Subfinder

What it does

Subfinder enumerates subdomains using passive online sources, returning results fast without sending traffic to the target. A staple first step in external reconnaissance.

Common use cases

• •Fast passive subdomain discovery during the reconnaissance phase of a pentest.
• •Enumerate subdomains for a bug bounty target without sending traffic to origin servers.
• •Feed discovered subdomains into other tools like dnsx and httpx for live host filtering.

Key features

• •Entirely passive enumeration — no direct traffic to the target.
• •Integrates with 30+ public sources including CertSpotter, AlienVault, and SecurityTrails.
• •Designed for easy piping into other ProjectDiscovery tools.
• •Supports wildcard filtering and recursive enumeration.

Source