If you use Claude Code, you already know it's one of the best AI coding tools out there. But most people don't know about its most powerful feature: skill files.
A skill file is a .md file you drop into ~/.claude/skills/. Claude reads it automatically and follows those instructions whenever relevant. It's like giving Claude a cheat sheet written by a senior engineer.
The problem? Writing good skill files takes time. A vague prompt gives you vague code. A detailed skill file with real commands, working examples, and specific pitfalls gives you production-ready output.
So I built CLSkills — a free, searchable library of 789 skill files across 71 categories.
How it works
1. Create the skills directory (one time)
mkdir -p ~/.claude/skills
2. Download any skill
curl -o ~/.claude/skills/docker-compose.md \
https://clskills.in/skills/docker/docker-compose.md
3. Use Claude Code normally — it reads the skill automatically
claude "set up a docker compose for my Node app with PostgreSQL and Redis"
That's it. No config, no plugins, no setup.
What's inside each skill
Every skill follows the same structure:
Expert role — Claude adopts a specific persona. Not "helpful assistant" but "senior DevOps engineer specializing in container orchestration."
What to check first — prerequisites before starting. Does the project have a Dockerfile? Is Docker installed? What version?
Step-by-step instructions — numbered steps with real commands. Not "set up the database" but "run docker compose up -d postgres and verify with docker compose ps."
Working code — 25-40 lines of copy-paste ready code. Not pseudocode, not skeleton code. Real, working implementations.
Pitfalls — things that actually go wrong with that specific technology. Not generic advice like "handle errors" but "PostgreSQL containers take 5-10 seconds to initialize — add a health check with pg_isready before starting dependent services."
Example: Two Factor Auth skill
Here's what a real skill looks like:
You are a security engineer implementing two-factor authentication.
The user wants to add 2FA/MFA to an existing auth flow using TOTP
and backup codes.
What to check first
- Verify speakeasy or otplib is installed: npm list speakeasy
- Confirm database has twoFactorSecret, twoFactorEnabled, backupCodes columns
- Check JWT secret or session store is configured
Steps
- Install packages: npm install speakeasy qrcode
- Create 2FA setup endpoint using speakeasy.generateSecret() and return QR code via qrcode.toDataURL()
- Create verification endpoint with speakeasy.totp.verify()
- Generate 8-10 backup codes, store them hashed in the database
- Add 2FA check middleware on protected routes
- Create backup code redemption endpoint
- Implement "remember this device" with a 30-day cookie
- Add disable 2FA endpoint requiring password + valid TOTP token
Pitfalls
- Never log TOTP secrets — they're equivalent to passwords
- Always hash backup codes with bcrypt before storing
- Use 30-second window for TOTP verification, not 60
- Rate limit verification attempts to prevent brute force When Claude reads this, it doesn't just "try its best." It follows these exact steps, uses the right packages, and avoids the specific mistakes that would bite you in production.
What categories are covered
71 categories across every area of development:
Frontend: React, Vue, Angular, Svelte, Next.js, Tailwind
Backend: Node.js, Python, Go, Rust, Java, GraphQL, REST, gRPC
DevOps: Docker, Kubernetes, CI/CD, Terraform, Ansible
Cloud: AWS, GCP, Azure, Serverless, Edge Functions
Databases: PostgreSQL, MongoDB, Redis, Elasticsearch, Prisma
Testing: Unit, Integration, E2E, React Testing Library, Playwright
Security: Auth, OAuth, JWT, CORS, Secrets Management
And more: AI/ML, Mobile, Desktop, CLI Tools, Payments, Search, Monitoring...
Why this matters
I've been using Claude Code daily for months. The difference between Claude with and without skill files is massive.
Without skills: "Here's a basic Docker setup..." followed by a generic Dockerfile that works but misses health checks, multi-stage builds, non-root users, and layer caching.
With skills: Claude produces the exact same output a senior DevOps engineer would write — because it's following instructions written by one.
The skills essentially encode expert knowledge into a format Claude can follow consistently. You get senior-level output every time, not just when Claude "feels like it."
Try it
Browse all 789 skills at clskills.in
Everything is free, no login required, no paywall. Download individual .md files or grab entire collections as a ZIP.
The project is open source: GitHub
If you have skill ideas or want to contribute, join us at r/ClaudeCodeSkills.
What skills do you use with Claude Code? I'd love to hear what workflows people are building.
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