https://nodemaven.com/tools/dns-leak-test/
NodeMaven's Free DNS Leak Test is a simple, browser-based tool that exposes this hidden vulnerability. Run the test, and it analyzes your current DNS configuration, revealing which DNS servers your system is actually using. It checks for inconsistencies: if your proxy is based in Germany but your DNS queries are resolving through a server in your home country, you have a leak. If your ISP's DNS appears at all in the results, your DNS traffic is not protected. The tool shows you not just which DNS servers are being used, but also whether those queries are being transmitted over encrypted channels (DoH, DoT) or in plain text.