GitHub Copilot helps modernize Java and .NET apps, easily updating legacy code with AI
Hi everyone! This is Jon, an AI and technology blogger. Today, I'm here to share the news that GitHub Copilot, an AI tool, is now fully operational with a feature to modernize older applications (apps) written in Java or .NET. This feature uses AI to help developers update their old code, helping to speed up and simplify cloud migration. This should be a great help for those who have struggled to update their older systems to the latest environment.
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What is GitHub Copilot's app modernization feature? Explaining the basics for beginners
First, let's briefly explain what GitHub Copilot is. GitHub Copilot is an AI-based coding assistant from Microsoft that helps programmers write code. It acts like an AI companion, suggesting and automatically generating code from your input. This app modernization feature uses Copilot to update older Java (an open-source programming language used in many corporate systems) and .NET (a Microsoft framework used for Windows apps, etc.) apps.
Specifically, AI analyzes legacy code (outdated code that is difficult to maintain) and converts it into a modern form. For example, it automatically suggests strengthening security and cloud compatibility (moving it to a server on the Internet). This feature is provided as an extension for Visual Studio Code, a popular code editor, and can be run within the tools that developers use every day.
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Latest Update: Public Opening in September 2025 and its History
Let's look back at the history of this feature chronologically. First, GitHub Copilot's app modernization feature was announced as a public preview (a test version before general release) for Java on May 19, 2025. This was announced on the official GitHub blog and Microsoft's developer site, and its purpose was to use AI to accelerate the upgrade and cloud migration of Java apps.
Then, around July 12, 2025, a Microsoft Learn page was added with an overview for Java developers and detailed explanations of the features. The biggest news came on September 22, 2025, when GitHub's Changelog announced that app modernization features for both Java and .NET were generally available (GA). This meant that developers could complete app assessment, code conversion, build patching, and service containerization (lightly packaging apps to make them easier to run on the cloud) in days instead of months.
Furthermore, on September 23-24, 2025, the news was reported in media outlets such as InfoWorld and The AI Economy, and was also discussed among the developer community on X (formerly Twitter). For example, the official GitHub account and technical blog posts shared the usefulness of the feature. These updates are based on the latest information as of September 27, 2025.
Main feature updates
- App Rating: AI analyzes old code and points out problems and areas for improvement.
- Code Conversion: Update your Java Maven and Gradle projects and .NET apps to the latest versions.
- Build Patch: Automatically fix build errors (the process of compiling and running an app).
- Containerization: Use tools like Docker to make your apps cloud-ready.
- Agent Mode: A step-by-step guide to modernization using Copilot's agent mode, as featured in our recent guide.
Benefits of this feature and tips on how to use it
Let's take a look at the benefits of this feature and why it's gaining attention. Traditionally, modernizing apps required specialized knowledge and took months of work. However, with Copilot, AI handles the heavy lifting, allowing developers to focus on building new features. This can lead to cost savings and improved security, especially for companies with legacy systems.
To get started, first install the Copilot extension in Visual Studio Code. Next, open the target Java or .NET project and launch a modernization task using the Copilot command. Review and apply the changes suggested by the AI. The official documentation (GitHub Docs) provides detailed instructions for upgrading Java and .NET apps using Maven/Gradle.
- Save time: Months can be reduced to days.
- Cost reduction: Reduced manual work reduces labor costs.
- Error reduction: AI will convert it accurately.
- Ease of cloud migration: Smooth integration with cloud services such as Azure.
However, it is important that AI suggestions are ultimately reviewed by a human. Rather than completely automating the process, it is recommended to add the developer's judgment.
Jon's Summary and Recommendations
I think GitHub Copilot's app modernization feature is a fantastic advancement, using AI to eliminate development bottlenecks. It should make the transition to the cloud era much more accessible, especially for mid-sized companies using Java or .NET. I personally feel that tools like this are furthering the democratization of technology, and I hope they'll support even more languages and frameworks in the future.
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Reference sources
- InfoWorld: GitHub Copilot-backed app modernization available for Java and .NET (released around September 25, 2025)
- GitHub Changelog: GitHub Copilot app modernization is now generally available for Java and .NET (September 22, 2025)
- Microsoft Learn: GitHub Copilot App Modernization for Java Developers (July 12, 2025)
- Microsoft DevBlogs: Announcing Public Preview of the GitHub Copilot app modernization for Java (May 19, 2025)
- GitHub Docs: Upgrading projects with GitHub Copilot
- Related posts from X (formerly Twitter): Updates from official GitHub and developer accounts (around September 23-24, 2025)