Getting Started with Claude Code

Claude Code is an agentic coding assistant that operates directly in your terminal. It can read and edit files, run commands, search your codebase, and interact with Git and GitHub -- all through natural language. This guide walks you through installation, authentication, and your first productive session.

Prerequisites

• Node.js 18+: Claude Code requires Node.js version 18 or later. Check with node --version.
• An Anthropic account: You need an active Anthropic account with API access or a Claude Pro/Team subscription.
• A terminal: Works in any Unix-like shell (macOS Terminal, Linux shell, WSL on Windows, or Git Bash).

Installation

Install Claude Code globally via npm:

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

To verify the installation:

claude --version

Updating

To update to the latest version:

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

Authentication

Run claude for the first time and follow the interactive login flow:

claude

You will be prompted to authenticate through your browser. Once completed, your session credentials are stored locally and persist across sessions.

API Key Authentication

Alternatively, set the ANTHROPIC_API_KEY environment variable:

export ANTHROPIC_API_KEY="sk-ant-..."
claude

First Run

Navigate to your project directory and start Claude Code:

cd your-project
claude

Claude will automatically detect your project structure. Try some basic commands:

• "What does this project do?" -- Claude reads your files and gives a summary.
• "Find all TODO comments" -- Searches the codebase.
• "Run the tests" -- Executes your test suite.
• "Fix the bug in auth.js where the token isn't refreshed" -- Reads, edits, and verifies the fix.

Basic CLI Usage

Interactive Mode (default)

claude                    # Start an interactive session

One-shot Mode

claude -p "explain src/index.ts"         # Print answer and exit
claude -p "add error handling to api.js"  # Make a change and exit

Piping Input

cat error.log | claude -p "explain this error"
git diff | claude -p "review these changes"

Resuming Conversations

claude --resume            # Resume the most recent conversation
claude --continue          # Continue the last conversation with a new prompt

Common Flags

For more CLI options and shortcuts, see Tips and Tricks.

Generate a CLAUDE.md (Fast Path)

The fastest way to get productive is to generate a CLAUDE.md file for your project. You have two options:

Option A: Interactive script — answers 7 questions, outputs a ready-to-use file:

bash tools/generate-claude-md.sh

Option B: Let Claude do it — paste the Quickstart Prompt into a Claude session and it auto-generates one by reading your project files.

Either way, you go from zero to a working CLAUDE.md in under 60 seconds. See the CLAUDE.md Guide for how to refine it further.

Tips for Your First Session

• Start with exploration: Ask Claude to summarize your project or explain a module before making changes.
• Be specific: Instead of "fix the bug", say "fix the null pointer in processOrder when the cart is empty".
• Review changes: Claude shows you diffs before applying them. Take a moment to review.
• Use plan mode for big tasks: Prefix complex requests with "plan:" or use --plan to have Claude outline an approach before executing.

See Also

Now that you are up and running, explore these guides to deepen your usage:

• CLAUDE.md Guide -- Give Claude persistent context about your project
• Prompt Tips -- Write more effective instructions
• Workflow Patterns -- Common development workflows
• Permission Modes -- Control what Claude can do