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Set up your AI tool

Install Codex

Codex is OpenAI's AI for building software. It comes inside the ChatGPT desktop app, and it reads your package's rules the same way Claude Code does.

About 10 minutesMac and WindowsLast checked

Why the ChatGPT desktop app

Since July 2026, Codex lives in the ChatGPT app for Mac and Windows, next to the usual chat. It's the easiest way in: no Terminal, and it can work in a folder on your computer, which ChatGPT on the web can't.

Have these ready

  • A Mac, or a PC with Windows 11. An up-to-date Windows 10 works too.
  • The email address for your ChatGPT account. Use the business's email, so the account stays with the business.
  • A paid ChatGPT plan. Plus is $20 a month. The Free and Go plans include only a little Codex, on a smaller model.

Steps

  1. Step 1: Open ChatGPT's download page

    Go to chatgpt.com/download.

    You should see: Downloads for Mac and for Windows.

  2. Step 2: Download the app for your computer

    Mac
    Click Download for macOS (Apple Silicon). On an older Mac with an Intel chip, choose Download for macOS (Intel).
    Windows
    Click Download for Windows. It opens the Microsoft Store: click Get or Install.

    You should see: On a Mac, a file ending in .dmg in your Downloads folder. On Windows, the Store installing ChatGPT.

    If it looks different: Not sure which Mac you have? Click the Apple menu, then About This Mac. An Apple M chip means Apple Silicon; a processor that says Intel means Intel.

  3. Step 3: Install it

    Mac
    Double-click the .dmg file, then drag the app onto the Applications folder.
    Windows
    The Store installs it for you. Wait until it says it's done.

    You should see: ChatGPT in your Applications folder on a Mac, or in the Start menu on Windows.

    If it looks different: If you see two ChatGPT apps, open the newest one. An older Codex app updates into ChatGPT.

  4. Step 4: Open ChatGPT and sign in

    Click Continue to sign in, then finish signing in in the browser window that opens.

    You should see: The ChatGPT app, signed in.

    If it looks different: If your Mac asks whether you're sure you want to open an app downloaded from the internet, click Open.

  5. Step 5: Choose the Plus plan

    Go to chatgpt.com/pricing, choose Plus and pay with your card. Pay on that page only: Codex never asks for a card in a chat.

    You should see: The pricing page shows Plus as your plan.

  6. Step 6: Switch to Codex

    In the ChatGPT app, open the menu at the top and choose Codex.

    You should see: Codex's screen, with Add new project next to Chats in the sidebar.

    If it looks different: No Codex in the menu? Quit the app, open it again and check for updates. Codex needs the newest ChatGPT app.

If you often reach your usage limit later on, the Pro plan gives you more. Most builds don't need it at the start.