Explainer · updated Oct 10, 2026
Codex is OpenAI's coding agent, available as an open-source CLI, an IDE extension, a desktop app and a cloud agent. Usage is included in ChatGPT plans from Free to Enterprise, or billed at API rates.
Codex is OpenAI's coding agent. You describe a coding task in plain language, and the agent proposes code edits, pull-request style changes or review comments. The command-line version is open source and runs locally on your computer, so it works against the files in your own repository. The inputs are natural-language coding tasks, your local repository, and connected GitHub repositories. The outputs are code edits, review comments and command output from local runs, which you check yourself.
The same agent is also offered as an IDE extension, a desktop app, and a cloud-based agent on the web and iOS. Using any of them requires an account. Usage is included in ChatGPT plans, or you can pay API rates with an API key instead. Because the CLI is open source, you can inspect the code you run. Cloud-only features need a ChatGPT sign-in, and the desktop app gives a visual interface for people who prefer not to work in a terminal.
In the CLI and the IDE extension, Codex works on your local repository. You describe the change, Codex proposes edits, and you review and approve the ones you want to keep. You can then ask it to run your test command and check the output. Local sessions can handle larger jobs such as a refactor in an open repository, while quick questions and small changes suit any plan that includes the agent. Project conventions go into an AGENTS.md file, and external tools connect through MCP servers.
In the cloud, Codex works on GitHub-connected repositories, which allows features such as automatic code review and Slack integration. The CLI installs with an install script, npm or Homebrew. The IDE extension supports VS Code, Cursor and Windsurf. Codex on the web and iOS runs tasks in the cloud, so work can continue without your own machine, and the profile lists it for the Plus plan.
Codex usage comes with a ChatGPT plan. The profile lists Free at $0 per month, Go at $8 per month and Plus at $20 per month. Pro starts at $100 per month, with $100, $200 and $500 tiers; we could not confirm how those tiers map to usage. Pricing page content was not fully captured in our checks, so confirm current figures on the official pricing page before you subscribe. Plan details are on the OpenAI Codex pricing and ChatGPT pricing pages.
Business is $20 per user per month billed annually, or $25 billed monthly. Enterprise and Edu are contact sales. With an API key you pay API rates per token instead. Usage limits apply on every plan, and Free and Go list the desktop app only. Codex usage is shared with the ChatGPT plan you already have, so you do not need a separate subscription just to try it.
Codex fits people who already use ChatGPT and want one coding agent across a terminal, an editor, a desktop app and the web. It also suits developers who want a CLI plus a cloud agent, and teams that want automatic code review on connected GitHub repositories. A Free ChatGPT plan includes Codex, which makes it possible to try the agent before paying anything for it. For the closest rivals read what Claude Code is and what Gemini CLI is, then Codex vs Claude Code, ChatGPT vs GitHub Copilot and Claude vs ChatGPT; the Codex alternatives page, the Best AI agents list and the AI coding tools guide cover the rest.
It is a weaker fit if you want API-key billing and also need cloud features, because GitHub code review and Slack are not available with an API key. Heavy users should expect to hit plan usage limits. Privacy, training use and retention are not documented in the pages we checked. The docs navigation also lists sandboxing and agent approvals, but we did not read those pages, so we cannot describe how they work.
Our profile lists GitHub Copilot, Cursor, ChatGPT and Windsurf Editor as the alternatives to consider. Cursor and Windsurf are editors, while Codex also supports those editors through its extension, so the two can be used together. The profile also notes that some models, including GPT-5.5, retire in October, so check your model configuration after that date. Both are listed alongside GitHub Copilot and ChatGPT.
We have not run a head-to-head test of Codex against these tools, so this guide makes no claims about output quality or speed. Compare plans, supported surfaces and usage limits on each tool's own page before you choose. For the same reason, treat this guide as a description of documented features, not a verdict on which agent writes better code.
Install the Codex CLI with the install script, npm or Homebrew, as shown in the project README. Open a terminal in your repository folder, start the CLI, and sign in with your ChatGPT account or use an API key. Optionally add the IDE extension in VS Code, Cursor or Windsurf. Windsurf and Cursor appear both as alternatives and as supported editors, so choosing between them is not always an either-or decision.
Start with a small, specific task and name the files involved. Review the proposed edits, approve what you want, then run your own test suite and linter and inspect the full diff before committing. Plan details worth comparing include the free tier, which surfaces each plan lists, API availability and team features such as workspace admin. If a result looks wrong, narrow the task and try again.
OpenAI's coding agent for the CLI, IDE extension, desktop app, web and iOS, included in ChatGPT plans or billed by API.
Free stops at: Desktop app only listed, Usage limits apply
Verified developers.openai.com (opens OpenAI Codex website in a new tab)
Free · paid from $8/mo US · checked Sep 29
Yes. The ChatGPT Free plan includes Codex usage, but only in the desktop app and with usage limits. Go, Plus, Pro, Business and Enterprise/Edu plans also include Codex.
Codex has no separate subscription: it comes with ChatGPT plans, from Go at $8 per month to Plus at $20; the Pro price was not confirmed in our profile. You can also skip the plan and pay API rates with an API key.
Yes, and you pay API rates. Cloud features such as GitHub code review and Slack are not available with API-key use.
Use the install script, npm or Homebrew. The CLI is open source and runs locally on your computer.
Codex on the web and iOS is listed for the Plus plan. Availability on other plans was not confirmed.
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