Codex

1:12 Codex is OpenAI's coding agent, and as of Nov 6, 2026 it is included with every ChatGPT plan: Free ($0) and Go ($8 a month) get light use of GPT-6 Luna in the desktop app, while Plus ($20), Pro (from $100) and the business plans add Codex Cloud, GitHub code review and the stronger models. It reads a repository, plans a change, edits files, runs commands and tests, and hands back a diff or a pull request. You reach it in five places: the Codex view of the ChatGPT desktop app, the Codex CLI in a terminal, the Codex IDE Extension in VS Code and its forks (plus Codex inside Xcode and JetBrains IDEs), Codex Cloud on the web, and the ChatGPT mobile app, which drives work on a connected computer (OpenAI docs).

0:02 The name has had two lives. The first Codex, in 2021, was a model that turned English into code and powered GitHub Copilot; it was retired in March 2023. The Codex of today is an agent, first shown in May 2025, which became part of the ChatGPT desktop app on Jul 9, 2026 and shares its usage with ChatGPT Work. The history below has the dates.

Quick facts

What can Codex do?

8:49 Codex works on a real project. Given a task in plain words ("fix the failing test in the payments module", "add dark mode to the settings page"), it reads the files it needs, writes a plan, edits code, runs the project's own commands and tests to check the result, and reports what it changed. It can be steered while it works, asked for follow-ups in the same chat, and told to open a pull request when the work is ready (Codex Cloud docs).

0:51 Around that core sit the tools that make it more than a chat box: a sandbox that limits what its commands can touch, approval modes that decide when it must ask first, AGENTS.md files that carry a project's rules into every task, skills and plugins for repeatable work, Model Context Protocol (MCP) servers for outside tools, subagents for splitting up large jobs, and web search (Codex CLI docs). In the desktop app it can also use a browser and other apps on your computer (Computer Use), take Appshots of the window you are looking at, and work toward a long goal with /goal (see Codex App).

2:12 It reviews code too. Tag @codex review on a GitHub pull request and it posts a review that flags only the most serious issues; it also reviews GitLab merge requests in beta, and runs deeper security reviews on some plans (Codex Code Review, Codex Security).

Where you can use Codex

Source: OpenAI docs, Remote connections, IDE extension, read Nov 6, 2026.

The desktop app, the CLI and the IDE extension share one configuration file, ~/.codex/config.toml, and the same MCP setup, so a model or rule set once applies in all three (Models, MCP).

Is Codex free?

Yes, in a limited way. As of Nov 6, 2026 OpenAI's help center says Codex "is included across ChatGPT plans, including Free and Go" (OpenAI Help Center). Free and Go get GPT-6 Luna at Standard speed in the desktop app, "subject to rollout", with no published message numbers and no Codex Cloud (pricing). Plus at $20 a month is the first plan with cloud tasks, automatic GitHub code review and the Slack integration, and the first to offer GPT-6.1 Sol and GPT-6 Astra. The full breakdown, with message ranges per model, is on Codex Pricing and Limits; plan details are on ChatGPT Plans and Pricing.

You can also use the CLI, the IDE extension and the SDK with an OpenAI API key instead of a ChatGPT sign-in, paying API prices per token; cloud features such as GitHub review do not work that way (OpenAI API Pricing).

Codex plans at a glance

Source: OpenAI pricing docs and ChatGPT Work and Codex, read Nov 6, 2026. See ChatGPT Plus, ChatGPT Pro and ChatGPT Business.

Which models does Codex use?

Four current models are recommended in Codex as of Nov 6, 2026: GPT-6 Astra, the most capable; GPT-6.1 Sol, close to Astra at a lower cost and the default; GPT-6.1 Terra, fast, for writing, images and computer use; and GPT-6 Luna, the most efficient, for high-volume work (Models). GPT-6.1 Sol and Terra run in Codex and ChatGPT Work but not in ordinary ChatGPT chat (pricing). Reasoning effort goes from Light to Extra High, with Max for one long task and Ultra, which splits the work across subagents. The models before these, from codex-1 through GPT-5.3-Codex and GPT-5.6, are on Codex Models.

Codex history

The 2021 model. On Aug 10, 2021 OpenAI released "OpenAI Codex", a descendant of GPT-3 that translated natural language to code, in a private API beta; it was the model behind GitHub Copilot, launched with GitHub a month earlier, and was strongest in Python. OpenAI says the Codex models were deprecated in March 2023 (OpenAI, Aug 10, 2021).

0:56 The agent arrives (2025). OpenAI released the open-source Codex CLI on Apr 16, 2025 (OpenAI). On May 16, 2025 it showed a research preview of Codex as a cloud agent that could work on many tasks in parallel, powered by codex-1, a version of OpenAI o3 tuned for software engineering, first for Pro, Enterprise and Team (now Business) users; tasks typically took 1 to 30 minutes (OpenAI, May 16, 2025). Plus users got it on Jun 3, 2025; the IDE extension and code reviews came on Aug 27, 2025 (changelog). GPT-5-Codex followed on Sep 15, 2025 (OpenAI), and Codex became generally available on Oct 6, 2025 with Slack, the SDK and a GitHub Action (OpenAI).

0:00 The Codex app (2026). On Feb 2, 2026 OpenAI introduced the Codex app for macOS, "a command center for agents", and for a limited time opened Codex to Free and Go while doubling paid rate limits; the Windows version followed on Mar 4, 2026 (OpenAI, Feb 2, 2026). Plugins came on Mar 25, Appshots and Goal mode on May 21, and Codex Remote reached general availability on Jun 25, 2026 (changelog).

0:25 Into ChatGPT (Jul 9, 2026). "Codex joins the ChatGPT desktop app": from Jul 9, 2026 Codex is a view inside the ChatGPT desktop app on macOS and Windows, on every plan including Free, launched the same week as ChatGPT Work and the GPT-5.6 family (changelog, What's new). A Linux desktop preview followed on Aug 11, 2026. GPT-6 Astra reached Codex in the first week of September, GPT-6 Sol and Luna on Sep 22, GPT-6.1 Sol on Sep 29 and GPT-6.1 Terra on Oct 26, 2026 (changelog). Codex keeps its own view and its own history, separate from ChatGPT's (OpenAI Help Center).

The whole timeline of ChatGPT is on History of ChatGPT, and every product OpenAI makes is listed on OpenAI Products.

How many people use Codex?

OpenAI has published a run of weekly user counts, each on its own blog:

0:00 OpenAI's own video on Codex joining the ChatGPT app gives a higher number than its posts: the presenter opens with "more than 6 million of you use Codex every week", the latest figure OpenAI itself has given. Higher figures (7 million to 25 million) circulate on aggregator sites, but no OpenAI page or reputable report read on Nov 6, 2026 confirms them. Inside OpenAI, the company said in October 2025 that "nearly all engineers use Codex" (OpenAI, Oct 6, 2025).

How does Codex compare?

Codex competes with Anthropic's Claude Code, Cursor, GitHub Copilot and Google's Antigravity. Fair, sourced verdicts by task are on Codex vs Claude Code, Codex vs Cursor, Codex vs GitHub Copilot and Codex vs Antigravity.

What testers found

0:00 In an Aug 27, 2026 video, Tim Ruscica of Tech With Tim gave Codex and Anthropic's Claude Code the same five tasks: explaining an unfamiliar open-source codebase, building an app from scratch, refactoring a 5,000-line Python file, hunting down a planted bug and reviewing a pull request with planted bugs. He timed each one and checked the results, running GPT-5.6 Sol, then Codex's flagship, against Claude Opus 5.

20:16 On the small, well-scoped tasks he found every model correct, and said the differences were "speed and the depth of explanation, but not the correctness".

20:44 His recommendation was Codex for the fastest and most efficient tool, since it did the same work at the same correctness "much faster" and with more generous usage limits, and Claude Code where depth matters, since Opus 5 went further in every demo, writing more tests and even its own verification tool. That is one tester's run with the GPT-5.6 models, before GPT-6 reached Codex.

Frequently asked questions

What is OpenAI Codex? Codex is OpenAI's coding agent: it reads a codebase, edits files, runs commands and tests, and reviews pull requests. As of Nov 6, 2026 it runs in the ChatGPT desktop app, the Codex CLI, IDE extensions, Codex Cloud and on mobile.

Is Codex free? Yes, with limits. ChatGPT Free and Go include Codex with GPT-6 Luna in the desktop app, subject to rollout, but not Codex Cloud; Plus at $20 a month adds cloud tasks and GitHub code review.

Is Codex the same as ChatGPT? Codex is part of ChatGPT: since Jul 9, 2026 it is a separate view in the ChatGPT desktop app with its own history, and it shares usage limits and credits with ChatGPT Work.

Is Codex open source? The Codex CLI is open source on GitHub (openai/codex), as is the App Server that powers rich clients. The models it runs and Codex Cloud are not.

Does Codex need a ChatGPT subscription? No. The CLI, IDE extension and SDK also work with an OpenAI API key billed at API prices, but cloud features such as GitHub code review and Slack need a ChatGPT sign-in.

What happened to the old Codex model? The 2021 Codex model that powered GitHub Copilot was deprecated in March 2023. Today's Codex is a different product, an agent, that reuses the name.

Sources

• OpenAI docs (Codex and ChatGPT), OpenAI, read Nov 6, 2026
• Pricing, OpenAI docs, read Nov 6, 2026
• Models, OpenAI docs, read Nov 6, 2026
• Changelog, OpenAI docs, read Nov 6, 2026
• What's new, OpenAI docs, read Nov 6, 2026
• Codex CLI, OpenAI docs, read Nov 6, 2026
• Codex IDE extension, OpenAI docs, read Nov 6, 2026
• Codex Cloud, OpenAI docs, read Nov 6, 2026
• Remote connections, OpenAI docs, read Nov 6, 2026
• MCP, OpenAI docs, read Nov 6, 2026
• Using Codex with your ChatGPT plan, OpenAI Help Center, read Nov 6, 2026
• ChatGPT Work and Codex, OpenAI Help Center, read Nov 6, 2026
• OpenAI Codex, OpenAI, Aug 10, 2021
• Introducing Codex, OpenAI, May 16, 2025
• Introducing upgrades to Codex, OpenAI, Sep 15, 2025
• Codex is now generally available, OpenAI, Oct 6, 2025
• Introducing the Codex app, OpenAI, Feb 2, 2026
• Scaling AI for everyone, OpenAI, Feb 27, 2026
• Accelerating the next phase of AI, OpenAI, Mar 31, 2026
• The next phase of enterprise AI, OpenAI, Apr 8, 2026
• Codex for knowledge work, OpenAI, Jun 2, 2026
• ChatGPT is now a partner for your most ambitious work, OpenAI, Jul 9, 2026
• Introducing the Codex app, OpenAI, Feb 2, 2026 (video)
• A research preview of Codex in ChatGPT, OpenAI, May 16, 2025 (video)
• Codex just got better for developers, OpenAI, Jul 14, 2026 (video)
• Automatic code reviews with OpenAI Codex, OpenAI, Nov 4, 2025 (video)
• Codex vs Claude - an Honest Comparison, Tech With Tim, Aug 27, 2026 (video)