Codex is OpenAI's coding agent: an AI that helps people write, review and ship software, working from a terminal, a code editor or the cloud.
In plain words
Codex does more than suggest the next line. In the terminal, the open-source Codex CLI can explore a project, edit files and run the code. An extension puts it inside editors such as VS Code, Cursor and Windsurf. Codex Cloud runs tasks in a remote environment set up with your repositories; when it finishes, you check the changed files and results, then save them to the project or open a pull request. It is included with ChatGPT plans.
A quick example
Imagine a test in your project keeps failing. You open the project folder in a terminal, start Codex and ask it to find the cause. It reads the relevant files, suggests an edit, runs the tests again and shows you the change so you can decide whether to keep it.
Where you'll meet it
- Fixing bugs and adding features from the terminal or an editor.
- Handing longer coding tasks to run in the cloud.
- Reviewing code changes before they are merged.
Related
Sources
- DocsUsing Codex with your ChatGPT plan, OpenAI Help Center · read 29 Sept 2026
- Docsopenai/codex, OpenAI (GitHub) · read 29 Sept 2026
- DocsCodex CLI, OpenAI Developers · read 29 Sept 2026
- DocsCodex Cloud, OpenAI Developers · read 29 Sept 2026
Checked by WhatIsAI against the sources above · 11 Nov 2026. Spotted an error? Report it.