OpenAI Codex Freemium

What it is

Codex is OpenAI's coding agent. It comes in several forms: an open-source CLI (Apache-2.0) that runs locally in your terminal, IDE extensions for VS Code, Cursor and Windsurf, a desktop app launched with codex app, and Codex Web at chatgpt.com/codex, where tasks run in cloud sandboxes and can end in a pull request. You sign in with a ChatGPT account, so access comes with a plan many people already pay for.

The README gives a one-line installer for macOS and Linux (curl -fsSL https://chatgpt.com/codex/install.sh | sh), a PowerShell installer for Windows, and alternatives through npm (npm install -g @openai/codex) and Homebrew (brew install --cask codex).

Key features

• Local agent in the terminal that reads, edits and runs code inside a sandbox
• Cloud tasks that run in parallel and produce reviewable diffs and pull requests
• IDE extension so the same agent works next to your editor
• API key mode for automation and CI, billed at API rates instead of plan limits

Skills, subagents and MCP

Codex reads AGENTS.md for project instructions. MCP servers are configured in ~/.codex/config.toml (or a project-level .codex/config.toml for trusted projects) and can be added from the command line, for example codex mcp add <name> -- <command>. Agent Skills follow the open SKILL.md format: Codex looks for them in .agents/skills in the repository, ~/.agents/skills for the user, and an admin location, and you can call one explicitly with $skill-name or let Codex pick it automatically. Skills can also declare MCP server dependencies. The documentation includes a page on configuring subagents.

Pricing

At the time of writing (September 2026), OpenAI lists Codex on every ChatGPT plan: Free ($0), Go ($8/month), Plus ($20/month), Pro (from $100/month, with 5x or 20x Plus limits), and Business ($20 per user per month billed annually, $25 monthly). Edu and Enterprise are priced through sales. Usage allowances are shared with the rest of ChatGPT, and an API key option bills by token.

Who it is for

ChatGPT subscribers who want an agent without another bill, and teams that like to hand off tasks to cloud sandboxes and review the resulting pull requests.

Verdict

Codex is a strong, open-source-at-the-core agent with standard AGENTS.md, MCP and skills support. It has fewer ways to package and share extensions than Claude Code, and how far you get depends on your ChatGPT plan's limits.