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Getting Started with Codex CLI

8 min readMar 2, 2026

Midjourney 7 AI-art. March 2026.

Learn what Codex CLI is, how to install it on Mac, Linux, and Windows, and take your first steps with this AI coding assistant that runs in your terminal.

TL;DR: Codex CLI is OpenAI’s coding agent for your terminal. Install via brew (Mac) or npm (universal). Authenticate with a ChatGPT subscription or API key. Start in read-only mode to explore safely. Part 1 of a 4-part series.

Introduction

Today, I want to introduce you to Codex CLI — a tool that has genuinely changed how I work with both code and writing.

If you have ever wished you could have an AI assistant that actually understands your project, can read your files, and help you make changes right from your terminal, Codex CLI is exactly that. It is not just another chatbot; it is designed to work inside your repository, understanding your code structure and helping you improve it safely.

In this series, I will walk you through everything you need to know to use the Codex CLI productively. Today’s post covers the fundamentals: what it is, how to install it, and how to take your first steps safely.

What Is Codex CLI?

Before we jump into installation, let me explain what Codex CLI is and why it differs from…

Elena Daehnhardt

Getting Started with Codex CLI

Introduction

What Is Codex CLI?

Written by Elena Daehnhardt

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