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Prerequisites

  • Node.js 18 or higher. Check your version with node --version. Download Node.js if needed.
  • A Claude account at claude.ai, or an Anthropic API key.

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Install and authenticate

1

Install globally via npm

npm install -g @anthropic-ai/claude-code
Verify the installation:
claude --version
2

Authenticate

Run claude from any directory. On first launch, Claude Code detects that no credentials are configured and prompts you to log in.
claude
OAuth via claude.ai (recommended): Follow the URL printed in the terminal to complete the OAuth flow in your browser. Your subscription entitles you to use Claude Code without managing API keys.API key: If you prefer to use an API key directly, set the ANTHROPIC_API_KEY environment variable before running claude:
export ANTHROPIC_API_KEY=sk-ant-...
claude
If both an OAuth session and ANTHROPIC_API_KEY are present, Claude Code uses the API key and skips the OAuth flow.
3

Navigate to your project

Claude Code works best when launched from your project root so it can read the files it needs.
cd my-project
claude
4

Ask Claude something

Once the interactive session opens, type a prompt and press Enter:
> explain what this codebase does
Claude reads relevant files and replies in the terminal. You can continue the conversation, ask for edits, run commands, and more — all in the same session.

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First non-interactive call

Use the -p (or --print) flag to run a single prompt and print the result to stdout. This is useful for scripting or quick one-off queries: 
claude -p "what files are in this directory?"
Output is written to stdout, making it easy to pipe into other tools: 
claude -p "list all TODO comments in the codebase" > todos.txt

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Tips for effective use

Start sessions from your project root. Claude Code uses your working directory as the base for all file operations.
  • Be specific about scope. Tell Claude which files or directories are relevant if the codebase is large.
  • Ask for plans before big changes. Prompt Claude to outline what it intends to do before making edits across many files.
  • Use non-interactive mode for automation. The -p flag makes it straightforward to integrate Claude into shell scripts, Makefiles, or CI workflows.
  • Resume sessions. Use claude --resume to continue a previous conversation rather than starting over.

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Next steps

Installation

Full installation options including alternative package managers, Bedrock, and Vertex AI.

Interactive mode

Learn the interactive REPL in depth.