Every .dk domain that delegates its _acme-challenge name to 931781b4-2a49-49bb-b50c-0b99f27a2b1c.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.