Every .dk domain that delegates its _acme-challenge name to 5a64e9c1-3990-483d-8a92-3d60b3619f3c.auth.acme-challenge.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.