[helb]

JS does a GET request every 2 seconds or so to some random subdomain (probably to avoid caching): https://i.vgy.me/qCTabA.png

The JSON response contains 'status: "unconfigured"' when you're not using their resolver and 'status: "ok"' when you are: https://i.vgy.me/iVgIe1.png

That green bar just appears after a "ok" response (no page reload needed).

[ignoramous]

Here's an open source nameserver that helps ID DNS resolver in use: https://github.com/redirect2me/which-dns

[ulti552]

stupid q here but what font is your terminal using from your screenshot pic

[helb]

Iosevka: https://typeof.net/Iosevka/