You are probably here because someone told you that you can now put an AI on your own computer, point it at your files, and get finished work back. This page explains what Codex actually is, whose it is, what it needs, how you start, and when you should not bother.
Everything checkable below comes from OpenAI's official documentation as it reads today; the links are at the bottom. If the words on your screen differ, trust your screen — these apps change often.
Codex is a working mode from OpenAI that lives inside the ChatGPT app. The official desktop docs describe the sequence as: install ChatGPT, sign in, choose where to work, and send your first message — and at that last step you "Choose ChatGPT or Codex". So it is not a separate product you buy; it is another gear inside the same app.
What makes it different from chatting with ChatGPT in a browser? The official wording is that it can use the files and context in the location you choose. In plain terms: you point it at one folder on your computer, and it can read what is in there and write into it. A chat window gives you back words. Codex leaves a file on your machine that you can open.
The word codex, outside computing, means an old manuscript bound as a book — which is why half your search results are about ancient texts. In software today, when people say Codex they almost always mean OpenAI's.
There is a second trap. On a Mac the installer you download from the official page is called Codex.dmg, but the app that ends up in your Applications folder is called ChatGPT. That is not a mistake — it is what we saw when we recorded our install lesson. Plenty of people assume they downloaded the wrong thing, search "Codex download" again, and install someone else's app with the same name.
No commands to memorise — on the desktop app it is all mouse clicks. There are only three things worth learning:
Once those three are set, the rest is plain language: tell it what you want, then open what it produced and check it.
Ignore the third-party "fast download" sites in the search results. The official route is the ChatGPT documentation site's desktop app page, which carries the macOS, Windows and Linux download buttons; the Mac button reads Download for macOS (Apple Silicon) today. If you want it step by step, we have a separate page on the official download and the first open.
First launch, in the order the official page gives it: open the app, sign in with your own ChatGPT account, choose where to work, send your first message. Signing in and entering codes is something only you should do — never hand those to anyone, and never leave them in a screenshot.
Straight answer: not every owner needs this. Three cases where you should skip it.
Codex only touches the folder you point it at. It does not go into your messaging apps, and it does not email a customer, sign anything or pay anything for you — the last press is always yours. That is a rule we teach and also plain common sense: a machine can take the work to the final step, but the final step belongs to the owner.
It also misreads things, and it will turn "the client hopes" into "the client requires" if you let it. So start in the ask-first mode and open what it made before you send it anywhere. Not sure any of this fits your trade? The free five-minute check is allowed to tell you that you don't need it.
The official pricing page states that ChatGPT Work and Codex are included in your ChatGPT Free, Go, Plus, Pro, Business, Edu or Enterprise plan, with different allowances per plan. Check the vendor page for today's prices and limits.
No. That is OpenAI's own Mac installer, and the installed app is ChatGPT. Codex is a mode inside it. Do not go back and search for another 'Codex download'.
No. On the desktop app it is clicking, choosing a folder, describing what you want in plain language, and checking the result. Our Build 39 install lesson goes from never having done it to your first success.
The official permissions page splits this into three modes and recommends starting with Ask for approval, which pauses before it acts. Pair that with an AGENTS.md rule saying originals must not be edited.
The two routes do very similar things; the differences are button names and which account plan you need. We compare them on a separate page for owners.
Sources (checked 2026-09-07):ChatGPT desktop app (official docs) · ChatGPT and Codex pricing · Codex permission modes · Custom instructions with AGENTS.md
Last checked: 2026-09-07