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Subfinder

Recon / OSINT · Beginner

Passive subdomain discovery from public sources.

Knowledge reference only. Prefer in-browser Labs first. Use this tool only on systems you own or have written authorization to test.

What to learn

  • Provider API keys
  • Output formats

Legitimate use

Subfinder is used legitimately by security teams for authorized testing, defense validation and education.

Official docs →

Example commands (lab VMs only)

  • subfinder -d example.com
    Passive subdomain discovery