Codex is OpenAI’s AI builder. You describe what you want in plain language, and it reads the files in a folder on your computer, edits them, runs the commands a developer would run, and shows you what changed. It is the same kind of tool as Claude Code, from the company behind ChatGPT. It comes with every ChatGPT plan, including the free one, which makes it the no-card way to try this way of working. It is not a website builder like Lovable or Base44, and it does not host anything.
What “Codex” means inside ChatGPT
The name confuses people because OpenAI has used it twice. Years ago, Codex was a model that turned English into code, the one under the first GitHub Copilot. Since 2025 it has meant the agent: the thing that acts in your files rather than the thing that suggests a line.
Today it shows up in four places, all tied to one ChatGPT account. The ChatGPT desktop app has two modes, which OpenAI’s docs describe as ChatGPT for “Create, learn, and explore” and Codex for “Build, debug, and ship.” Codex cloud runs in the browser on a copy of your code kept on GitHub or GitLab and hands back changes for you to review. Codex CLI is the terminal version. And the Codex extension sits inside code editors like VS Code and Cursor. For someone who cannot code, the desktop app is the friendly one: a window, a folder, a conversation.
How to install it on a Mac or on Windows
The desktop app needs no terminal, and every step below is from OpenAI’s own pages as of today.
On a Mac:
- Download the ChatGPT desktop app from chatgpt.com/download and open it.
- Sign in with your ChatGPT account. A free account works.
- Open a folder. Pick an empty one on your Desktop.
- Switch the mode from ChatGPT to Codex and describe what you want built.
On Windows:
- Install the ChatGPT app from the Microsoft Store, or from chatgpt.com/download.
- Install Git for Windows from git-scm.com, accepting every default. OpenAI’s docs say Git “powers the review panel” that lets you inspect and undo changes.
- Open the app, sign in with your ChatGPT account, open a folder, and switch the mode to Codex.
You do not need WSL, the Linux layer some forum posts mention. The app uses the Windows-native agent by default.
If you would rather have the terminal version, OpenAI gives one line per system. On a Mac, open Terminal and paste curl -fsSL https://chatgpt.com/codex/install.sh | sh. On Windows, open PowerShell and paste powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex". Then type codex while inside your project folder and choose Sign in with ChatGPT. If you want nothing installed, Codex cloud runs in the browser, but it needs your code on GitHub or GitLab first.
What it costs in shape, and what it does not do
Codex is included in the ChatGPT Free plan and in every paid plan. What changes with the plan is how much you can do before you hit a limit. OpenAI meters it in time windows: an allowance per five-hour window, and a weekly one on top, shared between the desktop app and the cloud version and with ChatGPT’s other agent features. On the free plan the allowance is small, and OpenAI describes it as enough to “explore Codex capabilities on quick coding tasks.” When you hit a limit you wait for the reset, upgrade, or on some paid plans add credits. None of this is per-message credits in the Lovable sense: a wasted message is a slice of a window that comes back, not money gone.
One trap: some tutorials have you sign in with an OpenAI API key instead of your ChatGPT account. OpenAI’s docs say that bills your platform account at API rates, separate from any subscription, and some features are unavailable that way. If you paste a key, you have switched from an allowance to a meter.
Codex also does not do the things a browser builder did for you. It does not host your app, and it comes with no database, no login, no preview pane and no Publish button. You run the app on your computer while you build it, and putting it on the internet is a separate service and a separate step.
Codex vs Claude Code: the differences, not a winner
The shape is the same. Both read, edit and run in a folder on your computer. Both take a goal in plain language. Both keep risky actions in check, Codex with a sandbox and Claude Code with a permission mode that can ask before every change. Both have a cloud version, a terminal version and an editor extension. Both makers’ docs point you to Git, the tool that keeps saved versions of your project. The instructions you type are the same words in either one.
| Codex | Claude Code | |
|---|---|---|
| Who makes it | OpenAI | Anthropic |
| How you get it | Included in every ChatGPT plan, free included | Included in paid Claude plans; no free tier |
| The desktop app | The ChatGPT desktop app, switched to Codex mode | The Claude desktop app, on its Code tab |
| How usage is metered | Five-hour windows plus a weekly limit, shared with ChatGPT’s other agent features | Time windows shared with the Claude chat app |
| When you hit the limit | Wait, upgrade, or add credits on some paid plans | Wait, or switch on usage credits on a paid plan |
| Paying with an API key instead | Bills your OpenAI platform account at API rates | Bills the key at usage rates instead of the subscription |
For a non-coder, three things decide it. First, free entry: Codex has one and Claude Code does not. Second, each tool comes with its maker’s chat subscription, so most people already own one of them. Third, the models: each runs its maker’s, both change every few weeks, and anyone naming a winner today is describing last month. Pick the one you can open tonight.
You can learn more, and get the full prompts and the decision tables, in our course: Lesson 1, How to Direct Your AI Builder. The first lesson is free, no card, and every prompt in it works in Codex too.
In the next ten minutes, if you pay for ChatGPT or for nothing, install the desktop app, sign in, and point it at an empty folder on your Desktop. If you pay for Claude, install Claude Code instead. Either way, decide on the smallest thing you actually want, and describe what should happen when it works.