crt.sh
About crt.sh
crt.sh is a free Certificate Transparency log search engine operated by Sectigo that enables users to search for SSL/TLS certificates issued for any domain. The platform indexes certificates from all major CT logs, providing subdomain discovery, certificate chain verification, and issuer tracking. Security researchers use crt.sh to discover hidden subdomains via certificate SANs, monitor for unauthorized certificate issuance, and track phishing domains using similar certificate patterns. Essential tool in the OSINT and reconnaissance toolkit.
Why Notable
CT log search by Sectigo; subdomain discovery via cert SANs; monitors unauthorized issuance
