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:

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

To verify the installation:

bash claude --version

Updating¶

To update to the latest version:

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

Authentication¶

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

bash 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:

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

First Run¶

Navigate to your project directory and start Claude Code:

bash 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)¶

bash claude # Start an interactive session

One-shot Mode¶

bash 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¶

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

Resuming Conversations¶

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

Common Flags¶

Flag	Description
`-p "prompt"`	Run in non-interactive (print) mode
`--resume`	Resume the last conversation
`--continue`	Continue the last conversation
`--model`	Specify a model (e.g., `claude-sonnet-4-6`)
`--allowedTools`	Restrict which tools Claude can use
`--verbose`	Show detailed tool usage output

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 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.

What's Next¶

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