Free Certificate Transparency Checker & Subdomain Finder
Discover hidden subdomains and monitor SSL certificates through Certificate Transparency logs. Find forgotten infrastructure, detect unauthorized certificate issuance, analyze CT logs, and map your complete attack surface for free.
Subdomain Discovery
Find all subdomains by analyzing Certificate Transparency logs
Certificate Monitoring
Track all SSL certificates issued for your domain and subdomains
CA Analysis
Identify all Certificate Authorities that have issued certificates
Historical Data
View historical certificate issuance and track changes over time
What Certificate Transparency Reveals
Certificate Information
- All SSL certificates issued for your domain
- Certificate issuance timestamps
- Issuing Certificate Authorities (CAs)
- Certificate serial numbers and validity periods
Subdomain Discovery
- Hidden subdomains not in DNS
- Historical subdomains and infrastructure
- Development and staging environments
- Recently added or removed subdomains
Security Insights
- Detect unauthorized certificate issuance
- Identify unusual certificate patterns
- Monitor for rogue or wildcard certificates
- Track certificate authority changes
Attack Surface Analysis
- Map your entire domain infrastructure
- Discover forgotten or abandoned subdomains
- Identify potential security exposure
- Audit your certificate management
About Certificate Transparency
Certificate Transparency (CT) is an internet security standard that provides an open framework for monitoring and auditing SSL/TLS certificates. Every publicly trusted certificate is logged in append-only CT logs that anyone can query.
CT logs are invaluable for:
- Subdomain Discovery: Find all subdomains by searching CT logs for certificates
- Security Monitoring: Detect unauthorized or suspicious certificate issuance
- Certificate Management: Track all certificates across your infrastructure
- Compliance: Audit certificate issuance for regulatory compliance
- Threat Intelligence: Identify potential phishing domains targeting your brand
Common Use Cases
Security Teams
- Monitor for unauthorized certificates
- Discover shadow IT infrastructure
- Detect phishing attempts using similar domains
- Audit certificate authority selection
Bug Bounty Hunters
- Find hidden subdomains for testing
- Discover development/staging servers
- Identify forgotten infrastructure
- Map the complete attack surface
DevOps Teams
- Track certificate lifecycle
- Identify expiring certificates
- Audit infrastructure inventory
- Monitor certificate deployment
Certificate transparency questions
What is certificate transparency?
A public, append-only record of TLS certificates issued by public certificate authorities. Browsers require new certificates to be logged, so anyone can see which certificates exist for a domain.
Why check my domain's CT logs?
To spot certificates you did not request, which can mean a mis-issuance or an attacker preparing to impersonate you, and to find subdomains you had forgotten about.
Can CT logs reveal my subdomains?
Yes. Every hostname on a public certificate is visible in the logs, including staging and internal names. Attackers use this to find forgotten systems, so it is worth seeing what they see.
What should I do about an unexpected certificate?
Find out who requested it. If nobody on your team did, contact the issuing certificate authority to have it revoked, and add a CAA record so only the CAs you use can issue certificates.
Is the certificate transparency checker free?
Yes, with no registration. It searches public CT log data.
This is one check. A full scan runs them all.
FreeThe Certificate Transparency Check covers one area. A full scan runs every check on the same site in one go, so nothing it does not reach goes unnoticed.
Covered by this check
- Subdomain discovery via CT logs
- Certificate issuance monitoring
- Certificate Authority analysis
- Historical certificate tracking
- Unauthorized certificate detection
Added by a full scan
- SSL/TLS certificate validation
- Security headers analysis
- WordPress vulnerability scanning
- Malware & script detection
- DNS security (DNSSEC, CAA)
- Domain reputation analysis
- Port scanning
- And 6+ more security checks
Want it checked automatically? A free account rescans one site every week and emails you new findings. No credit card.
Start free monitoringMore domain and infrastructure tools
Subdomain Finder
Discover subdomains for any domain using Certificate Transparency logs.
SSL Certificate Checker
Validate the certificate, chain and expiry of any site.
WHOIS Lookup
Look up domain registration, registrar and nameserver details.
DNS Lookup
Look up A, AAAA, MX, TXT, NS and other DNS records for any domain.