Codex is only partly free. The ChatGPT Free plan gives limited access to it, which OpenAI describes as a chance to try the tool on simple coding tasks. The CLI you install on your computer is open source and costs nothing on any plan. What stays paid is access to the model that does the actual work, either through a ChatGPT subscription or by paying for tokens directly.
What the ChatGPT Free plan gives you
OpenAI states outright that Codex is available on every ChatGPT plan, Free included. On the free plan that means a first look at Codex on simple tasks, with limits cut down compared with the paid plans. The Go plan at $8 a month widens the limits, but access to Codex there is limited too, and nothing is unlimited.
The takeaway is short. A single small task is worth trying on Free: download Codex and see. For regular work, and even more for a real project, the Free and Go limits last only a short while. The article Codex limits and what to do when they run out explains how both usage windows work and what to do once you hit the cap.
The CLI is free, the model is not
This is where most of the confusion about "Codex free" comes from. Codex CLI installs with npm install -g @openai/codex or the official installer script, and it is an open tool: using the interface costs nothing. You pay for the calls to the model that carries out tasks through that CLI.
There are two ways to pay. The first is a ChatGPT subscription (Free, Go, Plus, Pro or Business), which opens the model through OpenAI's cloud with limits that depend on the plan. The second is an API key billed as you go. The same CLI can be set up to pay for tokens through API billing, and then you need no ChatGPT subscription at all. That route is covered in Codex CLI with an API key instead of a subscription.
Tokens are not free, but they remove the 5-hour and weekly windows. You pay for exactly what you used, and time does not cap you.
What it costs when it is not free
Reference prices for ChatGPT plans at the time of writing (September 2026): Go from $8 a month, Plus from $20, Pro from $100 (the 5x plan) and $200 (the 20x plan, temporarily closed to new sign-ups at the time of writing). Check the exact figures and terms of a plan on OpenAI's official pricing page, because the terms change.
An option for Russia: from $1, no ChatGPT subscription
Paying for a ChatGPT subscription with a card from Russia often fails: OpenAI does not accept Russian cards. An API key fits that case. Through codexkey, Codex CLI connects to GPT-5.6 models, you can pay with a ruble card or through SBP (the Russian Faster Payments System), and the balance tops up from $1.
The setup is almost the same as with a direct OpenAI key. Only the provider in config.toml changes:
model_provider = "codexkey"
model_reasoning_effort = "medium"
model = "gpt-5.6-luna"
[model_providers.codexkey]
name = "codexkey"
base_url = "https://api.codexkey.online/v1"
env_key = "CODEX_KEY"
gpt-5.6-luna suits the cheapest, fastest tasks, and gpt-5.6-sol is better for complex agentic work on code. One caveat: codexkey currently offers the GPT-5.6 line, not the newest GPT-6, which OpenAI has been rolling out in Codex gradually since September 2026. For most coding tasks the difference is small, but if you specifically need GPT-6, the only route right now is a direct ChatGPT subscription from OpenAI.
Step-by-step setup of config.toml and the key variable on Windows, Mac and Linux is in the Codex guide.
Subscription or per-token billing
A ChatGPT subscription makes sense if you already work with GPT-6 in the chat, want one bill for everything and your card goes through without trouble. Per-token billing makes sense in three cases: your card is not accepted directly, you use Codex irregularly and a flat monthly plan would not pay back, or you want to track spend per project without a shared window limit.
Neither option is "more free" than the other. Both cost money, and they differ in how you pay and in what happens when the limit runs out.
FAQ
Can I use Codex without registering at all?
No. Codex through ChatGPT needs an OpenAI account, and the API-key route needs a separate registration with whoever issues the key, whether that is platform.openai.com or a third-party gateway such as codexkey.
Is Codex AI completely free, or is that a myth?
A myth, if you take it literally. The CLI is open and asks for no money, but the model that performs the tasks needs a ChatGPT subscription or API payment. No plan gives permanent, fully free work with the model.
Is the free plan enough for a learning project?
To get used to the interface and finish a couple of small tasks, yes. With several sessions a day the Free limits run out fast, and you have to wait for the window to reset or move to a paid option.
How is open source Codex CLI different from free use?
Open source means you can study how the tool works, build it yourself or modify it. It does not cancel the cost of model requests: in most scenarios they cost money, and only the limited Free allowance is free.
Is there a way to use Codex in 2026 without OpenAI altogether?
No. Codex the product belongs to OpenAI and works only with its models. You can, however, connect the CLI through a third-party API key such as codexkey: no ChatGPT account is needed, and you pay for model tokens, not for a subscription.