Browsers verify the SCTs (in the certificate or less often as part of the TLS handshake). https://blog.pierky.com/certificate-transparency-manually-verify-sct-w

Browsers verify the SCTs (in the certificate or less often as part of the TLS handshake). https://blog.pierky.com/certificate-transparency-manually-verify-sct-with-openssl/ https://blog.pierky.com/certificate-transparency-manually-ve... This verification needs no communication between the browser/user-agent and the CT logs.