DNS leak: our VPN servers run their own DNS resolvers, and VPN applications allow the device to access only our DNS resolver.
You can check for a DNS leak on the website dnsleaktest.com: if, being connected to our VPN, you see the IP address of our server in the test results, then the leakage protection works.