Randy Pagels discusses practical strategies for using GitHub Copilot to modernize legacy codebases. This guide covers refactoring, updating libraries, and specific Copilot prompts to keep code updated.

Modernize Legacy Code with GitHub Copilot

Author: Randy Pagels

Posted on Apr 18, 2025

Legacy code isn’t always broken—but it’s often hard to read, maintain, or extend. This guide explores how GitHub Copilot can assist you in bringing legacy codebases up to modern standards, making them more maintainable and efficient without requiring a complete rewrite.

Why Modernize Legacy Code?

Legacy code often uses outdated patterns (e.g., callbacks, deprecated APIs, or inefficient loops) that can slow development and introduce maintenance challenges. Gradually updating these practices helps ensure:

  • Better readability and maintainability
  • Compatibility with new libraries and frameworks
  • Improved performance and security

How GitHub Copilot Can Help

GitHub Copilot offers AI-assisted suggestions to bring your code up to date. Here are practical ways you can use Copilot to modernize legacy codebases:

1. Copilot Chat: Ask for Modernization Help

Interact with Copilot Chat directly in your editor to request updates on specific code patterns. For example:

# Update this function to use async/await instead of callbacks

This prompt helps refactor synchronous or callback-based code to modern patterns like async/await.

2. Copilot Edit: Inline Refactor Requests

Select portions of your code and leave an inline comment. Copilot Edit will then suggest a more up-to-date version. Example:

# Refactor this to use modern Python practices

This feature is useful for cleaning up nested logic, removing deprecated methods, and applying general best practices.

3. Chat Follow-up: Library or API Updates

Legacy code often relies on outdated libraries or deprecated API methods. You can prompt Copilot to migrate to newer APIs:

# Rewrite this to use the latest version of the fetch API and remove deprecated methods

Copilot evaluates the code and provides suggestions using up-to-date standards and libraries.

Extra Prompts to Try

  • # Clean up this loop using modern JavaScript
  • # Remove unused variables and simplify logic
  • # Rewrite this component using React Hooks
  • # Update this SQL query using modern JOIN syntax

These prompts encourage Copilot to apply optimizations and best practices within a variety of languages and frameworks.

Quick Takeaway

Modernizing legacy code is achievable through incremental improvements. GitHub Copilot can help you clean up, refactor, and modernize your codebase step by step—making your software more robust without needing a total rewrite.

Original author: Randy Pagels at Xebia

This post appeared first on “Randy Pagels’s Blog”. Read the entire article here