How to Use Claude Code: The Complete Guide to AI-Powered Coding in Your Terminal

What is Claude Code?

Claude Code is Anthropic’s AI coding agent that lives in your terminal. It’s not a chatbot with a code plugin — it’s a full autonomous agent that can read your entire codebase, plan multi-file changes, write code, run tests, and commit to git.

If you’ve used Claude the chatbot, think of Claude Code as Claude with hands. Instead of copying code from a chat window, Claude Code edits your files directly.

Why Use Claude Code?

Here’s what makes it different from pasting code into a chat window:

• Full project context — It reads your entire codebase, not just the file you paste
• Multi-file changes — It can refactor across dozens of files in one go
• Runs your tools — It executes tests, linters, and build commands to verify its work
• Git integration — It creates commits with meaningful messages
• Plan-then-execute — It shows you a plan before making changes, so you stay in control

Installation

Prerequisites

You need Node.js 18 or later. Check your version:

node --version

Install

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

First Run

Navigate to any project and run:

cd your-project
claude

The first time, it guides you through authentication. You can use an Anthropic API key or sign in with your Claude account.

Basic Usage

Ask Questions About Your Code

> explain how the authentication flow works in this project

Claude reads the relevant files and gives you a clear explanation — like pair programming with someone who’s already read every file.

Make Changes

> add input validation to the signup form - email format, password strength, and matching password confirmation

Claude plans the changes, tells you which files it will modify, and shows diffs before applying. You approve each step.

Fix Bugs

> the checkout page crashes when the cart is empty - find and fix the bug

Claude searches for the issue, identifies the root cause, and proposes a fix.

Run Commands

> run the test suite and fix any failing tests

Claude executes your tests, reads the error output, and fixes the issues.

Intermediate Techniques

Use Plan Mode

For complex tasks, ask Claude to plan first:

> /plan refactor the API routes from Express to Hono

Claude analyses the codebase, creates a detailed migration plan, and only starts coding after you approve. This is essential for large changes — you don’t want the AI going off on its own for 20 minutes without alignment.

Multi-Turn Conversations

Claude Code remembers context within a session. You can build on previous work:

> add a dark mode toggle
> now persist the preference to localStorage
> also respect the system preference on first load

Each message builds on the last, just like working with a human developer.

CLAUDE.md Files

Create a CLAUDE.md file in your project root to give Claude persistent instructions:

# Project Instructions

## Tech Stack
- React 19, TypeScript, Tailwind CSS v4
- Vitest for testing
- pnpm as package manager

## Conventions
- Use functional components with hooks
- camelCase for variables, PascalCase for components
- Always add TypeScript types, no `any`

Claude reads this file automatically and follows your conventions. Think of it as a system prompt for your entire project.

Advanced Workflows

Autonomous Mode

For routine tasks, let Claude work without step-by-step approval. Use the --allowedTools flag or configure permissions in your settings.

Hooks

Hooks let you run custom scripts before or after Claude takes certain actions. For example, auto-format code after every edit, or run linting before every commit.

MCP Servers

Claude Code can connect to external tools through the Model Context Protocol (MCP). This lets it access databases, APIs, design tools, and other systems your project depends on.

Sub-Agents

For complex tasks, Claude Code can spawn sub-agents that work on different parts of the problem in parallel. This is how it handles large refactors efficiently.

Claude Code vs Other AI Coding Tools

For a deeper comparison, see our Claude Code vs Cursor breakdown.

Tips for Getting Better Results

1. Be specific — “Add error handling to the payment flow” beats “improve the code”
2. Give context — Mention the tech stack, constraints, and what you’ve already tried
3. Use plan mode for big changes — Don’t let it start a 500-line refactor without alignment
4. Review diffs carefully — Claude is good but not perfect. Read what it writes.
5. Iterate — The first pass is a draft. Follow up with refinements.
6. Write a CLAUDE.md — Project-specific instructions save time on every interaction

Common Issues

”Command not found” after installing

Make sure your npm global bin directory is in your PATH. Run npm config get prefix and add /bin to your shell profile.

Slow responses

Claude Code reads your project files for context. Very large repositories may be slower. Use .claudeignore to exclude directories that aren’t relevant (like node_modules, dist, or large data files).

Token usage seems high

Large projects consume more tokens because Claude reads more context. Use /compact to compress conversation history, and keep your CLAUDE.md focused to reduce overhead.

What’s Next?

• Prompt Engineering Fundamentals — Write better instructions for Claude Code
• Automate Your Workflows with AI — Use Claude Code to build automation pipelines
• Building AI Agents from Scratch — Understand how Claude Code works under the hood
• Understanding Code Without Being a Coder — Build the code literacy to work effectively with Claude Code