Installation and First Launch - Quickstart

Install Claude Code and launch your first codebase analysis in under 5 minutes. This quickstart guide covers npm installation, OAuth authentication, and immediate hands-on use of the tool - step by step, no detours.

The native and npm installation of Claude Code is the fastest way to get started with this command-line development assistant created by Anthropic. Claude Code installs with a single command and supports over 30 programming languages. Claude Code reduces time spent on repetitive development tasks by 40%.

What are the system prerequisites for installing Claude Code?

Before starting the installation, verify that your machine has the following:

• Node.js 18+ (LTS 22 recommended in 2026) - node -v to check
• Git 2.40+ - required for repository analysis
• A terminal: Terminal.app (macOS), Windows Terminal, or any Linux emulator
• An Anthropic account with a Claude Pro, Team, or Enterprise subscription

If Node.js is not installed, run brew install node on macOS or download the installer from nodejs.org. For a detailed guide on each component, see the complete installation and first launch tutorial which also covers advanced configurations.

Key takeaway: Node.js 18+ and Git 2.40+ are the only two essential prerequisites.

How to install Claude Code via npm in one command?

Open your terminal and run the following command:

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

The installation takes about 45 seconds on a standard connection. The package weighs 85 MB once decompressed.

Verify that the installation worked:

claude --version

You should get a version number like Claude Code v1.0.33 or higher. In practice, 95% of installation errors come from an outdated Node.js version.

If you prefer an isolated installation without polluting your global environment, use npx:

npx @anthropic-ai/claude-code

For specific cases like enterprise proxies, the installation and first launch FAQ addresses the most common issues. You will also find solutions for constrained environments.

Key takeaway: a single command npm install -g @anthropic-ai/claude-code is all you need to install Claude Code globally.

How to resolve authentication and OAuth flow on first launch?

OAuth authentication is the mechanism that links Claude Code to your Anthropic account. Launch Claude Code for the first time:

claude

A link appears in the terminal. Open this link in your browser. You are redirected to the Anthropic login page where you authorize Claude Code to access your account.

the OAuth token is stored locally in ~/.claude/ and renews automatically. In practice, you only need to authenticate once per machine.

If the browser does not open automatically, copy the URL manually. For environments without a graphical interface (servers, Docker containers), use an API key:

export ANTHROPIC_API_KEY="sk-ant-your-key-here"
claude

In case of authentication issues, the permissions and security guide details the available authorization modes and best practices for securing your configuration.

Key takeaway: the OAuth flow happens only once - Claude Code stores and renews the token automatically.

How to understand your codebase with Claude Code in 5 minutes?

Understanding your codebase with Claude in 5 minutes is possible from the very first launch. Navigate to the root of your project and launch Claude Code:

cd /path/to/your-project
claude

Claude Code automatically analyzes the project structure: files, dependencies, configuration. Ask your questions directly in natural language.

Here is how to use the most helpful commands at startup:

> Explain the architecture of this project
> What are the main entry points?
> Summarize the contents of src/index.ts
> Find all API calls in this project

In practice, Claude Code indexes a 50,000-line project in under 10 seconds. It understands relationships between files, imports, and dependencies without any prior configuration.

To go further with exploration, the essential slash commands let you interact more efficiently with the tool. You can also check the first conversation examples to discover concrete use cases.

Key takeaway: run claude at the root of your project and ask your questions - no configuration needed.

Which keyboard shortcuts speed up navigation in Claude Code?

Claude Code keyboard shortcuts let you navigate without leaving the terminal. Here are the most useful combinations to memorize from day one:

Test the /help command immediately to display the full list of available options:

/help

Slash commands are at the core of advanced interaction with Claude Code. Try /init to generate a CLAUDE.md file that will serve as persistent memory for your assistant. To master all shortcuts, the slash commands guide with examples offers step-by-step scenarios.

In practice, the /init command creates a configuration file in 3 seconds that customizes Claude Code's behavior for your project. The CLAUDE.md memory system tutorial explains how to leverage this feature so that Claude remembers your preferences and team conventions.

Key takeaway: /help, Tab, and Ctrl+C are the three shortcuts to know from your very first session.

How to verify that everything works correctly?

After installation, run this complete verification sequence:

claude --version        # Verify installation
claude "Say hello"      # Test API connection
claude "What OS?"       # Validate command execution

If all three commands return a result, your installation is operational. Total verification time does not exceed 30 seconds.

Quick checklist:

1. claude --version displays a version number -> installation OK
2. claude "Say hello" returns a response -> authentication OK
3. claude in a Git repo -> codebase analysis OK

In case of error, the most common causes are: Node.js version below 18, unconfigured proxy, or expired token. The installation cheatsheet gathers all diagnostic commands on a single page.

SFEIR Institute offers a dedicated one-day Claude Code training that lets you master the tool through hands-on labs, from installation to advanced workflows. For those who want to integrate Claude Code into a broader approach, the 2-day AI-Augmented Developer training covers the full range of development assistance tools.

Key takeaway: three commands are enough to validate a complete Claude Code installation.

What are the next steps after installation?

Your Claude Code environment is ready. Here is how to deepen your mastery of the tool:

• Explore your first conversations with Claude Code to learn how to formulate effective requests
• Configure the CLAUDE.md memory system to customize Claude Code for your project
• Discover MCP (Model Context Protocol) to connect Claude Code to external tools like databases or APIs
• Master the essential slash commands to speed up every interaction

In practice, developers who configure CLAUDE.md from day one gain 25% additional productivity according to SFEIR feedback. The one-day AI-Augmented Developer - Advanced training teaches you to leverage advanced patterns like autonomous agents and CI/CD integration.

Key takeaway: configure CLAUDE.md and explore slash commands to get the most out of Claude Code from your very first days.