Essential CLAUDE.md Setup Guide
Learn how to create effective CLAUDE.md files that serve as your primary context mechanism for better AI collaboration.
Essential CLAUDE.md Setup Guide
The CLAUDE.md file is your most important tool for establishing effective context with Claude Code. This file acts as persistent instructions that Claude references in every session, making it crucial to get right from the start.
What is CLAUDE.md?
CLAUDE.md is a markdown file that lives in your project root (and optionally in your global .claude directory) that provides Claude Code with essential context about your project. Think of it as a briefing document that ensures consistent, informed assistance across all sessions.
Essential Components
1. Development Commands
Always include your most common commands:
markdownnpm run devDevelopment Commands
- - Start development servernpm run build
- - Build production application npm run test
- - Run test suitenpm run lint
- - Run ESLintnpm run typecheck
- - Run TypeScript compiler
2. Code Style Guidelines
Define your project's conventions clearly:
markdown
Code Style
- Use TypeScript strict mode
- Prefer functional components with hooks
- Use descriptive variable names
- Follow existing import patterns
- Add JSDoc comments for complex functions
3. Testing Approach
Specify how testing should be handled:
Testing
- Use Jest for unit tests
- Write tests alongside implementation files
- Aim for behavioral testing over implementation testing
- Mock external dependencies, not internal modules
4. Project Structure
Help Claude understand your architecture:
Architecture
- src/app/
- Next.js app router pages
- src/components/ - Shared React components
- src/lib/ - Utility functions and data processing
- src/types/ - TypeScript type definitions
Best Practices
Keep It Concise
Your CLAUDE.md should be scannable. Aim for essential information only. If Claude needs to read a novel to understand your project, it's too long.
Make It Human-Readable
Remember that team members will read this file too. Write it as documentation that helps both AI and humans understand your project quickly.
Update Regularly
As your project evolves, update your CLAUDE.md. Outdated information is worse than no information.
Use Specific Examples
Instead of "follow React best practices," specify:
markdownuseStateComponent Patterns
- Use and useEffect for local state
- Prefer controlled components for forms
- Extract custom hooks for shared logic
Common Mistakes to Avoid
Over-Specification
Don't include every possible detail. Focus on what's genuinely different or important about your project.
Outdated Information
Regularly review and update your CLAUDE.md when you change tools, patterns, or conventions.
Generic Advice
Avoid copying generic best practices. Include only what's specific to your project's needs and conventions.
Global vs. Project CLAUDE.md
- Global (~/.claude/CLAUDE.md): Personal preferences, general setup instructions
- Project (project root): Project-specific conventions, architecture, commands
The project-level file takes precedence and should be committed to version control for team consistency.
Real-World Example
Here's a minimal but effective CLAUDE.md:
markdownProject Context
Commands
- npm run dev
- Development server (http://localhost:3000)
- npm run build && npm run start - Production build and serve
- npm run test - Jest test suite
- npm run lint - ESLint + PrettierCode Style
- TypeScript strict mode enabled
- Use Tailwind for styling (no custom CSS)
- Functional components with hooks
- Co-locate components with their testsTesting
- Jest + React Testing Library
- Test user behavior, not implementation
- Mock API calls using MSWImportant Notes
- All API routes require authentication middleware
- Images must be optimized before committing
- Use @/ imports for src/ directory
Getting Started
1. Create CLAUDE.md in your project root
2. Start with commands and basic structure
3. Add project-specific conventions as they arise
4. Commit to version control for team consistency
5. Review and update regularly
A well-crafted CLAUDE.md transforms Claude from a generic assistant into a knowledgeable team member who understands your project's unique requirements and conventions.