GitHub Copilot works inside editors such as VS Code and JetBrains and also offers a coding agent and a command-line tool. OpenAI Codex is OpenAI's coding agent, available as a command-line tool, an IDE extension and a cloud service. Both have grown beyond simple autocomplete, so the overlap is real.
The short version
| GitHub Copilot | OpenAI Codex | |
|---|---|---|
| What it is | AI assistant for editors, plus an agent and CLI | Coding agent: CLI, IDE extension and cloud |
| Starting point | Your editor (VS Code, JetBrains and others) | Terminal-first, with IDE and cloud options |
| Free plan | Yes (limited completions, chat and agent use) | Unclear. OpenAI lists a Free ChatGPT plan for trying Codex, but check what it includes. Full use needs a paid plan or API credits |
| Open source | No | Yes |
| MCP support | Yes | Yes |
| Project instructions | Check GitHub's docs | AGENTS.md |
| GitHub tie-in | Native: issues and pull requests | A GitHub integration is listed in OpenAI's docs |
Plans change often. See GitHub's plans and OpenAI's Codex site.
What they have in common
- More than autocomplete. Each offers an agent that can take on a larger task.
- Several surfaces. Copilot spans editors, a CLI, the web and more. Codex spans a CLI, IDE extension and cloud.
- MCP support. Both can connect to MCP servers (a standard way to plug extra tools into an AI).
- Paid tiers for heavy use. Check each vendor's page for how limits work.
Key differences
Entry point. Copilot starts in your editor. GitHub lists support for VS Code, Visual Studio, JetBrains IDEs, Xcode, Vim, Neovim, Zed and Eclipse, so you probably don't have to change tools. Codex is terminal-first, like Claude Code, though it has an IDE extension too. Its CLI installs with npm install -g @openai/codex.
Cost to try. Copilot has a Free plan (GitHub lists 2,000 completions a month and limited chat and agent use). OpenAI lists a Free ChatGPT plan for exploring Codex, but it isn't clear what it includes, so check before relying on it. For regular use, OpenAI points to a paid ChatGPT plan (such as Plus, Pro, Business, Edu or Enterprise), and you can also use an API key.
GitHub workflow. GitHub describes changes that start as an issue, get picked up by an agent and return as a pull request. If your team runs on GitHub, that is the obvious home for Copilot. Codex also lists a GitHub integration, but check OpenAI's docs for what it covers.
Openness. Codex is open source; Copilot is not. That may matter if you want to inspect or adapt the tool.
Editor differences. Copilot's available features differ from one editor to another, so confirm yours supports what you need.
Do they work together?
They can coexist. GitHub's Copilot plans page lists third-party coding agents (such as Claude and OpenAI Codex) under Copilot in the cloud on Pro+ and Max, not on Pro. Otherwise, there is nothing stopping you from using Copilot's editor suggestions alongside Codex for bigger tasks.
Who should pick what
- You want to try AI coding for free: GitHub Copilot.
- You use several editors, or JetBrains: GitHub Copilot.
- Your workflow centres on GitHub issues and pull requests: GitHub Copilot.
- You prefer a terminal agent and want an open-source tool: Codex.
- You already pay for ChatGPT: Codex fits neatly.
Our verdict
Both are credible. Copilot wins on ease of starting; Codex wins if you like terminal-first agents and the OpenAI ecosystem. Run one real task through each before committing.