It can be anything! An apex, subdomain, or even a URL.

Results forww25.server.nullsecurity.site

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2025-10-06T07:01:30.534	2025-10-06T06:02:58	2026-01-04T06:02:57	ww25.server.nullsecurity.site	ww25.server.nullsecurity.site	C=US, O=Let's Encrypt, CN=R13
2025-10-06T07:01:28.37	2025-10-06T06:02:58	2026-01-04T06:02:57	ww25.server.nullsecurity.site	ww25.server.nullsecurity.site	C=US, O=Let's Encrypt, CN=R13
2025-01-11T15:25:18.687	2025-01-11T14:26:48	2025-04-11T14:26:47	ww25.server.nullsecurity.site	ww25.server.nullsecurity.site	C=US, O=Let's Encrypt, CN=R10
2025-01-11T15:25:18.416	2025-01-11T14:26:48	2025-04-11T14:26:47	ww25.server.nullsecurity.site	ww25.server.nullsecurity.site	C=US, O=Let's Encrypt, CN=R10
2024-10-09T03:24:59.163	2024-10-09T02:26:28	2025-01-07T02:26:27	ww25.server.nullsecurity.site	ww25.server.nullsecurity.site	C=US, O=Let's Encrypt, CN=R11
2024-10-09T03:24:58.775	2024-10-09T02:26:28	2025-01-07T02:26:27	ww25.server.nullsecurity.site	ww25.server.nullsecurity.site	C=US, O=Let's Encrypt, CN=R11