Application modernization is the process of updating legacy software systems to align with current technologies, architecture, and business needs. It is how teams move from outdated, monolithic applications to scalable, often cloud-native solutions that support modern development practices. When done effectively, modernization can improve performance, security, and agility. This helps to reduce technical debt and create space for future innovation.

Legacy systems often rely on outdated frameworks, rigid architectures, and manual processes that slow down development and limit innovation. They’re harder to maintain, slower to update, and more vulnerable to threats. Modernization addresses these constraints through approaches like cloud-native architectures, microservices, containerization, and automated workflows like continuous integration and delivery (CI/CD) pipelines. It’s a key part of digital transformation, enabling teams to respond quickly to market changes, integrate emerging technologies like AI, and deliver better user experiences.

Understanding how application modernization works, and how GitHub supports it, can help you build better software, faster.

What are the benefits of application modernization?

Companies modernize legacy applications to stay competitive, reduce costs, and improve agility. Legacy systems are often expensive to maintain, difficult to scale, and slow to adapt to changing business needs. Application modernization helps developers move faster, collaborate better, and deliver more secure, reliable software. Whether you are aiming for a full cloud-native transformation or incremental legacy modernization, key benefits include:

Agility and performance: Modular architecture and scalable infrastructure improve system responsiveness and a team’s adaptability to new requirements.

• Developer productivity: Modernized environments enable developers to use tools like GitHub Copilot, CI/CD pipelines, and collaborative workflows to streamline focus on building, not maintaining.

• Security and compliance: Automated code scanning, secure supply chain practices, and infrastructure as code (IaC) improve consistency, auditability, and governance—reducing overall risk.

• Cost efficiency: Cloud application modernization can reduce maintenance overhead and enable long-term savings through optimized resource usage.

• AI and innovation enablement: Modern platforms provide the foundation for integrating AI, predictive analytics, and intelligent automation—helping teams innovate faster and smarter.

Core strategies for application modernization

There’s no one-size-fits-all approach to modernization. Teams choose strategies based on their goals, resources, and technical constraints. A common industry framework to follow is known as the 6 Rs of application modernization:

• Rehost: Move applications to the cloud without changing the code. Also known as “lift-and-shift,” this is often the fastest and least disruptive option, but it may not deliver full cloud-native benefits.

• Refactor: Optimize code for cloud environments without changing functionality. This improves performance and maintainability while preserving core logic.

• Replatform: Make minimal changes to shift to a new runtime or platform. This can improve scalability and reduce operational overhead.

• Rearchitect: Redesign the application to support modern architectures like microservices. This is ideal for teams looking to improve agility and scalability.

• Rebuild: Rewrite the application from scratch using modern frameworks. This is the most resource-intensive option but offers the greatest flexibility.

• Replace: Retire the legacy system and adopt a new solution. This approach is often selected when the current application fails to satisfy business requirements.

Teams often begin with legacy modernization efforts like rehosting or replatforming before moving on to more complex strategies such as rearchitecting or rebuilding.

Choosing the right strategy depends on:

• Business goals: Are you trying to reduce costs, improve performance, or enable new capabilities?

• Technical debt: How complex and outdated is the current legacy system?

• Team capacity: Do you have the resources and time to rearchitect or rebuild?

• Time constraints: How quickly do you need to deliver results?

Modernization patterns like monolith-to-microservices, cloud migration, and exposing functionality via APIs often guide these decisions. For example:

• A monolithic application might be rearchitected into microservices to improve scalability and team autonomy.

• An on-premises system might be rehosted or replatformed to run in the cloud, improving reliability and reducing infrastructure costs.

• Legacy functionality might be exposed via APIs to support integration with modern tools and services.

These patterns help teams modernize incrementally, reducing risk while delivering value.

Key technologies driving application modernization

Several technologies enable modernization. These tools and practices help teams build scalable, secure, and maintainable applications that support continuous improvement.

• Containerization: Containers package applications with their dependencies, making them portable, scalable, and easy to deploy. They support consistent environments across development, testing, and production, reducing configuration issues and speeding up delivery.

• Microservices: Thesebreak applications into smaller, independent services that can be developed, deployed, and scaled separately. This improves agility, supports team autonomy, and enables faster iteration.

• Cloud migration: Moving applications to public, private, or hybrid cloud environments improves scalability, reliability, and cost efficiency. Teams can choose between rehosting, replatforming, or rebuilding based on their goals and constraints.

• CI/CD automation: Continuous integration and delivery (CI/CD) pipelines automate the build, test, and deployment process. This reduces manual effort, improves consistency, and enables faster releases. GitHub Actions provides native CI/CD capabilities that integrate seamlessly with your workflows.

• Infrastructure as code (IaC): A method that allows teams to define and manage infrastructure using code. This improves reproducibility, reduces configuration drift, and supports automated provisioning. Tools like Terraform and GitHub Actions make it easy to integrate IaC into your pipelines.

• GitOps: A framework that uses Git as the source of truth for infrastructure and application configurations. Changes are made through pull requests, enabling version control, auditability, and automated deployment. GitHub’s native support for Git workflows makes it a natural fit for these practices, especially when paired with modern DevOps like CI/CD automation and IaC.

• AI-assisted development: AI tools like GitHub Copilot help developers write, refactor, and test code faster. By generating context-aware suggestions, Copilot reduces manual effort and accelerates development workflows. These capabilities support flexible, resilient systems that enable rapid iteration, improved code quality, and continuous improvement across teams.

Application modernization services and tools

Modernization services typically include assessment, refactoring, migration, and validation. GitHub supports these efforts through integrated developer workflows, automation, and AI-powered tools.

One example is Copilot App Modernization for .NET and Java, which uses agentic AI to combine automation, context-awareness, and developer control. Developers can assess legacy codebases, suggest improvements, and validate changes. This speeds up modernization while maintaining code quality.

GitHub Actions enables seamless CI/CD integration, automating build, test, and deployment processes. Built-in code scanning and security tools help teams catch vulnerabilities early and maintain compliance throughout the software development lifecycle.

These tools form a comprehensive enterprise application modernization solution from initial assessment to secure, scalable deployment.

Use cases and success stories

Application modernization is happening across industries. Organizations big and small use GitHub to modernize legacy systems and improve outcomes. Check out how enterprise application modernization can deliver faster releases, lower costs, and improved resilience with success stories from GitHub customers.

• Neon Bank, a Brazilian digital bank serving over 23 million customers, faced slow, fragmented deployments with their legacy tools. By migrating to GitHub Enterprise and adopting GitHub Actions, they reduced deployment time from six hours to just 10-15 minutes—a 97% improvement. Deployment frequency increased by 25%, and resilience improved through automation and secure CI/CD pipelines. See how Neon Bank streamlined their tech stack with GitHub

• McKesson Labs centralized 25 engineering teams under a unified DevOps stack using GitHub Enterprise. They eliminated over 100 manual processes and saved approximately $350,000 per team within 16 months. Automated security checks and infrastructure as code improved scalability and security across the healthcare organization. See how McKesson Labs transformed their DevOps stack with GitHub Enterprise

• Capillary Technologies, serving 400 retail brands across 35,000 stores, migrated from SVN to GitHub and built a GitOps tool using GitHub APIs. They reduced deployment time from four to five hours to under one hour across five regions, supporting 500-600 deploys per day. Security and developer onboarding also improved significantly. See how Capillary Technologies increased efficiency and security with GitHub

Getting started with application modernization

Modernizing legacy systems improves agility, scalability, and innovation. If you’re considering converting or exploring cloud-native architecture, these steps will help you get started. They’ll help evaluate your current environment and begin implementing application modernization solutions that align with your organization’s goals.

• Assess legacy codebases using GitHub’s integrated tools. Start by identifying which parts of your system are outdated, hard to maintain, or incompatible with modern development practices. GitHub’s code scanning and repository insights can help you surface technical debt and prioritize what to modernize first.

• Automate workflows with GitHub Actions. Once you’ve identified areas for improvement, begin automating build, test, and deployment processes. GitHub Actions supports CI/CD pipelines that reduce manual effort and improve consistency across environments.

• Explore GitHub Copilot App Modernization for .NET and Java. If you're working with legacy code in .NET or Java, Copilot App Modernization can help you refactor and validate code faster using agentic AI. It’s designed to support developers in transforming legacy systems into maintainable, cloud-ready applications.

• Use GitHub Enterprise for secure collaboration at scale. As your modernization efforts grow, GitHub Enterprise provides the governance, security, and scalability needed to support distributed teams. It helps standardize workflows, enforce policies, and integrate with your broader DevOps ecosystem.

While no solution is a one-size-fits-all, these are good starting points for teams looking to adopt application modernization solutions that improve agility, security, and developer productivity.