Subdomain Finder
Discover subdomains for any domain — check common subdomain patterns and certificate transparency logs.
About Subdomain Finder
Subdomain enumeration is the process of finding all subdomains of a target domain. Subdomains often host different services (api.example.com, mail.example.com, staging.example.com) and can reveal attack surface, internal infrastructure, and forgotten services. Certificate Transparency (CT) logs record every TLS certificate issued, which often reveals subdomains — crt.sh provides a searchable interface to these logs.
FAQ
What is certificate transparency?
Certificate Transparency (CT) is a framework requiring all Certificate Authorities to log every TLS certificate they issue to public, append-only logs. This allows domain owners to detect unauthorized certificates and researchers to enumerate subdomains. Checking crt.sh for your domain regularly is a good security practice.