dns-js is used to make a DNS query to find the TXT record for _esni.yourdomain.com.
The ESNI RFC requires the ESNI public keys to be available within the TXT record at this particular subdomain, making it a relatively effective method of checking a site for ESNI support.
dns-js is used to make a DNS query to find if an RRSIG record exists for yourdomain.com.
Node.js is used to attempt a connection to yourdomain.com while only allowing TLS 1.3.
The platform hosting Node.js seems to hang sometimes and may require a second button press.