Codex Basics: Why You Can Say Goodbye to ChatGPT

What ChatGPT cannot do, the Codex App can; what ChatGPT can do, the Codex App does better.

As one of the most powerful AI Agent products available today, the Codex App can help you accomplish anything you want: code development, reading and writing files, deep research…

After reading this article, you will understand all the basic concepts of the Codex App, including:

1. What is the Codex App? Why is it so powerful?
2. How to download and install Codex
3. Core features of Codex explained in plain English
4. Essential Codex settings
5. Practical Codex tips

To help readers read more effectively, we will follow up with advanced tutorials to unlock the secrets of Codex step by step and ignite your curiosity about AI.

1. What is the Codex App? How is it different from ChatGPT?

The Codex App is a desktop AI Agent application launched by OpenAI. If previous AI was just a Q&A machine, the Codex App is a digital employee that can truly sit at your computer and get work done.

It has strong autonomy and can break down a goal you express in one sentence into a concrete action plan. As it executes each step in sequence, it calls on various computer functions just like a real person, until the task is complete and results are delivered to you.

Specifically, it can:

• Deeply read and write local files: Directly view, modify, and organize folders and project directories on your computer.
• Search the web for real-time information: Has a built-in full-featured browser, allowing you to search, browse, and summarize web pages from within the app without switching out.
• Control software like a human: Has visual perception capabilities, can recognize complex software interfaces in real-time, and operate various apps on your computer.
• Generate multi-dimensional work results: Automatically generate documents, images, web pages, code, and other outputs, with real-time preview support.
• Seamlessly connect to external tools: Connect directly to your Gmail, Notion, Google Drive, and other apps through plugins.
• Background automation: Set up scheduled tasks and let it automatically perform repetitive work in the background.

Compared to the familiar ChatGPT, the Codex App brings two revolutionary changes:

1. Localization: Codex App runs on your local computer and can directly read and write local files; ChatGPT is a cloud-based AI chat application—if you want it to process files, you must manually upload them.
2. Execution capability: Codex App can flawlessly execute any task, taking action directly on your computer and delivering results as needed; ChatGPT can only keep answers in the chat box—the execution step is left to you.

In summary, Codex is a super assistant that truly lives on your computer, capable of everything ChatGPT cannot do.

2. Installing the Codex App

1. Installation

Go to the Codex official website (https://developers.openai.com/codex/app) to download.

It supports Mac/Windows. Choose the appropriate installer based on your computer and download.

2. Login

Log in with your ChatGPT account. The free version comes with a small amount of credit, but we recommend starting with at least a Plus subscription.

3. Core Feature Analysis

1. Overall Interface

After entering the Codex App, the interface layout is as shown below. It mainly consists of a left navigation bar and a central workspace.

Important features in the left navigation bar include:

• Top bar: Plugins includes both plugins and skills, used to extend Codex’s capabilities. Automations is for setting up scheduled tasks.
• Middle conversation area: The Projects area is for managing project-level conversations tied to local folders. The Chats area is for temporary, standalone daily conversation history.
• Bottom settings: For global basic configuration.

The central main workspace is the core workbench—all your chats start here.

Let’s break down the core features of the Codex App so you can get started quickly.

2. Projects & Conversations

Projects and conversations are located in the left sidebar. They are two concepts you must grasp when using Codex App, representing two ways to start a session.

Projects: Correspond to a local folder. In a project session, Codex can directly read and write files within that folder. Therefore, projects are more suitable for tasks with clear goals, such as developing a website.

How to start: Click the “New Project” icon to the right of “Projects”. You can either create a new folder or select an existing folder to associate it.

It is recommended to keep the conversation structure clear, mainly including the following two points:

• Keep local folders organized, with different folders for different topics.
• Within the same project, each session should only advance one direction. For example, when developing a website, open separate sessions for different feature designs, don’t mix them together. This results in better execution and is easier to review later.

Chats (Conversations): Not tied to any local folder. More suitable for scattered Q&A and chatting needs.

How to start: Click the “New Chat” icon in the chats area as shown below.

3. Plugins and Skills

Click “Plugins” in the left sidebar to install Plugins and Skills, extending Codex’s capabilities.

Plugins are installation packages that connect Codex to external tools. For example:

• Gmail plugin: Let Codex read and manage your emails.
• Google Drive plugin: Let Codex read and edit your Docs, Sheets, and Slides.
• Vercel plugin: Let Codex directly deploy your project online.

Skills are reusable task instructions that tell Codex how to handle certain tasks. For instance, the built-in Image Gen skill lets Codex generate or edit images directly.

4. Automations

Automations let Codex automatically perform tasks in the background according to your scheduled time. Suitable for repetitive tasks that need regular execution, such as daily email summaries, regular information monitoring, stock daily reports, etc.

Setting up is simple. For example, just tell Codex in a chat:

Create an automation that checks my Gmail every morning at 9 AM and summarizes important emails into the current chat session.

5. Chat Conversation Features

1️⃣ Plan mode: First create a detailed plan before execution. Suitable for more complex tasks.

2️⃣ Permission modes: Before each conversation, you can select a permission level from the bottom-left of the input box. There are three levels:

• Default: Limited to the current workspace only. Codex will pause and ask for your confirmation when it needs to go out of bounds (access the network or files outside the workspace).
• Auto-review: Same boundary as Default, but out-of-bounds requests are automatically reviewed and decided by the AI without your manual confirmation, avoiding workflow interruptions.
• Full access: Removes all boundary restrictions. Codex can access any files and the network, executing directly without any interruptions.

For daily use, we recommend Auto-review: security is relatively controllable and won’t frequently interrupt your work progress.

3️⃣ Model and reasoning level selection: Supports different models and reasoning levels.

For daily tasks, we recommend GPT 5.5 Medium; for complex tasks, GPT 5.5 Extra High.

4️⃣ Input box shortcut symbols: In the conversation input box, there are three symbols to quickly trigger different functions.

• “@”: Allows you to reference installed plugins or specific files as context.
• “/”: Brings up a command menu. You can execute built-in commands; installed Skills also appear in this list.
• “****": Explicitly invoke a Skill. For example, typing `imagegen` directly triggers image generation.

4. Recommended Settings

Before you start using it, I recommend configuring the following four basic settings to ensure a smooth experience.

Click the settings icon at the bottom left to enter the configuration page.

1. In the permission settings, enable “Auto-review” and “Full access” so you can easily switch permission modes at any time.
2. Enable “Prevent computer from sleeping while Codex is running” so Codex’s tasks won’t be interrupted unexpectedly.
3. Configure a global instruction (Agents.md). In the custom instructions under personalization, write background information and rules you want Codex to follow long-term. Suggestions include:
   • Your identity and preferences: e.g., your daily work role, commonly used software tools.
   • Output format requirements: e.g., “Always answer in English”, “Keep the writing style concise and restrained”.
   • Principles: e.g., “Avoid over-engineering; only make necessary changes”.
4. Enable the memory function in personalization settings. Codex will automatically learn your preferences from conversations and become more attuned to you over time.

5. Super Practical Tips

1. Make good use of Plan Mode

The more complex the task, the more worthwhile it is to first open Plan Mode to confirm the plan before executing. Very suitable for:

• Tasks involving multiple file changes.
• Requirements that are not yet clear.
• Developing a function or Skill from scratch.

2. Run multiple tasks in parallel

Codex supports starting multiple tasks simultaneously, even across projects in parallel. The status of each conversation is displayed in real-time in the sidebar. When a task is completed, a blue dot appears as a reminder.

3. 4 Golden Commands

• /side: While the main thread of a project-level session is running, open a temporary side conversation for quick questions or to confirm a detail.
• /pet: Open a desktop pet on your computer screen that displays the execution status of the current task in real time, allowing you to monitor progress while doing other things.
• /status: Check your context and credit usage in the current session.
• /goal: Set a clear goal and let the agent work towards it continuously.

A good /goal prompt looks like this:

/goal Achieve , and confirm the result is valid through , while maintaining . Only use <allowed inputs, tools, file scope, or operational boundaries>. Between each iteration, Codex should choose the next step based on . If blocked, or if there are no valid paths to continue, Codex must stop and report <methods already tried, evidence obtained, current blockage, and what additional information or permissions are needed to proceed>.

4. Steer insertion mechanism

While Codex is executing a task, input a new instruction and press Steer (or Mac shortcut Cmd + Enter). The instruction is immediately inserted into the context of the current task without interrupting the ongoing work. Useful when you discover a need for a fine adjustment while the task is running.