Gemini CLI vs OpenAI Codex
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
AI tool · Open source
Google's open-source terminal agent that uses Gemini models to read code, edit files and run commands.
AI tool · Paid
OpenAI's coding agent that works in the cloud, a CLI and IDE extensions to write features, fix bugs and open pull requests.
Our verdict
Gemini CLI is a free, open-source terminal agent built on Google's Gemini models, with a large context window that suits questions about big codebases. OpenAI Codex is a paid coding agent that runs tasks in the cloud, with a CLI and IDE extensions, and is aimed at handing off well-scoped work such as features, bug fixes and pull requests. Choose based on whether you want a free local terminal tool or a paid agent you can delegate tasks to.
Pick Gemini CLI if you want a free terminal coding agent and need to ask questions across a large codebase.
Pick OpenAI Codex if you want to delegate well-scoped coding tasks to a cloud agent and open pull requests from them, and you're willing to pay.
| Key difference | Gemini CLI | OpenAI Codex |
|---|---|---|
| Price | Open source with generous free usage; free tier via Google account | Paid product; requires a paid plan |
| Where it runs | Terminal (CLI) on macOS, Windows and Linux | Cloud tasks on the web, plus CLI, VS Code, macOS and Linux |
| Best at | Large-context questions and free terminal coding help | Delegating scoped tasks in parallel and handling GitHub pull requests |
| Integrations | Works with VS Code and GitHub; supports MCP | Works with GitHub and VS Code; GitHub PR and review support |
| Caveat | Behaviour can be less predictable; review its changes | Review every pull request; large refactors need guidance |
Written with AI from both products' catalogue entries · updated 2026-10-29
Who each one is for
Choose Gemini CLI if you need…
- Free terminal coding agent
- Large-context codebase questions
Choose OpenAI Codex if you need…
- Delegating tasks to a cloud agent
- ChatGPT subscribers who code
Side-by-side
| Gemini CLI | OpenAI Codex | |
|---|---|---|
| Type | Coding · Coding agents | Coding · Coding agents |
| Price | Open source | Paid |
| Platforms | CLI, macOS, Windows, Linux | Web, CLI, VS Code, macOS, Linux |
| Works with | VS Code, GitHub | GitHub, VS Code |
| Hands-on tested by us | Not yet | Not yet |
| Last checked | 2026-10-29 | 2026-10-29 |
What each one is
Gemini CLI
Google's open-source terminal agent that uses Gemini models to read code, edit files and run commands. Generous free usage. Behaviour can be less predictable than mature agents; review changes.
OpenAI Codex
OpenAI's coding agent that works in the cloud, a CLI and IDE extensions to write features, fix bugs and open pull requests. Strong for well-scoped tasks. Review every pull request it opens; large refactors still need guidance.
Best for
Gemini CLI
- Free terminal coding agent
- Large-context codebase questions
OpenAI Codex
- Delegating tasks to a cloud agent
- ChatGPT subscribers who code
Strengths
Gemini CLI
- Terminal agent
- Large context window
- MCP support
- Free tier with a Google account
OpenAI Codex
- Cloud tasks with parallel runs
- Open-source CLI
- IDE extension
- GitHub pull requests and reviews
Frequently asked questions
Should I use Gemini CLI or OpenAI Codex?
Gemini CLI is a free, open-source terminal agent built on Google's Gemini models, with a large context window that suits questions about big codebases. OpenAI Codex is a paid coding agent that runs tasks in the cloud, with a CLI and IDE extensions, and is aimed at handing off well-scoped work such as features, bug fixes and pull requests. Choose based on whether you want a free local terminal tool or a paid agent you can delegate tasks to. Pick Gemini CLI if you want a free terminal coding agent and need to ask questions across a large codebase. Pick OpenAI Codex if you want to delegate well-scoped coding tasks to a cloud agent and open pull requests from them, and you're willing to pay.
What is the difference between Gemini CLI and OpenAI Codex?
Gemini CLI: Google's open-source terminal agent that uses Gemini models to read code, edit files and run commands. OpenAI Codex: OpenAI's coding agent that works in the cloud, a CLI and IDE extensions to write features, fix bugs and open pull requests. Gemini CLI suits free terminal coding agent, while OpenAI Codex suits delegating tasks to a cloud agent.
Are Gemini CLI and OpenAI Codex free?
Gemini CLI: Open source. OpenAI Codex: Paid.
What are other alternatives to Gemini CLI and OpenAI Codex?
Other options people compare them with include Claude Code, Amp, Aider, Cline, Devin.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.