Codex

One agent for everywhere you code

Codex is OpenAI's coding agent for software development. ChatGPT Plus, Pro, Business, Edu, and Enterprise plans include Codex. It can help you:

Write code: Describe what you want to build, and Codex generates code that matches your intent, adapting to your existing project structure and conventions.
Understand unfamiliar codebases: Codex can read and explain complex or legacy code, helping you grasp how teams organize systems.
Review code: Codex analyzes code to identify potential bugs, logic errors, and unhandled edge cases.
Debug and fix problems: When something breaks, Codex helps trace failures, diagnose root causes, and suggest targeted fixes.
Automate development tasks: Codex can run repetitive workflows such as refactoring, testing, migrations, and setup tasks so you can focus on higher-level engineering work.

Get started with Codex →

Codex CLI showing a project sidebar, thread list, and review pane

Quickstart

Download and start building with Codex.

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Explore use cases

Get inspiration on what you can build with Codex.

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Community

Read community posts, explore meetups, and connect with Codex builders.

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Codex for Open Source

Apply or nominate maintainers for API credits, ChatGPT Pro with Codex, and selective Codex Security access.

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Quickstart

Every ChatGPT plan includes Codex. You can also use OpenAI API credits with an API key.

CLI (Recommended)

Install with PowerShell:

npm i -g @openai/codex

Or via Homebrew:

brew install codex

Run codex to authenticate and start working.

Cloud

Available at chatgpt.com/codex. Connect a GitHub repository, monitor tasks with logs, review diffs, and create pull requests directly.

Use Cases

Explore practical workflows. Key categories:

Production Systems — Navigate real codebases, make controlled changes, codify repeatable work
Web Development — Convert design inputs into responsive UI with fast iteration
Native Development — Build for iOS/macOS, refactor native UI
Game Development — Create games from initial playable loops to production quality
Productivity — Analyze data, integrate apps, transform insights into action

Featured examples: Review pull requests, build responsive designs, refactor codebases, create CLI tools, automate bug triage.

Prompting

Communicate with Codex by submitting prompts describing desired tasks.

Writing effective prompts

Codex produces higher-quality outputs when it can verify its work. Include reproduction steps and validation procedures. Break complex tasks into smaller, focused steps — they're easier to test and review.

Threads

A thread represents a single work session. Threads can run locally or in cloud environments. Local threads operate within sandboxes. Codex supports standalone chats using a managed threads directory (default: ~/.codex/threads).

Context

Context includes relevant files, images, and information Codex gathers during work. The system monitors context window limitations and can automatically compact context through summarization.

Models

gpt-5.4 (recommended) — Industry-leading coding capabilities with strong reasoning, tool use, and agentic workflows. Start here for most tasks.
gpt-5.4-mini — Streamlined variant for responsive coding tasks and subagents, prioritizing speed and efficiency.
gpt-5.3-codex — Industry-leading coding model for complex software engineering.
gpt-5.3-codex-spark — Research preview optimized for near-instant, real-time coding iteration. ChatGPT Pro only.
gpt-5.2 — Previous generation suited for coding and hard debugging tasks.

Configure default models via config.toml or select temporarily using CLI commands.