How to Use Codex on Your Phone via the ChatGPT App

Introduction

OpenAI has finally extended its powerful coding assistant, Codex, to mobile devices. Previously confined to desktop browsers, a command-line interface (CLI), or the web version, Codex now integrates directly into the ChatGPT app on both iOS and Android. This means you can tap into your desktop environment, issue commands, review files, and even code on the go—all while staying perfectly synced with your primary machine. In this step-by-step guide, we’ll walk you through everything you need to get started, from the required software to the actual connection process, and share tips to make the most of this new mobile capability.

How to Use Codex on Your Phone via the ChatGPT App — Source: thenewstack.io

What You Need

A compatible mobile device running iOS or Android (with the latest version of the ChatGPT app installed).
Codex desktop app (the macOS version is required; Windows support is coming soon). You can download it from your OpenAI account or the Codex website.
A running desktop machine (laptop, Mac Mini, or any other Mac where Codex is installed and active). This machine will host your working environment.
A stable internet connection on both your phone and the desktop machine. For best performance, use Wi-Fi.
An OpenAI account with access to Codex (free or paid plans, including the Go tier).
Optional: Remote SSH configuration if you plan to connect to enterprise remote environments. This requires SSH credentials and network access.

Step-by-Step Instructions

Step 1: Update Your Apps

Before you can use Codex on mobile, both the ChatGPT app and the Codex desktop app must be up to date. Go to your phone’s app store (Apple App Store or Google Play Store) and check for any pending updates for ChatGPT. On your Mac, open the Codex app and navigate to its settings (or check your menu bar icon) to ensure you’re running the latest version. Without the latest updates, the mobile connection feature won’t appear.

Step 2: Launch Codex on Your Desktop

Open the Codex application on your Mac. Log in with your OpenAI credentials if prompted. You’ll see your usual desktop workspace—this is the environment your phone will mirror. Keep this app running in the background; do not close it. Codex will listen for connections from your mobile device.

Step 3: Sign Into ChatGPT Mobile

Launch the ChatGPT app on your smartphone. Ensure you are logged into the same OpenAI account that you use for Codex. The app will now include a new Codex-related option in its interface. Look for an icon or menu item labeled “Codex” or “Connect to Desktop” (the exact naming may vary as the feature rolls out). Tap on it to proceed.

Step 4: Establish the Connection

The ChatGPT mobile app will automatically scan for your desktop machine if both devices are on the same local network. If it doesn’t find it, you may see an option to enter a pairing code or manually specify your desktop’s IP address. For a secure connection, OpenAI uses a relay layer that keeps your machine reachable without exposing it to the public internet. Once the connection is established, you’ll see a confirmation on both devices.

Step 5: Verify the Sync

Your phone now displays the live state of your desktop environment. This includes open files, running processes, and any ongoing Codex sessions. To test the sync, try typing a simple command on your phone—for example, ask Codex to “list all files in the current directory” or “open a specific project.” You should see the same response you’d get on your desktop. The connection is persistent, so any changes you make on one device appear on the other in real time.

Step 6: Work Across Threads

One of the key advantages of this mobile integration is that it supports all your existing Codex threads. Unlike similar tools (such as Anthropic’s Dispatch, which runs tasks on separate threads), your mobile session inherits every conversation and context you’ve started on your desktop. You can continue a complex debugging session, switch between projects, or pick up a code review—all from your phone. Just type or speak your request, and Codex will execute it on your desktop machine remotely.

Step 7: Connect to Remote Environments (Optional)

If you work in an enterprise setting with remote servers, Codex on mobile also supports SSH connections. To set this up, first configure the SSH access on your desktop Codex app (under Settings > Remote Environments). You’ll need the host, port, and credentials. Once configured, you can select that remote environment from your phone when connecting. This allows you to manage code on cloud instances or private corporate networks without being physically present.

Tips for a Smooth Experience

Keep both apps updated. OpenAI is rolling out new features frequently; staying current ensures you have the best performance and security.
Use a strong Wi-Fi connection. While cellular data works, large file transfers or real-time syncing are more reliable over Wi-Fi.
Remember the macOS limitation. As of now, the Codex desktop app only connects to mobile via macOS. Windows support is coming soon—until then, Windows users cannot use this mobile feature.
Leverage the relay security. OpenAI’s relay layer protects your desktop from direct internet exposure. Avoid disabling it unless you fully understand the risks.
Explore the free tier first. The mobile connection works even on free and Go plans, so you can test it before committing to a higher subscription.
Compare with other tools. Though similar to Anthropic’s Dispatch for Claude Cowork, OpenAI’s implementation lets you work across all threads, making it more versatile for continuous workflows.
Use voice commands. The ChatGPT app supports voice input. You can dictate coding instructions hands-free—ideal for quick fixes while away from your desk.
Monitor battery life. Running a constant connection may drain both your phone and laptop batteries. Keep your devices charged or plug them in during extended sessions.