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How to Install and Use OpenAI Codex CLI: A Step-by-Step Guide

Author AvatarAdvant
April 20, 2025
OpenAI Codex CLI Installation Guide

The OpenAI Codex CLI has become an essential tool for modern developers, as highlighted in our analysis of top AI trends in 2025. This step-by-step guide will walk you through the installation process and show you how to make the most of this powerful AI-powered coding assistant. For a comprehensive overview of Codex CLI's capabilities, you can also check out our developer's guide to AI-powered coding with Codex CLI. If you're interested in how AI is transforming the development landscape, our section on AI-driven automation provides valuable insights into the future of development tools.

Why Use This Tool?

Here's what makes it stand out:

  • Saves Time: Speeds up coding by providing assistance.
  • Integrates Easily: Works seamlessly with your existing tools.
  • Versatile: Handles both small fixes and large projects.

Before You Start: Get Node.js

You'll need Node.js installed first. It's a runtime that lets you run JavaScript on your computer. Here's how to set it up:

  • Download It: Visit the Node.js website and select the version for your operating system (Windows, macOS, or Linux).
  • Install It: Run the downloaded file and follow the installation instructions.
  • Verify It: Open your command line—Terminal on macOS/Linux or Command Prompt on Windows—and type:
node --version

You should see a version number like v18.17.0. If not, reinstall and try again.

Note: Node.js is essential for the Codex CLI, so don't skip this step!

Step 1: Install the Tool

Once Node.js is ready, install the Codex CLI by entering this command in your command line:

npm install -g @openai/codex

This installs the tool globally, so you can use it from anywhere on your computer.

Troubleshooting:

  • Ensure you have permission to install (on macOS/Linux, try adding sudo before the command).
  • Confirm your internet connection is active.
  • New to npm? Check out the npm documentation for more details.

Step 2: Add Your OpenAI Key

The tool requires an API key to connect to OpenAI's services. Here's how to set it up:

  • Sign In: Go to platform.openai.com and log in or create an account.
  • Generate a Key: Navigate to the "API Keys" section, click "Create New Secret Key," name it (e.g., "Codex Key"), enable all permissions, and click "Create Secret."
  • Store It Safely: Copy the key to a secure location—it's only shown once.

Set It Up: Add the key to your system with the appropriate command for your operating system:

For macOS/Linux:

export OPENAI_API_KEY='your-key-here'

For Windows Command Prompt:

set OPENAI_API_KEY='your-key-here'

For Windows PowerShell:

$env:OPENAI_API_KEY='your-key-here'

Try It: Make a To-Do App

Let's create a simple to-do app:

Create a React web app with Shad CN that is a to-do app with persistence

If Something Goes Wrong

Common issues and fixes:

  • Installation Fails: Verify permissions and internet connectivity.
  • Key Issues: Double-check the key and account status.
  • Tool Not Found: Reinstall or review your setup.
  • Odd Output: Rephrase your command.

Easy Tips

  • Review Output: Always check the generated code.
  • Leverage Git: Protect your work with version control.
  • Start Small: Test with simple tasks first.
  • Secure Your Key: Keep it confidential.

Wrap-Up

The OpenAI Codex CLI is a powerful way to integrate AI into your coding workflow. This guide walked you through installation and building a basic app. Now, experiment with it on your projects to streamline your coding!

Need assistance with an AI project? Explore our AI/ML Research & Development services to see how we tackle real-world challenges with AI. For more insights into AI development tools and trends, check out our analysis of why Codex CLI matters in modern development workflows.

OpenAI's also sweetening the deal with a $1 million fund, offering $25,000 API credit grants for open-source projects using Codex CLI. To learn more about how Codex CLI is transforming the development landscape, read our in-depth exploration of OpenAI Codex CLI. Interested? Apply via OpenAI's funding form, they're reviewing applications regularly.