Introduction
Codex, a programming support AI agent announced by OpenAI in May 2025 , is dramatically changing the way developers and education work. Codex is a next-generation AI that can understand instructions in natural human language and automatically generate corresponding program code. It is also used as the core of GitHub Copilot.
However, the code generated by Codex is not always optimal, and when developing code that requires complex business requirements or security, it is essential that developers themselves review and test the code rather than relying too heavily on AI output.
This article will introduce the basic structure and features of Codex, as well as tips on how to use it, and also introduce examples of its use in actual business and learning situations. It will be useful not only for engineers but also for business people who want to improve work efficiency with no-code.
What is Codex?
Codex is a natural language processing-based AI model developed by OpenAI that can understand human language and automatically generate accurate programming code from it. It is tuned based on GPT-3 and supports a variety of programming languages, including JavaScript, Python, Ruby, Go, Shell, and HTML.
It is particularly known for being included in “GitHub Copilot,” which is integrated with GitHub, and when engineers give instructions in natural language, such as writing comments, it suggests and generates code accordingly.
The greatest feature of Codex is that even people with little programming expertise can easily work with code in natural language. There’s no need to memorize complex grammar, and it’s used to improve work efficiency, speed up prototyping, and for educational purposes. In recent years, it’s also being used for the initial design of web app development and to automate repetitive tasks, revolutionizing the development field.
Codex Performance
OpenAI Codex is an innovative AI model that can understand natural language and generate code. It offers flexible programming support that was difficult with conventional AI, and is equipped with advanced functions that meet a variety of development needs.
Here we will explain in detail the five main features of Codex, with concrete examples.
Multilingual support (supports multiple programming languages)
Codex supports over a dozen major programming languages, including Python, and allows for flexible code generation. Supported languages include JavaScript, Java, C++, Go, Ruby, PHP, Shell, and TypeScript, and it understands and outputs the optimal syntax and grammar for each language.
It is particularly well-suited to Python, achieving highly accurate results when creating scripts for web scraping and machine learning. It also supports markup languages such as HTML and CSS, making it a powerful tool for assisting with web development and UI design.
It also supports certain frameworks (React, Flask, Django, etc.) to some extent, greatly expanding the scope of development.
Generate code from natural language
One of Codex’s most notable features is its ability to convert natural language into code. For example, you can give instructions in Japanese, such as “Create a program that responds to user input with a greeting,” and it will automatically generate the appropriate code.
This prompt-based development support provides an intuitive experience that even beginners can use to implement. Even for somewhat complex processes such as “retrieving data from an API and saving it in CSV,” Codex structures and translates it into code by providing step-by-step instructions in natural language.
The great appeal of Codex is that its natural language processing capabilities allow specification-level language to be used directly in development.
Completion and refactoring are also possible
Codex also supports code completion and refactoring (organization and optimization), making it more practical than a simple code generation AI. The ability to predict the next step in a piece of code written by the developer and automatically complete it is particularly useful in an IDE environment.
Codex can also suggest ways to improve redundant code written by beginners or processes with complex structures to make them more efficient and easier to read. For example, it can simplify deeply nested if statements or repetitive syntax, or turn duplicated processes into functions, automatically taking into consideration the “readability” and “maintainability” required in practice.
This increases the speed of development while maintaining quality.
Implemented on GitHub Copilot
A typical implementation of Codex is “GitHub Copilot,” provided by GitHub and Microsoft. Copilot is a plugin that can be integrated into development environments such as Visual Studio Code (VS Code) to utilize the power of Codex in real time. When a user starts writing code, Copilot predicts and suggests the next line of code, and automatically generates entire functions based on comments.
Codex is used as the engine, resulting in high accuracy and dramatically improving development speed and productivity. Commands written in English, in particular, tend to produce highly accurate responses, and repetitive processing and template work can be completed in just a few lines.
Supports error detection and debugging
Codex not only generates code, but can also be used to detect errors and assist with debugging. It can detect grammatical and logical errors in written code and suggest improvements. For example, if you paste a code that has a “SyntaxError” and ask “Why is this error occurring?”, Codex will identify the error, explain the reason, and suggest a fix.
In addition to correcting errors, another advantage is that it will respond to requests such as “Can this code be written more concisely?” and suggest better designs. It functions as a learning guide for beginners and a development efficiency tool for advanced users.
Codex features and what you can do
OpenAI Codex is not just a code generation AI, but a multi-functional AI agent that supports every phase of development work .
In addition to creating code from natural language, Codex also has a variety of features that greatly improve developer productivity, such as completion, refactoring, error correction, API integration, etc. Below, we will introduce five major things that Codex can do.
Generate source code from natural language
The biggest feature of Codex is that it can automatically generate source code from natural language instructions. For example, just enter “Write Python code to display the current date,” and the corresponding code will be displayed instantly.
Moreover, it supports not only English but also some Japanese, making it easy to use for beginners and non-engineers. Even for somewhat complex tasks such as “web scraping code” and “saving data in JSON format,” step-by-step prompts help you get closer to the desired code.
Since text can be treated as commands, development methods that generate code directly from specifications become practical.
Code completion and prediction
Codex also has a feature that understands the flow of code written by the user and completes and suggests the next code to write in real time. This is more advanced than “autocomplete” and can predict the entire logic after deeply analyzing the context.
For example, when you start a for loop, the system will automatically suggest the end condition and the processing within the loop. It also takes into account the usage of existing functions and libraries, significantly speeding up development. In integrated environments such as GitHub Copilot, it can be used naturally as a development aid, and is particularly effective in avoiding syntax construction mistakes that beginners often encounter.
Code refactoring and optimization
Codex also supports refactoring (organization and improvement) and optimization of existing code. For example, in response to a prompt such as “Make this code more concise,” Codex will return suggestions such as grouping duplicated processes into functions and improving deeply nested structures.
We may also suggest improvements that take into consideration processing speed and memory usage, enabling high-quality optimization in terms of not only readability but also execution efficiency.
It also serves as an excellent learning tool for coding, as it rewrites redundant code written by beginners into a format that conforms to “best practices.” It is also attracting attention in team development as it reduces the effort required for code reviews.
Error detection and correction suggestions
Codex has a feature that detects errors in written code and clearly explains the cause and how to fix them. For example, just by asking “Why is this code causing an error?”, it will point out syntax mistakes, undefined variables, incorrect indentation, etc., and even suggest improvements such as “This is the correct way to write it.”
This feature can save a lot of time, especially in development, where debugging can often take up a lot of time. Error explanations are also output in a format that’s easy for people to understand, making it easy for even beginners to understand the cause and facilitating learning. It’s also capable of handling errors that span multiple lines and logical mistakes, making it a useful support feature even at the practical level.
API integration and data processing script creation
Codex is also good at creating scripts for calling APIs and processing data. For example, if you tell it to “write code to get the latest tweets from the Twitter API and save them as a CSV file,” it will output code that covers everything from importing the necessary libraries to authenticating, retrieving data, and writing to a file.
It also supports common API formats such as REST API and GraphQL, making it possible to automate server-to-server communication processes and web application development. It can also generate processes such as reading and writing Excel files, and data normalization and filtering using natural language instructions. Its practicality in business automation and data analysis makes it a powerful tool for use in business situations.
Codex Pricing
As of May 17, 2025, OpenAI’s Codex is provided through ChatGPT and requires a paid plan. In addition to the existing GitHub Copilot and API offerings, the Codex-based code completion feature is now available with the following ChatGPT plans:
In particular, ChatGPT Team and Enterprise plans are well-suited for collaborative development and team management, making them suitable for corporate use. In the future, ChatGPT Plus and the Edu plan for educational institutions will also be available.
| Plan Name | subject | Price (tax included) | Key Features |
| ChatGPT Pro | Individual users | $20/month | GPT-4 (including Codex) enabled, fast response, priority access |
| ChatGPT Team | Small Team | $25/user/month | Team management, shared workspace, and enhanced security |
| ChatGPT Enterprise | For businesses | Please inquire | SSO support, large team management, unlimited token usage, etc. |
| ChatGPT Plus (planned) | General users | to be decided | Planned to support new features including Codex |
| ChatGPT Edu (planned) | For educational institutions and students | to be decided | Plans are underway to implement Codex and AI learning support features for educational settings |
Codex is a tool that can meet a wide range of development needs, from beginners to advanced developers, through code generation from natural language. In particular, it can be easily used through ChatGPT’s interface, making it more flexible to implement and use than ever before.
If you are considering serious business use, we recommend the Business plan, which includes team operations and security management features.
How to use the Codex
Codex used to be primarily available through GitHub Copilot, but now it’s been integrated into ChatGPT, making it easier for more users to use. Here we’ll explain how to use Codex via ChatGPT and GitHub Copilot.
How to use Codex from ChatGPT
As of 2025, Codex’s features are available in paid plans such as ChatGPT Pro, Team, and Enterprise, and its use is spreading not only among engineers but also among general business people. It is very intuitive to use.
After logging in to ChatGPT, select GPT-4 (which supports code generation) and simply enter natural language input into the prompt, such as “Create a login authentication function in Python” or “Write form validation in JavaScript,” and the Codex will output the corresponding code. ChatGPT can also handle code corrections, error checks, and conversion to other languages, all directly. This significantly lowers the barrier to entry for programming. Because it runs on a browser, no environment setup is required.
How to use Codex from GitHub Copilot
You can still use Codex as GitHub Copilot as before. First, create a GitHub account and sign up for a personal or business plan from the official GitHub Copilot page. After signing up, install the GitHub Copilot extension in Visual Studio Code (VS Code) or a JetBrains editor and log in with your GitHub account. That’s it, setup is complete.
When using it, you write comments in natural language in the editor, and Codex will automatically suggest and complete code based on the content. It also supports automating repetitive processes and refactoring existing code, contributing to improving development efficiency in particular.
How to use Codex via API
For greater flexibility, you can incorporate OpenAI into your own apps and services using the OpenAI Codex API. Obtain an API key from the OpenAI official website and send requests using the Python or Node.js SDK.
Prompt-based code generation allows for highly customizable development, making it particularly suitable for experienced engineers and system developers, helping them build automated tools and streamline data processing workflows.
3 Use Cases of Codex
OpenAI’s Codex is being increasingly adopted in actual business settings due to its high level of programming support. Here, we will introduce three representative companies that use Codex: Cisco, Superhuman, and Kodiak, and explain in detail how AI is helping them in their respective fields.
Cisco
Cisco, a global leader in network equipment and security solutions, has been an early adopter of AI technology. Cisco’s Data Center Network Manager (DCNM) is using Codex to enhance some of its automation functions and security check processes.
Codex’s natural language processing capabilities are being used to automatically code security configuration templates written by engineers, compare them with existing configurations, and point out inconsistencies and risks. This is expected to improve the efficiency of network management and reduce human error, and is attracting attention as a new standard for AI-assisted infrastructure operations.
Reference: The Future is Coming Faster than You Think
Superhuman
Superhuman, known as the “world’s fastest email app,” is a SaaS company that has attracted attention for its thorough UX design and adoption of cutting-edge technology. Using Codex, the company implemented features such as automatic response generation based on user input in natural language, template optimization, and command completion.
For example, simply typing “Let’s meet next Tuesday” generates a thoughtful email proposal with suggested dates and locations, significantly reducing the time it takes to compose an email. Codex also predicts your intent and suggests optimal expressions as you type, providing an intuitive experience that keeps up with the speed of your thoughts.
Through these efforts, Superhuman is using Codex not just as a development support tool, but as a fundamental technology that supports the user experience.
See also: Anatomy of Superhuman’s Incredible Customer Acquisition (2/3)
Kodiak
Kodiak Robotics is a US startup developing self-driving trucks, focusing on technological innovation in the logistics industry. The company uses Codex to manage complex code bases, including the development of autonomous driving algorithms, sensor control, and routing logic. Codex automatically generates code from specifications and requirements written by engineers in natural language, refactors existing code, generates comments, and suggests bug fixes, enabling the company to achieve both development speed and quality.
It has proven particularly effective in integrating modules written in multiple languages and automatically generating code for connecting to external APIs. AI-based development support has become an essential element in bringing cutting-edge technologies to market in a short space of time, and Kodiak’s use of Codex has further increased its competitive advantage.
Reference: Leading the way in truck automation with cutting-edge AI technology
summary
Codex is an AI agent specialized in programming support , offering a variety of functions such as coding automation, error correction, refactoring, etc. In particular, its ability to generate code from natural language enables non-engineers to get involved in development, bringing innovation to the development workplace.
However, not all code generated by Codex is completely accurate or safe, and developers themselves must review and test the code, especially when developing code with high security requirements or implementing complex algorithms. To maximize the convenience of AI, it is essential to use it in conjunction with “human eyes.”
With the use of AI expected to expand to even more industries and projects in the future, HBLAB offers support for the introduction of cutting-edge AI technology and consultations on business automation. If you are a company considering AI-based development or PoC implementation, please contact HBLAB. We will propose the optimal solution tailored to your challenges.
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Codex FAQ
1. What are the future prospects for Codex?
Since its release, Codex has been well received by many developers and has expanded the possibilities of AI-assisted programming. Looking ahead, we expect to see further integration with more development environments and IDEs, as well as enhanced code quality and security check functions.
In particular, it is expected to enable more comprehensive support, such as real-time bug detection, automatic suggestions for appropriate library dependencies, and overall project design assistance.
In addition to improving the performance of Codex, OpenAI is also developing APIs and enterprise features aimed at corporate use as well as individual developers, which will further accelerate adoption in team development and large-scale projects.
2.What future does “Codex” pave for AI programming?
Codex revolutionizes the traditional programming process by generating sophisticated programming code from natural language.
For example, even novice developers can easily implement complex processes with the help of AI, lowering the learning barrier. Even for experienced engineers, AI is expected to improve work efficiency in many ways, including reducing routine work, enabling rapid prototyping, and supporting implementation across multiple languages.
Furthermore, by linking with the no-code/low-code movement, it is possible that the work efficiency of non-engineers will also improve, potentially furthering the democratization of software development as a whole. Codex can be said to symbolize the future of development through “co-creation between AI and humans.”
3. What should I be careful of when using Codex?
Codex is a very useful tool, but there are a few things to keep in mind when using it. First, the accuracy and security of the generated code should always be verified.
Even if the code generated by AI appears accurate at first glance, it may contain unexpected behavior or security holes, so review is essential, especially when using it in a production environment. Copyright issues also need to be taken into consideration. Codex learns from code on the Internet, and in some cases, it may output code similar to that of others.
Therefore, you must also check whether the generated code violates any license. Furthermore, when using APIs, you should also be mindful of costs, rate limits, and data privacy. You can maximize the benefits of Codex by using it appropriately and with an understanding of its uses.
