What is a subdomain finder?

A subdomain finder is a tool that discovers all subdomains of a root domain using Certificate Transparency logs and other public sources.

How do I find all subdomains of a website?

Enter a domain into the Subdomain Finder and click Find Subdomains. It queries Certificate Transparency logs and returns all subdomains that have had public SSL certificates.

Is the Subdomain Finder free?

Yes, 100% free. No signup, no API key, no scan limits.

How accurate is the tool?

Certificate Transparency logs capture 85-95% of active subdomains because virtually all public services now use SSL certificates.

Free Subdomain Finder

Discover all subdomains of any domain using Certificate Transparency logs. Find admin panels, staging servers, API endpoints, and hidden subdomains instantly and for free.

How to find subdomains (step-by-step)

Enter a root domain (e.g. github.com)
Click "Find Subdomains"
Review the results table — subdomain, first-seen date, last-seen date, certificate count
Filter, copy all, or download as CSV

Who uses a subdomain finder?

Security researchers & bug bounty hunters — map the attack surface of authorized targets
Penetration testers — scope engagements with passive reconnaissance
DevOps & SRE teams — inventory subdomains before DNS migrations
Marketing teams — discover what competitors are building
Blue teams — monitor your own CT footprint for shadow IT

Frequently asked questions

Is it free?

Yes, completely free with no signup, no API key, no scan limits.

How accurate is it?

Certificate Transparency logs capture 85-95% of active subdomains. Only subdomains without SSL certificates won't appear.

Is it legal?

Yes, CT logs are public data. However, using discovered subdomains for unauthorized security testing is illegal — only test domains you own or have permission to test.

Does it do DNS brute-forcing?

No. This is passive reconnaissance — no traffic is sent to the target domain.

Related tools

Website Traffic Checker — analyze any domain's visits, bounce rate, and rankings
Domain Comparison — compare up to 5 websites side-by-side
Trending Domains — most analyzed sites this week

Try the free subdomain finder for github.com, google.com, or any domain.