Cursor Rules: Customizing Your AI Pair Programmer

Does your AI assistant keep using const when you prefer let? (Just kidding, nobody prefers let). But seriously, does it keep ignoring your project's folder structure or inciting "useEffect" chaos?

Enter Cursor Rules.

What is .cursorrules?

It's a file you drop in the root of your project. Think of it as the "Constitution" for your AI agent. Every time you start a chat or generate code, Cursor reads this file first.

Best Practices for a Vibe-Approved Rule File

1. Be Specific, Not Polite

Don't say: "Please try to use Tailwind." Do say: "ALWAYS use Tailwind utility classes. NEVER create custom CSS files."

2. The "Gold Standard" Technique

Instead of writing 10 paragraphs explaining your architecture, point to a file that does it right.

# Style Guide
Refer to @components/Button.tsx for the preferred structure of a React component.
Refer to @lib/utils.ts for how to handle helper functions.

3. Tech Stack Definition

Explicitly state your stack so the AI doesn't guess.

# Tech Stack
- Framework: Next.js 15 (App Router)
- Styling: Tailwind CSS
- Database: Supabase
- Auth: Clerk

Example .cursorrules for 2025

Here is a snippet you can copy-paste to get started:

You are an expert full-stack developer.
 
1.  **Architecture**: Use Server Actions for all data mutations. Do not use API routes unless necessary for external webhooks.
2.  **Styling**: Use Shadcn UI components where possible. Default to "Radix Colors".
3.  **Types**: Strict TypeScript. No "any".
4.  **Testing**: Write Vitest tests for all utility functions.

Conclusion

A well-crafted .cursorrules file turns a generic AI into a senior engineer who has been on your team for 5 years. It is the highest ROI text file in your repo.

Want to find pre-made rules? Check out the Directory for community templates.