How to Install OpenAI Codex CLI: Complete Setup Guide for 2025

Mar 25, 2026

Purpose

This post demonstrates how to install OpenAI Codex CLI in your AI programming tools like Cursor, Trae, or VS Code. The most important thing I learned: you don’t need an API key.

The Problem

When I first heard about OpenAI Codex CLI, I was confused about how to install it. I thought I needed to:

Sign up for OpenAI API access
Generate an API key
Install some CLI tool via npm or pip
Configure environment variables

I spent an hour digging through documentation, only to discover I was completely wrong. The “CLI” in Codex CLI doesn’t mean a command-line tool you install. It means Codex integrates directly into your IDE as a plugin.

What You Actually Need

Before trying to install Codex, I needed to understand the prerequisites:

[✓] ChatGPT Plus, Business, or Pro account ($20/month minimum)
[✓] AI programming tool (Cursor, Trae, Qoder, Kiro, or VS Code)
[✓] Network access to OpenAI services
[✗] API key - NOT REQUIRED!

The last item surprised me. OpenAI announced that ChatGPT Plus users can use Codex CLI without an API key. You simply log in with your ChatGPT account to authorize.

Step 1: Choose Your AI Programming Tool

Codex works with several AI-focused IDEs. Here are the main options:

Tool	Description	Best For
Cursor	Popular AI-native IDE	General development
Trae	AI IDE by ByteDance	Web development
Qoder	AI coding assistant	Quick prototyping
Kiro	AI-powered editor	Lightweight coding

I use Cursor, so I’ll show the steps for that. The process is similar for other tools.

Step 2: Install the Codex Plugin

In Cursor (or your chosen IDE), open the extension marketplace:

1. Open your IDE
2. Go to Extensions/Plugins marketplace
3. Search for "OpenAI Codex" or just "Codex"
4. Click Install
5. Wait for installation to complete

Here’s what the search looks like:

Search query: "OpenAI Codex"
or: "Codex"

Look for the official OpenAI icon

Step 3: Authorize with ChatGPT Account

After installation, I needed to authorize:

1. Click the OpenAI icon in the sidebar
2. A browser window opens
3. Log in with your ChatGPT Plus account
4. Authorize the IDE to access Codex
5. Return to your IDE - Codex is now active

No API key configuration. No environment variables. Just log in and start coding.

Step 4: Configure Codex Preferences

Once authorized, I configured a few preferences:

{
  "languagePreference": "English",
  "codeStyle": "project-standards",
  "responseSpeed": "balanced",
  "contextMemory": "enabled"
}

These settings help Codex understand my coding style and respond appropriately.

Common Installation Mistakes

I made several mistakes before getting Codex working:

Mistake 1: Using Free ChatGPT Account

"Your account does not have access to Codex.
Please upgrade to ChatGPT Plus, Business, or Pro."

Codex requires a paid ChatGPT subscription. The free tier doesn’t include CLI access.

Mistake 2: Network Issues

If you’re in a region with restricted access to OpenAI services, you’ll see:

"Unable to connect to OpenAI servers.
Please check your network configuration."

This is the most common issue for users in China and other restricted regions. You need a reliable network path to OpenAI.

Mistake 3: Looking for CLI Installation

# This doesn't exist
npm install -g openai-codex-cli

# This doesn't exist either
pip install openai-codex

# There is NO command-line installation!

The “CLI” name is misleading. It’s not a command-line tool. It’s a plugin that integrates into your IDE.

Why Codex CLI Matters

After using Codex for a few weeks, I understand why developers are excited about it:

- Powered by GPT-5.3-Codex model
- Deep code understanding and generation
- Context-aware refactoring suggestions
- Bug detection and fixes
- Documentation generation
- Multi-file code analysis

Compared to other AI coding assistants, Codex excels at understanding large codebases and providing contextually relevant suggestions.

Comparison with Other AI Coding Tools

Feature	Codex CLI	GitHub Copilot	Claude Code
Price	$20/month (ChatGPT Plus)	$10-19/month	$20/month
API Key Required	No	No	No
Deep Reasoning	Excellent	Good	Excellent
Multi-file Context	Strong	Moderate	Strong
Agent Workflows	Limited	Limited	Strong

I found Codex particularly good for deep code analysis and refactoring. The context retention is impressive - it remembers what we discussed earlier in the session.

Summary

In this post, I showed how to install OpenAI Codex CLI in AI programming tools. The key insights are:

No API key needed - Just log in with your ChatGPT Plus account
It’s a plugin, not a CLI tool - Install from your IDE’s extension marketplace
ChatGPT Plus required - Free accounts don’t have access
Network matters - Ensure reliable access to OpenAI services

The installation is straightforward once you understand what Codex CLI actually is. Skip the API key setup, install the plugin, authorize with your ChatGPT account, and start coding with AI assistance.

Final Words + More Resources

My intention with this article was to help others share my knowledge and experience. If you want to contact me, you can contact by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

👨‍💻 OpenAI Codex Documentation
👨‍💻 Cursor IDE
👨‍💻 ChatGPT Plus

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!