ChatGPT (Codex) Tutorial

Codex is OpenAI's cloud-based software engineering agent (AI Agent).

Codex can autonomously 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 was merged into ChatGPT, and Codex became an application of ChatGPT.

Who should read this tutorial?

  • Have learned at least one programming language (such as JavaScript / Python / Java / Go)
  • Can understand basic syntax, functions, conditional statements, and loops
  • Written simple projects or practice code
  • Want to leverage AI to improve development efficiency and engineering capabilities
  • Independent developers or engineers who need long-term project maintenance
  • Technical lead or core team member

Basic capabilities required

  • Basic programming skills (able to read and write simple code)
  • Basic code reading and comprehension ability
  • Familiar with common development tools (editors, command line)
  • Willing to understand code rather than completely relying on AI

Usage

Codex offers four usage modes to meet different scenario needs:

MethodDescriptionApplicable scenarios
App (desktop application)macOS/Windows desktop clientFull functionality, parallel multi-project
IDE ExtensionsVS Code, Cursor, Windsurf PluginsDeeply integrated development environment
CLI (Command Line)Interactive terminal toolTerminal enthusiasts, script automation
Web (Cloud)chatgpt.com/codex Web VersionRemote access, parallel tasks

Five core capabilities

SkillsDescription
Write CodeDescribe the feature you want to build, and Codex generates code matching your intent, automatically adapting to the project structure and conventions
Understand CodebaseRead and explain complex or legacy code, helping you quickly become familiar with unfamiliar projects
Code ReviewAnalyze code to identify potential bugs, logic errors, and unhandled edge cases
Debug and FixTrace failures, diagnose root causes, and provide targeted fixes
Automate TasksExecute repetitive workflows: refactoring, testing, migration, project setup, etc.

Differences from traditional AI coding tools

Comparison DimensionCodexChatGPT
Work ModeProactively execute loops (model + actions)Single-turn response
File OperationsCan read, create, and modify project filesOnly provides suggestions, does not operate on files
Command ExecutionCan run Shell commands in a sandboxDo Not Execute Commands
Project UnderstandingDeep understanding of the entire codebase structureBased only on conversation context
Task CompletionAutomatically executes until completionRequires manual copy-paste

Applicable Plans

Codex is included in the following ChatGPT plans:

PlanPricingCodex Features
FreeFreeExplore Codex for fast coding tasks
Plus$20/monthWeb, CLI, IDE, cloud integration, mainstream models
Pro$200/month10x-20x higher limits, priority processing, Spark model
BusinessPay-as-you-goLarger VM, SAML SSO, MFA
EnterpriseContact SalesSCIM, EKM, RBAC, audit logs, data residency

Related resources

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Online AI application generation and development platform:

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