# curl -I https://acme-v02.api.letsencrypt.org/directory
HTTP/2 200
server: nginx
date: Mon, 15 Feb 2021 13:36:21 GMT
content-type: application/json
content-length: 658
cache-control: public, max-age=0, no-cache
replay-nonce: 0104cpQyyC070fhhCXeGGjiL46q2B58VL70j1HDj7e1pAPc
x-frame-options: DENY...