Codex for Builders

Builder | AI For Coding

AI-powered coding agent for faster, higher-quality development.

What is Codex?

Codex is OpenAI’s agentic software teammate designed to accelerate builder productivity and ultimately enable fully autonomous execution of software tasks.

Where can you use Codex?

Codex works where developers build and write code. Codex is one unified agent, one product, with clients for the places developers work.

• In your terminal with the open source Codex CLI
• On the web with Codex web
• On your phone, with the Codex tab in the ChatGPT iOS app
• In your IDE with the Codex IDE extension
• In GitHub with the GitHub integration

What do builders use Codex for?

• Familiarizing with new or large codebases.
• Drafting technical designs and docs
• Debugging issues and exploring solutions
• Planning and implementing migrations and new features
• Leveraging Codex CLI’s headless mode for more advanced use cases around CI/CD automation

How does Codex tie in with my ChatGPT plan?

You can sign in to the CLI and IDE directly through your ChatGPT plan, eliminating API key setup. Codex web is available in ChatGPT as well after you connect your GitHub account.

What is the best model to use with Codex?

Codex now leverages the recently launched GPT-5-Codex model, a version of GPT-5, that is built for agentic coding use cases. A few highlights:

• More steerable: Writes high-quality code on complex engineering tasks without lengthy instructions.
• Adaptive reasoning level: Adjusts reasoning time to task complexity. It’s snappy in interactive sessions and can work independently for multiple hours.
• Excellent at code review: Trained to conduct code reviews, navigate codebases and run code and tests to validate correctness.
• Supports image input: Use images or screenshots to guide frontend work, visually inspecting progress and catching issues in the cloud.
• Purpose-built for coding: Purpose-built for Codex CLI, IDE, cloud, and GitHub, and focuses on agentic coding tasks.

Key benefits for builders

• Code generation from natural language: Quickly scaffold projects, add features, or generate boilerplate code.
• Code understanding: Get clear explanations for complex logic and dependencies.
• Refactoring & optimization: Improve efficiency and maintainability without altering intended behavior.
• Multi-language support: Works across popular programming languages, frameworks, and libraries.
• Automating repetitive tasks: Offload well-scoped engineering work like refactoring, renaming, and writing tests to stay focused on higher-value work.

Core resources

• Codex 102 training workshop: Hands-on, task-based training that walks builders through using Codex in real development workflows, including the CLI, IDE integration, MCP, and code review patterns. Click "Join Room" and you'll be ready to dive in.
• Codex demo: Understand the basics of using Codex and understand how Codex’s IDE extension, Codex web, and code review work in unison to help builders accelerate their workflows.
• Codex overview & tips: Public documentation with capabilities, usage tips, and an overview video.
• Developers hub: Central resource for Codex docs, guides, and API references.
• How to use Codex with your ChatGPT plan: Step-by-step instructions on signing in and using Codex tools directly through your ChatGPT account.
• Codex web changelog: A running log of new features, improvements, and fixes in Codex web.
• How OpenAI uses Codex (PDF): OpenAI's best-practice guide on prompting for Codex, with examples from real workflows (see below). Experiencing slow loading? Download the file to view.

Get started today

• Explore the Codex Demo and Overview to see capabilities.
• Review How OpenAI Uses Codex and Developers Hub for practical prompting strategies.
• Apply Codex in your CLI, IDE, or GitHub workflows to generate, refactor, and understand code more effectively.

Table Of Contents

Codex for Builders | What is Codex? | Where can you use Codex? | What do builders use Codex for? | How does Codex tie in with my ChatGPT plan? | What is the best model to use with Codex? | Key benefits for builders | Core resources | Get started today

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