Getting Started with Claude Code

Claude Code is Anthropic's AI coding agent. It runs in your terminal, reads your entire codebase, edits files, runs commands, manages git, and builds features from plain English descriptions. This guide walks you through installation, your first session, project configuration, and the workflows that make Claude Code worth using every day.

Prerequisites

Before you start, make sure you have:

• A terminal (macOS Terminal, iTerm2, Windows Terminal, or any Linux terminal)
• Git installed and configured
• A Claude subscription (Pro at $20/mo, Max at $100/mo or $200/mo, Teams, or Enterprise) or an Anthropic Console account with API credits

Node.js is not required for the recommended installation method.

Install Claude Code

The recommended way to install Claude Code is the native installer, which handles auto-updates automatically.

macOS and Linux

curl -fsSL https://claude.ai/install.sh | bash

Windows PowerShell

irm https://claude.ai/install.ps1 | iex

Windows CMD

curl -fsSL https://claude.ai/install.cmd -o install.cmd && install.cmd && del install.cmd

Windows users need Git for Windows installed first.

Alternative installation methods

Homebrew (macOS):

brew install --cask claude-code

WinGet (Windows):

winget install Anthropic.ClaudeCode

npm (any platform with Node.js 18+):

npm install -g @anthropic-ai/claude-code

Homebrew, WinGet, and npm installations do not auto-update. You will need to manually upgrade periodically.

Verify the installation

claude --version

You should see a version number printed to your terminal. If not, restart your terminal and try again.

Your first session

Navigate to any project directory and start Claude Code:

cd ~/my-project
claude

On first launch, Claude Code opens a browser window for authentication. Log in with your Claude account and return to the terminal. Your credentials are stored locally - you will not need to log in again.

You will see the Claude Code welcome screen with your session info and recent conversations. The cursor sits at a prompt where you type natural language instructions. No special syntax required.

Ask your first question

Start by understanding what you are working with:

what does this project do?

Claude reads your project files and returns a summary of the codebase, its structure, and the technologies used. You can follow up with more specific questions:

explain the folder structure

where is the main entry point?

what dependencies does this project use?

Claude Code reads files on demand as it needs them. You do not need to manually point it at specific files.

Make your first code change

Tell Claude what you want in plain English:

add input validation to the signup form

Claude Code will:

1. Find the relevant files in your codebase
2. Show you the proposed changes as a diff
3. Wait for your approval before writing anything
4. Apply the changes once you confirm

You always see exactly what Claude plans to change before it touches a file. Press y to accept or n to reject each change.

Set up CLAUDE.md

CLAUDE.md is a markdown file in your project root that tells Claude Code about your project. It loads automatically at the start of every session. Think of it as a README written specifically for your AI coding partner.

Generate one automatically

The fastest way to create a CLAUDE.md is to let Claude do it:

/init

Claude analyzes your codebase and generates a CLAUDE.md with build commands, test instructions, directory structure, and coding conventions it discovers. Review the output and refine it with anything Claude would not know on its own.

Write one manually

Create a CLAUDE.md file in your project root:

# My Project

## Stack
Next.js 16 + Convex + Clerk + Tailwind CSS v4

## Key Directories
- src/app/ -- Pages and layouts (App Router)
- src/components/ -- React components
- convex/ -- Backend functions and schema
- src/lib/ -- Shared utilities

## Commands
- npm run dev -- Start dev server on port 3000
- npx convex dev -- Start Convex backend
- npm test -- Run test suite
- npm run lint -- Run ESLint

## Conventions
- Use TypeScript strict mode
- Prefer server components by default
- Use 2-space indentation
- Write tests for all new utilities

What to include

A good CLAUDE.md covers:

• Stack and architecture. What frameworks, languages, and tools the project uses.
• Directory structure. Where key code lives so Claude finds things faster.
• Build and test commands. The exact commands to build, test, lint, and deploy.
• Coding conventions. Indentation, naming, file organization, import patterns.
• Workflow rules. Things like "always run tests before committing" or "use conventional commits."

Keep it under 200 lines. Concise instructions get followed more reliably than long documents. If you need more detail, split it into files under .claude/rules/ - these load automatically alongside your CLAUDE.md.

CLAUDE.md locations

CLAUDE.md files can live in multiple places, each with a different scope:

Project-level files are great for team standards. Personal files are for your own preferences across all projects.

Essential commands

These are the commands you will use daily:

In-session commands

Once inside a Claude Code session, these slash commands are available:

Press ? in a session to see all keyboard shortcuts. Use Tab for command completion and the up arrow for command history.

Key features

File editing

Claude Code reads and edits files directly. It shows you a diff of every proposed change and waits for approval before writing. You can ask it to:

refactor the auth middleware to use async/await

add error handling to all API routes

rename the User model to Account across the entire codebase

Claude handles multi-file changes in a single operation. It understands imports, references, and dependencies across your project.

Test running

Claude Code runs your test suite and interprets the results:

run the tests and fix any failures

write unit tests for the payment module, then run them

add integration tests for the user API endpoints

It reads test output, identifies failures, fixes the code, and re-runs tests until they pass. This loop is one of the most powerful workflows in Claude Code.

Git integration

Git operations become conversational:

what files have I changed?

commit my changes with a descriptive message

create a branch called feature/user-profiles

create a pull request for this feature

help me resolve these merge conflicts

The claude commit shortcut is particularly useful. Run it from the command line and Claude stages your changes, writes a commit message based on the actual diff, and commits - all in one step.

Plan mode

For complex tasks, use Plan mode to get Claude to analyze and plan before making changes:

use plan mode: refactor the database layer to support multi-tenancy

In Plan mode, Claude reads your code and produces a detailed plan without editing anything. Once you review and approve the plan, switch to normal mode to execute it. This is useful for large refactors, architectural changes, or any task where you want to think before acting.

Piping and scripting

Claude Code follows Unix conventions. You can pipe data in and out:

# Analyze log output
tail -200 app.log | claude -p "summarize any errors in this log"

# Review changed files
git diff main --name-only | claude -p "review these files for security issues"

# Generate from a template
cat template.md | claude -p "fill in this template for our new API endpoint"

The -p flag runs Claude in non-interactive mode, making it composable with other CLI tools.

Common workflows

Explore a new codebase

give me an overview of this codebase

explain the main architecture patterns used here

trace the request flow from the API endpoint to the database

Fix a bug

I'm getting "Cannot read property of undefined" when users submit the form. Fix it.

Claude traces the error through your code, identifies the root cause, and implements the fix. Give it the exact error message and any steps to reproduce.

Add a feature

add a dark mode toggle to the settings page. Use the existing theme system.

Claude plans the approach, writes the code across multiple files, and verifies it works with your existing patterns.

Write and run tests

write tests for the payment processing module, run them, and fix any failures

This single prompt triggers Claude to write test files, execute your test runner, read the output, fix any failures, and repeat until everything passes.

Refactor

refactor the user service from callbacks to async/await

split this 500-line component into smaller, reusable components

Create a pull request

create a PR with a summary of all the changes we made in this session

Claude stages changes, creates a branch, writes a PR title and description, and opens the pull request.

Tips for better results

Be specific. "Fix the login bug where users see a blank screen after entering wrong credentials" works much better than "fix the login bug."

Give context. If you know where the problem is, say so. "The issue is in src/auth/login.ts around line 45" saves Claude from searching the entire codebase.

Break big tasks into steps. Instead of "build a complete user management system," try:

1. create a database schema for user profiles
2. add API endpoints for CRUD operations on profiles
3. build a settings page that uses those endpoints

Let Claude explore first. Before asking for changes, let Claude understand the code:

analyze the payment module before we make changes

Use auto memory. Claude Code automatically remembers things across sessions - build commands, debugging insights, your preferences. You can also tell it explicitly: "remember that the tests require a local Redis instance."

Keep CLAUDE.md current. When your project conventions change, update CLAUDE.md. Outdated instructions cause confusion.

Where to use Claude Code

Claude Code is available across multiple surfaces, all sharing the same configuration:

Your CLAUDE.md files, settings, and MCP servers work across all of them.

Next steps

Once you are comfortable with the basics:

• CLAUDE.md deep dive - Advanced configuration including custom skills, hooks, and MCP servers
• MCP Servers - Connect external tools to Claude Code
• Official docs - Full reference documentation from Anthropic
• Best practices - Patterns for getting the most out of Claude Code
• Common workflows - Detailed guides for specific development tasks

Claude Code gets more useful the more you invest in CLAUDE.md and your project configuration. Start simple, iterate as you learn what works, and let auto memory handle the rest.