OpenAI Codex – Development and Coding AI Tool
OpenAI Codex Review
Verdict
- Who it’s for: People who write code and want an OpenAI coding agent to help them write, review and ship it.
- Best thing: You can give it hard engineering jobs, from hard-to-find bugs to complex refactors and new features.
- Good to know: How far your usage goes depends on things like the model, how complex the task is and where it runs.
- Verdict: Worth trying if you write code and already use ChatGPT, since Codex is included across ChatGPT plans, but how much you can use it varies by plan.
What Is Codex?
Codex is OpenAI’s coding agent. It helps with writing, reviewing and shipping code, and is available through several ChatGPT-connected clients.
Codex can take on engineering tasks such as hard-to-find bugs, complex refactors and new features.
Overview
Codex can work on hard-to-find bugs, complex refactors and new features.
The product supports parallel agents, with tools to check work and let you follow progress.
Codex Cloud tasks can continue while your computer is asleep.
Codex automatically reviews pull requests, surfaces findings and answers questions.
How Codex Works
Launch your preferred Codex client and follow its instructions to sign in with ChatGPT.
For terminal work, open the project directory, run the Codex CLI and describe the task.
When agents are working, you can follow their progress, steer them and review their results in one place.
For cloud tasks, create and publish an environment on desktop or web, then start or continue tasks from supported devices.
Practical Workflow Integration
Codex is available through ChatGPT, an editor and the terminal, connected by a ChatGPT account.
Plugins connect tools and add specialized capabilities, giving Codex context and access to take action across apps.
Business and Enterprise/Edu workspace admins and owners manage plugin installation in Admin console.
Key Features
- Engineering tasks: Codex can work on hard-to-find bugs, complex refactors and new features.
- Parallel agents: It can run multiple agents in parallel and let you follow and steer their work.
- Cloud tasks: Cloud tasks can continue while your computer is asleep.
- Pull request reviews: Codex can review pull requests, surface findings and answer questions.
- CLI: The Codex CLI includes agent and multi-agent tools, worktrees and usage statistics.
- Plugins: Plugins can connect Codex with tools and add specialised capabilities.
- Automations: The Codex app can run scheduled tasks using instructions and optional skills, with results placed in a review queue.
Market Positioning
Codex can be used across ChatGPT, your editor and the terminal, all connected by your ChatGPT account.
Codex runs many agents in parallel, using computer and browser tools to verify work.
Enterprise cloud access is off by default for workspaces that have not enabled it.
Best Case Scenarios
- Refactoring: Use Codex to help with complex refactors or new features.
- Parallel work: Codex runs many agents in parallel and lets you follow progress, steer agents and review results in one place.
- Code review: Codex automatically reviews pull requests, surfaces findings and answers questions.
- Long-running cloud work: Cloud tasks can continue while your computer is asleep.
Example Use Cases and Prompts
- Where to start: For terminal work, open your project directory and type “codex” in the terminal, then describe the task.
- Bug fixing: Codex is presented as suitable for engineering problems such as hard-to-find bugs.
- “Your job is to add new features so the game matches the original more closely. First, play the game and identify what’s missing vs. the original. Then pick a few missing features and implement them. After each feature, thoroughly test it by playing the game and confirm it works. If you notice any bugs while playing, prioritize fixing them too.”
Power Prompt Library
- “Build a minimal pre-race flow with only: Track (8), Character (8), Difficulty (Chill/Standard/Mean), optional Mirror Mode, optional Allow Clones, and Start Race, plus an Options menu and an in-race pause menu (Resume / Restart / Quit).”
Limitations
- Cloud eligibility: Codex Cloud is not included with Free or Go plans.
- Workspace controls: Enterprise cloud access is off by default unless a workspace enables it.
- Variable usage: How much usage a task consumes depends on factors such as its complexity, model and tools.
- Browser access: Full CDP access lets Codex inspect and control sensitive browser internals that may put your data at risk, and Codex asks for explicit approval before using it to inspect a website.
Troubleshooting and Mistakes to Avoid
- Check usage: If you are near a limit, check Settings or your usage dashboard; in an active CLI session, enter “/status”.
- Windows diagnostics: Run codex doctor in the Codex CLI for diagnostics covering startup, connectivity and performance issues.
- Workspace access: If an action is unavailable, ask a workspace administrator to check your access.
- Review changes: Read generated changes carefully and run the checks that matter for your project before relying on them.
Who Uses It
Cisco: Cisco used Codex to write most of AI Defense and nearly every new feature it was building.
These results come from vendor-published case studies, and results for individuals may be more modest.
Similar Tools
- Cursor: Cursor uses project-wide context to suggest changes across multiple files or modules.
- GitHub Copilot: GitHub Copilot suggests code as you type, helping developers complete routine work faster.
- Replit: Replit combines coding assistance, hosting, debugging and collaboration to help users build and deploy applications rapidly.
- Windsurf: Windsurf is for professional developers who want AI help without sacrificing control over their workflow.
Quick Start Checklist
- Sign in to Codex with your ChatGPT account.
- Choose a supported client, such as the desktop app, CLI, IDE extension or web.
- For CLI use, open your project directory, run “codex” and describe the task.
- Start with a clear, manageable task and explain what a successful result should look like.
- Review the proposed work before using it in your project.
Frequently Asked Questions
Which Codex clients can I use?
The listed clients include the ChatGPT desktop app, Codex CLI, Codex IDE extension and Codex web.
Can I use Codex in an IDE?
Yes. The Codex VS Code extension works with most VS Code forks; for other IDEs, you can use the CLI in the IDE terminal.
Is Codex Cloud available on every plan?
No. It is available to eligible Plus, Pro, Business, Enterprise, Healthcare and Education accounts, but not Free or Go.
Does OpenAI train on business Codex usage?
By default, OpenAI does not use inputs or outputs from its products for business users to improve its models.
Does Codex usage depend on the task?
Yes. Usage depends on factors including the model, task complexity, context, reasoning, speed and tools.
When to Choose Another Tool
- GitHub Copilot: GitHub Copilot suggests code as you type, helping developers complete routine work faster.
- Replit: Replit combines coding assistance, hosting, debugging and collaboration to help users build and deploy applications rapidly.
- If you do not want to review or test AI-generated work, a coding assistant may not be the right fit.
Summary
Codex is available across ChatGPT, your editor and the terminal.
Last checked: October 2026
