OpenAI Codex
Understand an existing codebase, make focused changes and investigate bugs with OpenAI’s coding agent.
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What can you use Codex for?
OpenAI describes Codex as a coding agent that helps write, review and debug software. It is useful when you already have a project and need help understanding a function, changing a feature or investigating a failure.
A useful first task
Our suggested starting point: “Explain where this project handles its contact form. Describe the files involved and suggest one small improvement. Do not edit anything yet.” This gives you a chance to check its understanding before requesting a change.
How does it work with your project?
The Codex CLI can inspect local files, edit code and run installed development tools from your terminal. You choose permissions and can inspect proposed commands and changes. If you prefer an editor, OpenAI also documents an IDE interface.
Before accepting a change
Read the changed files and run the checks relevant to your task. For a contact form, also try sending a message and checking what happens when required fields are empty.
Sources checked: 17 October 2026. See the official guides for current setup and access options.
