External
crt.sh
Search every TLS certificate ever logged for a domain.
crt.sh, operated by Sectigo, searches Certificate Transparency logs, showing every certificate publicly issued for a domain. It is free and widely used for security research, subdomain discovery and verifying what certificates exist in your name.
Best for: Use this when you want to audit which certificates, and therefore hostnames, exist for a domain.
Pros
- Complete view sourced from public CT logs
- Great for spotting unexpected or forgotten certificates
- Free with no account
Cons
- Frequently slow or briefly unavailable under load
- Raw, research-grade interface
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