What is OpenAI Codex?

Codex is OpenAI’s entry in the category of AI agents that do work rather than just answering. If you have read about Claude Code, the idea is the same: you describe a goal, and the tool takes steps to reach it.

What OpenAI says it is

The OpenAI Codex docs say you start with a goal, idea, or task, and ChatGPT can gather context, take action, and produce something useful. The documentation lists these places to use it:

• The ChatGPT desktop app
• The web browser
• The ChatGPT mobile app
• A command-line interface (CLI)
• An IDE extension
• Cloud environments

Plans and limits change over time, so check OpenAI’s current pricing page before deciding. The OpenAI Codex pricing page says ChatGPT Work and Codex are included in your ChatGPT Free, Go, Plus, Pro, Business, Edu, or Enterprise plan.

What the documentation says about safety and limits

• Network off by default OpenAI states that by default, the agent runs with network access turned off.
• A sandbox and an approval policy The OpenAI Codex security docs say Codex runs locally in a sandbox enforced by the operating system that limits what it can touch, typically to the current workspace, plus an approval policy that controls when it must stop and ask you before acting.
• Undo points The CLI quickstart advises you to create Git checkpoints before and after a task so you can revert changes.
• Local message estimates The OpenAI Codex pricing page says its estimates are local messages per five-hour period for Plus and Standard Business. The OpenAI Codex pricing page says Pro plans currently have no five-hour limit. The OpenAI Codex pricing page says these estimates are not fixed message limits.

How it works in practice

Two features matter for how people use it:

1. It acts, not just replies. Instead of a paragraph about how to fix something, it edits the files or produces the deliverable.
2. It can work in the background. In our class, we show how Codex handles tasks asynchronously: you give it a task, go do something else, and check the results later. The OpenAI Codex cloud docs say each task has its own workspace and can keep working while your computer is asleep. The OpenAI Codex cloud docs say you inspect changed files and check results, request follow-up changes, and commit or open a pull request when you’re ready.

What it is for outside software

Software developers use it for writing and reviewing code. Non-developers can use the same capability for tasks that can be expressed as “read these files, produce this output”:

• Building a script that consolidates spreadsheets.
• Producing a formatted report from raw exports.
• Automating repetitive file handling.

For a plain-English introduction to this style of work, see what AI agents are.

Codex or Claude Code?

They overlap heavily. The choice often comes down to which company’s ecosystem you already pay for, your company’s approved tools, and which one you find easier to work with. Neither is right for everyone. Our comparison of Claude Code and Codex goes into the differences.

Cautions

Like any agent, Codex can make mistakes when it edits files or runs commands. Use copies, review what it does and keep sensitive data out unless your company’s policy permits it. See whether it is safe to put company data in ChatGPT.

In the class

Learn AI Fast covers Codex alongside Claude Code in the first day’s tools session, so you can try both on real tasks and see which suits your work.

Sources

• OpenAI, Codex overview: “Start with a goal, idea, or task. ChatGPT can gather context, take action, and produce something useful.”
• OpenAI, Codex pricing: “ChatGPT Work and Codex are included in your ChatGPT Free, Go, Plus, Pro, Business, Edu, or Enterprise plan”
• OpenAI, Codex agent approvals and security: “By default, the agent runs with network access turned off”
• OpenAI, Codex agent approvals and security: “Codex uses an OS-enforced sandbox that limits what it can touch (typically to the current workspace), plus an approval policy that controls when it must stop and ask you before acting”
• OpenAI, Codex CLI: “Create Git checkpoints before and after a task so you can revert changes”
• OpenAI, Codex pricing: “The estimates below show local messages per five-hour period for Plus and Standard Business”
• OpenAI, Codex pricing: “Pro plans currently have no five-hour limit”
• OpenAI, Codex pricing: “These estimates are not fixed message limits”
• OpenAI, Codex cloud: “Each task has its own workspace and can keep working while your computer is asleep”
• OpenAI, Codex cloud: “Inspect changed files and check results, request follow-up changes, and commit or open a pull request when you’re ready”