ChatGPT (Codex) Tutorial

Codex is a cloud-based software engineering AI agent developed by OpenAI.

Codex can independently understand, write, debug, and review code, and can handle multiple development tasks in parallel.

The official description of Codex is:One agent for everywhere you code。

Codex is like an engineer who can independently complete development tasks.

After July 10, 2026, Codex merged into ChatGPT, and Codex became an application of ChatGPT.

Who should read this tutorial?

  • Have learned at least one programming language (e.g., JavaScript / Python / Java / Go)
  • Can understand basic syntax, functions, conditionals, and loops
  • Have written simple projects or practice code
  • Want to use AI to improve development efficiency and engineering capabilities
  • Independent developers or engineers who need to maintain projects long-term
  • Technical leads or core team members

Required basic skills

  • Basic programming ability (can read and write simple code)
  • Basic code reading and comprehension ability
  • Can use common development tools (editor, command line)
  • Willing to understand code rather than rely entirely on AI

Usage methods

Codex provides four usage methods to meet the needs of different scenarios:

MethodDescriptionApplicable scenarios
App (Desktop application)macOS/Windows desktop clientFull features, multi-project parallelism
IDE extensionVS Code, Cursor, Windsurf pluginsDeeply integrated development environment
CLI (Command line)Terminal interactive toolTerminal enthusiasts, script automation
Web (Cloud)chatgpt.com/codex web versionRemote access, parallel tasks

Five core capabilities

CapabilityDescription
Write codeDescribe the feature you want to build; Codex generates code matching your intent and automatically adapts to project structure and conventions.
Understand codebaseRead and explain complex or legacy code to help you quickly familiarize yourself with unfamiliar projects.
Code reviewAnalyze code to identify potential bugs, logic errors, and unhandled edge cases.
Debugging and fixingTrace failures, diagnose root causes, and provide targeted fixes.
Automate tasksExecute repetitive workflows: refactoring, testing, migration, project setup, etc.

Differences from traditional AI programming tools

Comparison dimensionCodexChatGPT
Working modeActive execution loop (model + actions)Single-turn conversation response
File operationsCan read, create, and modify project filesOnly provides suggestions, does not operate on files
Command executionCan run shell commands in a sandboxDoes not execute commands
Project understandingDeeply understands the entire codebase structureBased only on conversation context
Task completionAutomatically executes until completionRequires manual copy-paste

Available plans

Codex is included in the following ChatGPT plans:

PlanPriceCodex features
FreeFreeExplore Codex for quick coding tasks
Plus$20/monthWeb, CLI, IDE, cloud integration, mainstream models
Pro$200/month10x-20x higher limits, prioritized processing, Spark model
BusinessPay-as-you-goLarger VMs, SAML SSO, MFA
EnterpriseContact salesSCIM, EKM, RBAC, audit logs, data residency

Related resources

Related products

Domestic Alibaba and ByteDance also have AI IDEs developed based on VS Code:

Online AI application generation and development platform:

Other extensions