Free Subdomain Finder
Discover all subdomains of any domain using Certificate Transparency logs. Find shadow IT, forgotten assets, and your full attack surface.
Why subdomain discovery matters for security
Every subdomain is a potential entry point for attackers. Forgotten staging environments, abandoned test servers, and misconfigured APIs are routinely exploited because nobody was watching them. This tool uses Certificate Transparency logs — a public record of every SSL certificate ever issued — to discover all subdomains associated with your domain.
Continuous subdomain monitoring is a core part of Attack Surface Management (ASM). Xentinel monitors your subdomains 24/7 and alerts you when new ones appear.