Subdomain Scanner
Discover all subdomains for any domain using Certificate Transparency logs. Find hidden subdomains, check certificate validity, and export results.
Run a check to see results
POST /api/v1/dns/subdomainsKey Features
100% Free
No registration required, unlimited checks
Instant Results
Real-time analysis with detailed output
REST API Access
Integrate into your workflow via API
Accurate Data
Live queries to authoritative sources
What is Subdomain Scanner?
The Subdomain Scanner uses Certificate Transparency (CT) logs to discover subdomains associated with a domain. CT logs are public records of SSL/TLS certificates issued by certificate authorities. By querying these logs, the tool reveals subdomains that have had certificates issued for them — often exposing staging servers, internal tools, and forgotten infrastructure.
How to Use
- 1Enter the root domain you want to scan for subdomains
- 2Click 'Run Check' to query Certificate Transparency logs
- 3Browse the discovered subdomains, filter by name, and check certificate validity
- 4Export the results as CSV or copy all subdomains to clipboard
Who Uses This
System Administrators
Monitor and troubleshoot infrastructure
Developers
Debug network issues and integrate via API
SEO Specialists
Verify domain configuration and performance
Security Analysts
Audit and assess network security