CertObserver is a search engine for Certificate Transparency (CT) logs.
Key Features
- Real-time indexing: New certificates typically appear within 10 minutes of issuance by a Certificate Authority.
- Granular search scopes: Supports exact DNS SAN matches, host coverage (including wildcards), and recursive subdomain searches.
- Advanced filtering: Group results by SAN sets, issuer organizations, or Subject Public Key Info (SPKI) for deeper analysis.
- Accessibility: Provides a fast, free interface without the need for accounts or API keys.
Use Cases
- Passive subdomain discovery for penetration testing and bug bounty engagements.
- Identifying shadow IT and forgotten staging environments through certificate metadata.
- Monitoring target domains for rogue or unauthorized certificate issuance in real-time.
