Overview

Subfinder is a fast, open-source passive subdomain enumeration tool developed by ProjectDiscovery. It discovers subdomains by collecting information from multiple public OSINT sources without directly interacting with the target.

It is widely used by penetration testers, bug bounty hunters, and red teams during the reconnaissance phase to identify an organization's exposed assets.

Purpose

The primary purpose of Subfinder is to discover subdomains associated with a target domain using passive intelligence sources.

Example:

Target:
example.com

Possible Results:
mail.example.com
vpn.example.com
api.example.com
dev.example.com
staging.example.com

Key Features

• Passive Subdomain Enumeration
• Fast and Lightweight
• Open Source
• Supports Multiple Data Sources
• API Integration
• Recursive Enumeration
• Output Filtering
• JSON Output Support
• Wildcard Elimination
• Easy Automation