Every .dk domain that delegates its _acme-challenge name to be73625a-df76-4150-b3dd-e65cb2763850.acme-auth.itcn.dk. Such CNAMEs hand DNS-01 certificate validation to a shared service, so this list shows who issues TLS certificates through it. Data comes from our own scanners, which re-resolve every .dk domain in the zone roughly once a week.