Artificial Intelligence (AI), AI for Developers, AI Tools & Technologies

Step-by-Step Installation, Authentication, and Usage Guide for Anthropic’s Claude Code in 2025: 🚀 Complete Setup Guide for Claude Code (2025 Edition)

by Kinshuk Dutta
This entry is part 2 of 2 in the series AI Tool Series

AI Tool Series

Claude Code is a powerful, terminal-based AI tool from Anthropic that brings agentic workflows and code generation directly to your CLI. If you’re looking to integrate AI seamlessly into your development flow—Claude Code is your new best friend.

💡 This guide walks you through installing, configuring, and using Claude Code from scratch. It also includes solutions for common issues.

🧰 Prerequisites

Before getting started, ensure you have the following:

  • A terminal or command line interface (macOS, Linux, or Windows with WSL)
  • Node.js version ≥ 18 (preferably installed via nvm)
  • npm package manager
  • Access to console.anthropic.com

⚙️ Step-by-Step Installation

1️⃣ Check Your Node.js Version

bash
node --version

If it’s below 18, upgrade using nvm.

2️⃣ Install Node.js v18+ Using NVM

bash
# Install Node.js 18
nvm install 18
nvm use 18

# Or use the latest LTS version
nvm install –lts
nvm use –lts

# Confirm version
node –version

3️⃣ Install Claude Code Globally

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

4️⃣ Verify Installation

bash
claude --version

You should see:
1.0.9 (Claude Code) or similar.

🔐 Authenticate with Anthropic

5️⃣ Login via CLI

bash
claude login

You’ll be prompted to enter your Anthropic API key.

6️⃣ Get Your Anthropic API Key

If you don’t have an API key:

  1. Go to console.anthropic.com
  2. Sign in or create an account
  3. Navigate to API Keys
  4. Click “Create Key”
  5. Copy the key (starts with sk-ant-)
  6. Paste it in when prompted by claude login

🧪 Test Claude Code with a Prompt

bash
claude -p "make a hello.py script that prints 'Hello, world!'"

If everything is set up correctly, Claude will output the Python script within seconds.

🔁 Alternative: Set API Key as Environment Variable

If you prefer not to use claude login, set your API key manually:

bash
# For current session
export ANTHROPIC_API_KEY=sk-ant-yourkey

# Make it persistent
echo ‘export ANTHROPIC_API_KEY=sk-ant-yourkey’ >> ~/.zshrc
source ~/.zshrc

🛠️ Common Issues and Fixes

⚠️ Issue 💡 Cause 🛠️ Solution
Unsupported engine warning Node.js version is too old Upgrade Node.js to v18+ via NVM
ReadableStream is not defined Missing Web Streams support Upgrade Node.js and reinstall Claude Code
Invalid API key Wrong or expired API key Re-authenticate using claude login

✅ Final Check

Try out another prompt to confirm everything is working:

bash
claude -p "generate a shell script to compress all .log files into archive.tar.gz"

🎉 You’re now ready to build, automate, and accelerate your development with Claude Code.

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Kinshuk Dutta
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