Free Subdomain Scanner (OSINT) Online
Discover hidden subdomains for a target domain using public OSINT certificate databases.
This scan queries public Certificate Transparency (CT) logs. It may take up to 10 seconds.
Discovered Subdomains for:
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Free Online Subdomain Scanner (OSINT)
Our Subdomain Scanner is an advanced Open-Source Intelligence (OSINT) tool built for ethical hackers, penetration testers, and bug bounty hunters. It helps you map out a target's external attack surface by discovering hidden or forgotten subdomains associated with the primary domain.
How It Works (Certificate Transparency)
Unlike brute-force tools that guess subdomain names, this tool queries Certificate Transparency (CT) logs (such as crt.sh). Whenever a Certificate Authority issues an SSL/TLS certificate for a domain or subdomain, it is publicly logged. By analyzing these logs, we can instantly pull a highly accurate list of subdomains without sending a single packet to the target server.
Why Map Subdomains?
- Vulnerability Discovery: Forgotten subdomains (like
dev.example.comorstaging.example.com) often host outdated software, debug interfaces, or exposed APIs that are ripe for exploitation. - Subdomain Takeover: Finding subdomains pointing to unclaimed third-party services (like GitHub Pages, AWS S3, or Heroku) allows attackers to claim them and serve malicious content under the company's name.
- Asset Inventory: Webmasters and IT admins use this tool to keep track of their digital footprint and ensure no rogue environments are left online.