OpenAI Codex CLI lets developers use an AI coding assistant directly from their computer’s terminal. It can read project files, write code, fix errors, explain existing functions, and help with software development tasks. The installation process is straightforward, but users need a supported environment, Node.js, and access to an OpenAI account.
If you want to get started, this walkthrough covers the requirements, installation steps, account setup, basic commands, and common problems. It is designed for beginners as well as developers who want to add an AI assistant to their existing workflow.
Table of Contents
What Is OpenAI Codex CLI?
Codex CLI is a command-line coding agent developed by OpenAI. Instead of opening a separate application for every coding task, users can interact with Codex through a terminal window.
It can work with files inside a selected project directory and help with tasks such as:
Writing new functions and code snippets.
Finding and fixing programming errors.
Explaining unfamiliar code.
Updating existing project files.
Running development commands.
Reviewing changes and suggesting improvements.
One useful feature is that Codex can understand the context of a project rather than responding only to isolated code snippets. This makes it helpful when working on larger applications.
Requirements Before Installing Codex CLI
Before starting the codex cli install process, check that your computer has the basic tools required to run it.
1. A Supported Operating System
Codex CLI supports macOS, Linux, and Windows environments. Windows users can use Windows Subsystem for Linux (WSL), which provides a Linux environment inside Windows.
2. Node.js and npm
The npm installation method requires Node.js and its package manager, npm. Installing Node.js also provides npm in a standard installation.
You can check whether both tools are available by opening your terminal and running:
node -v
npm -vIf both commands return version numbers, the tools are available. If they are not recognized, install Node.js from its official website before continuing.
3. An OpenAI Account
You will need an OpenAI account to authenticate Codex. The available access and usage limits depend on your account and plan.
Keep your login details secure and avoid sharing authentication information with other people.
How to Install Codex CLI on Different Operating Systems
There are several ways to install Codex CLI. You can use the official standalone installer, npm, or Homebrew. Choose the method that matches your operating system and existing development tools.
Method 1: Install on Windows
Windows users can install Codex directly through PowerShell.
Follow these steps:
Open the Start menu.
Search for PowerShell.
Open a PowerShell window.
Copy and run the following command:
powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"Wait for the installer to finish.
Open a new terminal window and enter:
codex --versionIf a version number appears, the installation is working.
Windows users can also use Windows Subsystem for Linux (WSL) if they prefer working in a Linux environment. Both native Windows and WSL are supported options.
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Method 2: Install on macOS or Linux
The official standalone installer is a convenient option for Mac and Linux users.
Open Terminal and run:
curl -fsSL https://chatgpt.com/codex/install.sh | shThe installer downloads and sets up the appropriate Codex executable for your system.
After installation, check that the command is available:
codex --versionYou can also install Codex through Homebrew on macOS:
brew install --cask codexThis method is useful for developers who already manage their applications through Homebrew.
Method 3: Install Using npm
If Node.js and npm are already installed, you can use npm to install Codex globally.
Open your terminal and enter:
npm install -g @openai/codexThe global installation makes the codex command available from your terminal.
To confirm that everything is ready, run:
codex --versionImportant: Node.js is required for the npm installation method, but it is not necessary when using the standalone installer. This gives users more than one way to set up the tool.
How to Sign In to Codex CLI
Once the installation is complete, the next step is authentication.
Open your terminal and type:
codexThe first time you launch the application, it will display an authentication option.
Choose Sign in with ChatGPT and follow the instructions on the screen. Complete the login process using your OpenAI account.
You can also authenticate using an API key if you prefer that method and have completed the required configuration.
Your available Codex access depends on your ChatGPT plan or API setup. Check the official documentation for current access details.
How to Run Your First Coding Task
After signing in, you can start using Codex inside a project directory.
For example, if your project is stored in a folder called my-website, open that folder in your terminal:
cd my-websiteThen start Codex:
codexOnce the interactive terminal interface opens, enter a simple request, such as:
“Explain the structure of this project and identify its main files.”
Codex will inspect the available project files and provide an explanation.
You can also try practical tasks such as:
Find errors in my JavaScript files.
Explain how the login system works.
Improve the readability of this Python function.
Create a simple contact form.
Review the recent code changes.
Start with smaller requests so you can understand how the tool works before assigning larger development tasks.
Important Safety Tips When Using Codex
Codex can interact with your local project files, so it is important to understand what it is allowed to do.
Before asking it to make major changes, consider these precautions:
Use Git: Create a Git commit before making significant changes. This gives you a recovery point if something goes wrong.
Review code changes: Check the updated files before accepting important modifications.
Protect private information: Avoid exposing passwords, API keys, or confidential project data.
Check terminal commands: Understand commands before allowing them to run, especially those that delete files or change system settings.
Use project instructions: Keep relevant development rules in an
AGENTS.mdfile so Codex can follow your preferred coding practices.
These habits make AI-assisted development easier to manage and reduce the risk of unwanted changes.
Common Codex CLI Installation Problems
Sometimes users encounter errors during setup. Most problems are related to terminal configuration, permissions, or missing dependencies.
The Codex Command Is Not Recognized
If your terminal displays an error saying that codex is not recognized, try opening a new terminal window.
If the problem continues, check whether the installation directory is included in your system’s PATH environment variable.
npm Installation Fails
If npm displays a permission error, check your Node.js and npm configuration. Avoid using administrator privileges unnecessarily, and make sure npm is correctly installed.
You can check the installed versions with:
node -v
npm -vAuthentication Does Not Work
If you cannot sign in, check your internet connection and make sure you are using the correct OpenAI account.
You can also close the terminal and start Codex again to retry authentication.
How to Update Codex CLI
Keeping the application updated helps you access new features and improvements.
For npm installations, run:
npm install -g @openai/codexFor macOS and Linux standalone installations, run the official installer again. Homebrew users can update their installation with:
brew upgrade --cask codexThese methods follow the installation options provided in the official Codex repository.
Final Thoughts
OpenAI Codex makes it easier to work with code directly from a terminal. It can help developers understand existing projects, create new features, identify errors, and improve their development workflow.
The codex cli install process offers different options for Windows, macOS, and Linux users. You can choose the standalone installer, npm, or Homebrew depending on your system.
After setting up the tool and signing in, start with a small coding task and review the results. With a little practice and careful permission management, Codex can become a useful part of your everyday development routine.
