# Subfinder Fast Passive Subdomain Enumeration Tool

> Subfinder is a passive subdomain discovery tool by ProjectDiscovery that finds valid subdomains for websites using curated online sources. Optimized for speed and stealth, it integrates cleanly into security reconnaissance pipelines via stdin/stdout support.

- Skill: `agentskillexchange/subfinder-fast-passive-subdomain-enumeration-tool` (Agent Skill)
- Install (CLI): `npx skillmds@latest add agentskillexchange/subfinder-fast-passive-subdomain-enumeration-tool`
- Raw SKILL.md: https://api.skillmd.com/api/skills/agentskillexchange/subfinder-fast-passive-subdomain-enumeration-tool/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Product & Planning
- Author: agentskillexchange (https://skillmd.com/u/agentskillexchange)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/agentskillexchange/subfinder-fast-passive-subdomain-enumeration-tool

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# Subfinder Fast Passive Subdomain Enumeration Tool

Subfinder is a passive subdomain discovery tool by ProjectDiscovery that finds valid subdomains for websites using curated online sources. Optimized for speed and stealth, it integrates cleanly into security reconnaissance pipelines via stdin/stdout support.

## Prerequisites

Go 1.21+

## Installation

No source-backed install or usage instructions could be extracted automatically. Review the upstream project before running this skill in a sensitive workflow.

- Source: https://github.com/projectdiscovery/subfinder

## Documentation

- https://docs.projectdiscovery.io/tools/subfinder/overview

## Source

- [Agent Skill Exchange](https://agentskillexchange.com/skills/subfinder-passive-subdomain-enumeration/)