Guide
Is Codex free?
Yes, a little, on ChatGPT's free plan. Where the free part ends, what students get, and the ways to run it for nothing.
Partly. As of October 2026, OpenAI includes Codex on every ChatGPT plan, Free and Go too, but the free version is narrow: GPT-6 Luna, OpenAI's smallest current model, in the ChatGPT desktop app, with usage limits OpenAI doesn't publish. Codex Cloud and the stronger models start with Plus, at $20 a month. The Codex CLI itself is open source under Apache 2.0 and free to download; with an API key you pay per token, or you can point it at local models through Ollama or LM Studio. Verified university students in the US and Canada can get $100 in Codex credits.
Key takeaways
- Free and Go get GPT-6 Luna in the desktop app, since September 22, 2026, with no Codex Cloud and no published limits.
- Plus ($20) adds Codex Cloud, the CLI, the IDE extension, code review and Slack, with GPT-6.1 Sol: roughly 15 to 160 Sol messages every five hours.
- No plan is unlimited. Pro has no five-hour limit, but weekly limits may apply.
- Students: $100 in Codex credits in the US and Canada, and US college students can claim four months of Plus free until October 31.
- Poly's free tier runs the real Codex with GPT-6 Luna in a browser.
| Option | Cost | What you get | Catch |
|---|---|---|---|
| ChatGPT Free or Go | $0, or $8 a month | GPT-6 Luna in the desktop app | No Codex Cloud; limits unpublished |
| ChatGPT Plus | $20 a month | Codex Cloud, CLI, IDE, code review; GPT-6.1 Sol | Five-hour and weekly limits |
| ChatGPT Pro | $100, $200 or $500 a month | No five-hour limit | Weekly limits may apply |
| Business seat | $20 to $25 a seat | Codex and Work in every seat | Two-seat minimum |
| API key | Per token | CLI, SDK and IDE extension | No cloud features |
| Codex for Students | Free, $100 in credits | Codex credits for 12 months | US and Canadian university students |
| CLI with --oss | Free on your own computer | Codex with local models | Not OpenAI's models |
| Poly free tier | $0, 50 credits | Real Codex with GPT-6 Luna, in a browser | Then $20 or $50 a month |
Is Codex free with ChatGPT?
Yes, in a limited way. OpenAI's help article says Codex is included across ChatGPT plans, including Free and Go, with usage limits that vary by plan, and that Codex Cloud is not included with Free or Go. The plan cards describe the free version as GPT-6 Luna at standard speed in the desktop app, which OpenAI's changelog dates to September 22, 2026. OpenAI publishes no message limits for Free or Go; its pricing page says only "limited Codex access."
OpenAI's pages don't fully agree: its pricing table and the VS Code extension's listing still describe the CLI and IDE extension as for Plus and up. So we can confirm only the desktop app for Free and Go.
What does ChatGPT Plus add?
Plus, at $20 a month, adds Codex on the web, in the CLI, the IDE extension and iOS, plus Codex Cloud, code review on GitHub and Slack. OpenAI's estimates for local messages every five hours on Plus:
- GPT-6 Astra: 5 to 45.
- GPT-6.1 Sol: 15 to 160.
- GPT-6 Sol: 15 to 150.
- GPT-6 Luna: 350 to 3,000.
Local messages and cloud tasks share the allowance, weekly limits may also apply, and cloud tasks use more.
Is any Codex plan free and unlimited?
No. Pro ($100, $200 or $500 a month) has no five-hour limit but doesn't rule out weekly limits (OpenAI). Enterprise and Edu with flexible pricing have no fixed limits because usage is paid for with credits. Fast mode uses the allowance 2.5 times faster.
Is Codex free for students?
- Codex for Students: verified university students in the US or Canada get $100 in ChatGPT credits for Codex, which expire 12 months after they're granted. They need a Free, Go, Plus or Pro account; the credits aren't for the API (OpenAI).
- ChatGPT for college students: US college students verified through SheerID can claim four months of Plus free until October 31, 2026; it renews at $20 a month (OpenAI).
- ChatGPT Edu is sold to schools.
Is the Codex CLI open source?
Yes. The Codex CLI is open source under the Apache 2.0 license and installs through npm, Homebrew or a script. The IDE extension is free to install but not open source. You can sign in with an API key and pay standard API rates per token, without cloud features such as GitHub review and Slack; we found no standing offer of free API credits. Maintainers of open-source projects can apply to Codex for OSS for API credits and six months of Pro.
Can you run Codex with local models?
Yes. The --oss flag runs Codex against models served by Ollama or LM Studio on your own computer, for free (OpenAI). Other providers need an endpoint that speaks OpenAI's Responses API. The model doing the work is then whatever you run, not OpenAI's.
How can you use Codex free in a browser?
Poly (usepoly.co) runs the real Codex for GPT turns, in a sandbox on its servers, inside a browser room. The free tier includes GPT-6 Luna, plus Claude Sonnet 5.5 and a free model from each of the other labs, with 50 credits and no card; there's nothing to install, and you can invite others into the same room. When the credits run out, Pro is $20 a month.
For one person using Codex every day, ChatGPT Plus buys more. Poly is built for working with it together. Claude's side of the question is Is Claude Code free?, and teams should see Codex for teams.
Common questions
Is Codex free with ChatGPT Plus?
Yes. Plus, at $20 a month, includes Codex in the desktop app, CLI, IDE extension, web and Codex Cloud, with five-hour and weekly usage limits.
Can I use Codex on the free ChatGPT plan?
Yes, in a limited way: ChatGPT Free and Go include Codex with GPT-6 Luna in the desktop app, with limits OpenAI doesn't publish. Codex Cloud needs Plus or higher.
Is Codex free for students?
Verified university students in the US and Canada can get $100 in Codex credits that last 12 months, and US college students can claim four months of ChatGPT Plus free until October 31, 2026.
Is the Codex CLI free?
It's a free, open-source download under Apache 2.0. To run it you sign in with a ChatGPT plan or an API key, or point it at local models with the --oss flag.