How to Use OpenAI Codex CLI in 2026: Step-by-Step Guide
OpenAI's open-source terminal coding agent — reads, edits, and runs code directly in a local sandbox, driven by natural-language instructions.
Codex CLI is OpenAI's open-source command-line coding agent, designed to work directly in a developer's local terminal and file system rather than a hosted IDE.
Core Capabilities
Local Sandbox Execution Runs in a sandboxed environment on the developer's own machine, reading and editing files and executing shell commands (tests, builds, linters) with configurable approval levels.
Natural-Language Task Execution Developers describe a task in plain English ("add input validation to the signup form and add tests") and Codex CLI plans the changes, edits the relevant files, and runs tests to verify.
Approval Modes Ranges from fully autonomous execution to step-by-step confirmation, letting teams tune the agent's autonomy to their risk tolerance.
Git-Aware Workflow Understands the current repository's diff and history, and can prepare commits and PR descriptions summarizing its changes.
Positioning
Competes directly with Claude Code and Cursor's agent mode as a terminal-native, model-agnostic-adjacent coding agent from OpenAI.
Pricing
Free and open source; requires an OpenAI API key or ChatGPT Plus/Pro/Team account for model access.
What You'll Need
- A OpenAI Codex CLI account (free to create)
- A modern web browser or the OpenAI Codex CLI app
- Payment method for paid features
Getting Started
Create Your Account
Visit https://github.com/openai/codex and sign up for a freemium account. You'll need an email address to register. A free tier is available — you can upgrade later for more features.
Start Your First Conversation
Once logged in, you'll see the main chat interface. Type a question or task in the input box and press Enter. OpenAI Codex CLI supports coding-agent, terminal-native, code-editing, test-execution — start with a simple text prompt to get familiar.
Pro Tips
- Be specific: The more context you provide, the better the response. Instead of "write an email," try "write a professional follow-up email to a client who hasn't responded in two weeks."
- Iterate: If you don't get what you need, ask for clarification or refinement: "Make it shorter" or "Use a more formal tone."
- Use examples: Show OpenAI Codex CLI what format you want by including an example in your prompt.
- Save useful conversations: Most platforms let you name and revisit conversations — organize by project or topic.
Common Use Cases
Programming & Code
AI assistants focused on writing, debugging, and explaining code across programming languages.
Browse Programming & Code chatbots →Troubleshooting
- Responses seem generic or unhelpful
- Add more context to your prompt. Specify the audience, tone, length, and format you need. Try starting over with a clearer description of your goal.
- The tool isn't responding or is slow
- AI chatbots can experience high traffic. Refresh the page and try again. Check the service's status page if issues persist.
- Output is too long or too short
- Explicitly specify the length: "in 100 words," "as a brief summary," or "in detail with examples."
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Frequently Asked Questions
- Is OpenAI Codex CLI free to use?
- OpenAI Codex CLI has a free tier. Paid plans start from Free.
- Do I need an account to use OpenAI Codex CLI?
- Yes, you need to create an account to use OpenAI Codex CLI.
- What can I use OpenAI Codex CLI for?
- OpenAI's open-source terminal coding agent — reads, edits, and runs code directly in a local sandbox, driven by natural-language instructions.
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