Is Codex open source? The CLI is Apache 2.0, with no outside PRs

Is Codex open source? The Codex CLI is. OpenAI publishes its source code at github.com/openai/codex under the Apache License 2.0, and the LICENSE file carries the line "Copyright 2025 OpenAI". As of November 2, 2026, that covers the command-line agent. It does not mean OpenAI takes code from outside, and it does not make running Codex free.

Developers search this because Codex comes in several forms, and only one of them has a public repository to point at. The answer depends on which one you mean.

What is open source: the Codex CLI

The repository's README opens with "Codex CLI is a coding agent from OpenAI that runs locally on your computer," and ends with "This repository is licensed under the Apache-2.0 License." Apache 2.0 is a permissive license. You can use, modify and redistribute the code, including in commercial products, as long as you keep the license and copyright notices.

The README names two other ways to use Codex: the desktop app, started with codex app, and Codex Web, the cloud agent at chatgpt.com/codex. It describes both as separate options. It does not say that their source is in this repository, so we don't claim they are open source. The CLI is the part OpenAI's license statement covers.

The repo's NOTICE file also credits code derived from Ratatui, a terminal interface library under the MIT license, which is normal for a project this size.

What you can do with the code

The install guide in the repository tells you how to build from source. You clone the repo, go to the codex-rs folder, which is a Cargo workspace (Rust's build system), and build from there. The guide lists macOS 12 or newer, Ubuntu 20.04 or newer, Debian 10 or newer, and Windows 11 through WSL2 as the supported systems.

Most people skip that and install a prebuilt copy. The README lists these routes:

What open source does not mean here

Two limits are worth knowing before you plan around it.

First, OpenAI does not accept outside code. Its contributing guide says "We do not accept external code contributions or pull requests." It asks the community for bug reports, root-cause analysis and feature requests through the issue tracker, and says the Codex team makes the code changes. You can fork and change your own copy under the license. You cannot send those changes back.

Second, the license is on the code, not on the service behind it. The README says to run codex and choose "Sign in with ChatGPT" to use it with a Plus, Pro, Business, Edu or Enterprise plan, or to use an API key with extra setup. Either way you pay OpenAI or use a plan that includes it. Our article on whether Codex is free covers the plans and API billing as of October 28, 2026.

Is Codex open source like Claude Code?

No. Anthropic's Claude Code is proprietary software, as we explain in Is Claude Code open source?. Codex CLI is the opposite case: the agent's own code is public under a standard license. Neither article says anything about the models behind the tools, which are a separate question.

The open source fund

OpenAI's repository also contains a Codex open source fund page. It describes a $1 million initiative for open source projects that use Codex CLI and other OpenAI models, with grants of up to $25,000 in API credits, reviewed on a rolling basis. That is a grant program for other projects. It is separate from Codex's own license.

The OpenAI docs for the CLI, which now live at learn.chatgpt.com, cover installation and sign-in but do not describe the license. For licensing, the repository's LICENSE file is the source to check.