Codex App Reference

The complete guide to OpenAI's Codex — CLI, desktop app, skills, automations, and pro tips for agentic coding.

GPT-5.3-CodexOpen Source CLI

npm (all platforms)

npm install -g @openai/codex

Homebrew (macOS)

brew install codex

Desktop app (macOS)

codex app

Opens the native macOS app

🖥️

Desktop App

Native macOS app with worktrees, automations, and project sidebar

⌨️

CLI

Open-source Rust-based agent — runs in any terminal, any OS

🔌

IDE Extension

VS Code & JetBrains plugin sharing MCP config with the CLI

🌐

Web

Cloud-based interface with remote environment and browser access

Surfaces (app/CLI/IDE/web)

Pre-made skills

∞

Custom automations

Free CLI

Open-source on GitHub

GPT-5.3-Codex

The flagship model — available to all paid ChatGPT plans

Current default

Reasoning

Frontier-class — stronger than GPT-5.2-Codex

Speed

25% faster than previous generation

Collaboration

Real-time steering + frequent progress updates

ChatGPT Pro subscribers also get access to GPT-5.3-Codex-Spark — a faster variant optimized for quick, iterative tasks.

What is Codex?

Codex is OpenAI's agentic coding partner — a system that can write features, fix bugs, review code, and orchestrate multi-agent workflows across your repositories. The CLI is open-source Rust, runs locally, and calls OpenAI's cloud models for inference. Your code stays on your machine; AI reasoning happens in OpenAI's cloud. The desktop app adds worktrees, project management, automations, and a native macOS UI. Included with ChatGPT Plus, Pro, Business, Edu, and Enterprise plans.