We usually think of COBOL as a legacy language. But it is a legacy that lives on, maintaining projects that originated as long as 50 years ago. But this is is increasingly unsustainable. We look at the why and how of COBOL project modernization with five pro tips for successful outcomes.

COBOL modernization refers to updating, transforming, or integrating legacy COBOL-based systems with modern technologies, architectures, and practices. The goal is to ensure that business-critical workloads and data locked in mainframe environments remain accessible, maintainable, and cost-effective as IT landscapes evolve. 

Modernization doesn’t always mean replacing COBOL entirely; it often involves incremental improvements, allowing organizations to leverage existing investments while adopting new technology stacks. This approach typically includes methods like rehosting, replatforming, code refactoring, rewriting, or integrating mainframe applications with cloud and microservices technologies. 

Each organization tailors its COBOL modernization path based on legacy complexity, business goals, risk tolerance, and regulatory requirements. Ultimately, COBOL modernization aims to reduce technical debt, mitigate operational risks, and enable the agility required to meet current and future market demands.

Why Modernize COBOL Systems in 2025? 

Here are four compellings reasons:

The Mainframe Talent Gap

Most COBOL developers began their careers decades ago, and a significant proportion of the workforce is nearing retirement age. Replacing their deep domain knowledge is difficult, especially given that few universities or bootcamps now teach COBOL. This growing talent shortage can pose business continuity risks for organizations reliant on legacy environments.

As the mainframe workforce shrinks, knowledge transfer becomes increasingly urgent, and support for critical applications becomes uncertain. This "brain drain" can slow innovation and increase the burden on a small pool of remaining experts. Modernizing legacy systems—by adopting mainstream languages, tools, or cloud platforms—can help organizations attract new talent, reduce reliance on hard-to-hire specialists, and future-proof operations.

Rising Operational Costs

Running COBOL systems on traditional mainframes comes with escalating hardware and software licensing fees, ongoing maintenance contracts, and expensive support services from shrinking vendor pools. These legacy environments often require specialized skills and processes, driving up costs for staffing as well as support infrastructure.

As hardware ages, finding compatible replacement parts or even just updated firmware can be a challenge, further constraining operational flexibility and increasing both direct and indirect costs. Modernization allows organizations to shift critical workloads to commodity hardware, public or private clouds, or to platforms that use standard, widely supported technologies. This can cut operational expenses and reduce capital expenditure on monolithic infrastructure

Competitive Pressures for Agile Delivery

Legacy COBOL systems, designed for stability over speed, can become bottlenecks when new products or regulatory changes require quick adaptation. The traditional waterfall development models common in COBOL environments struggle to keep up with agile and DevOps practices now standard in most IT departments.

Modernizing COBOL systems can enable organizations to adopt CI/CD pipelines, automated testing, and code management practices that underpin agile operations. By refactoring or integrating mainframe applications with modern platforms, organizations can respond more quickly to changing market needs, unlock new features faster, and compete with born-in-the-cloud disruptors. 

Security and Compliance Imperatives

Legacy COBOL applications often run on outdated operating systems with limited support for modern cybersecurity best practices. Old codebases may lack adequate authentication, encryption, or audit mechanisms required by today's compliance frameworks such as GDPR, HIPAA, or PCI DSS. Mainframe hardware and proprietary middleware add complexity, making it harder to apply patches or monitor for threats.

Modernization addresses these security gaps by moving sensitive workloads to environments where regular patches, active monitoring, and advanced threat mitigation are part of standard operations. Replatforming or rewriting COBOL applications allows for the implementation of multi-factor authentication, detailed logging, and integration with enterprise security tools. 

Key Strategies to Modernize COBOL Applications 

Rehosting (Lift and Shift)

Rehosting, often called “lift and shift,” involves moving COBOL applications from mainframe hardware to less expensive and more flexible platforms such as Linux, Windows, or cloud-based environments, usually with minimal changes to the application code itself. This approach relies on emulation or compatibility layers that mimic mainframe behavior, allowing organizations to preserve business logic while avoiding the expense and disruption of a major rewrite. 

A successful rehosting project can quickly reduce operating costs and free workloads from proprietary or end-of-life hardware constraints. However, while rehosting provides a faster path to cost savings and easier hardware management, it typically does little to modernize the underlying code or architecture. 

Replatforming

Replatforming takes the concept of rehosting a step further by adapting COBOL applications to run more natively on modern platforms, often involving modest changes to code or data structures. This process can include migrating data stores, removing dependencies on proprietary middleware, or implementing new runtime environments that better align with cloud, container, or virtualization strategies.

The goal of replatforming is to improve maintainability, enable more efficient scaling, and make it easier to integrate with other parts of the IT ecosystem. By updating application components to use modern runtimes and services, organizations can unlock performance benefits and leverage the strengths of new platforms while still limiting disruptive changes to workflows.

Refactoring

Refactoring COBOL applications involves restructuring and optimizing code without changing external program behavior. This can include breaking monolithic programs into smaller, modular components, removing obsolete routines, and updating interfaces for easier integration with modern systems. Refactoring might also use automated tools to convert code to newer programming paradigms or improve documentation and maintainability.

The primary advantage of refactoring is that it gradually improves code quality while controlling risk and preserving business logic developed over decades. Teams can tackle technical debt while keeping legacy workflows running in production. Over time, refactored COBOL code may become easier to port to other languages or architectures, enabling long-term upgrades or full-scale migrations to modern platforms.

Rewriting

Rewriting is the process of recreating business functionality from a legacy COBOL application using a modern language or architecture, such as Java, C#, or microservices. Instead of translating COBOL code, development teams assess business logic requirements, design new solutions, and implement them using contemporary frameworks and architectural best practices. This path often delivers the greatest long-term flexibility and alignment with current technology.

However, rewriting is typically the most resource-intensive and risky modernization approach, demanding significant effort for requirements gathering, regression testing, and change management. Rewriting becomes more attractive when legacy systems are highly customized, poorly documented, or failing to meet critical business or technical needs.

Hybrid Approaches

Hybrid approaches combine elements of rehosting, replatforming, refactoring, and rewriting to create a tailored modernization path. For example, an organization might rehost less critical workloads for quick savings, refactor select modules for better maintainability, and rewrite high-impact components to deliver new functionality. 

This mixed strategy allows organizations to spread risk, balance budget constraints, and address high-priority pain points incrementally rather than in a single, massive overhaul. Hybrid modernization is particularly effective when priorities or capabilities vary across systems and departments. It supports phased rollouts, parallel workstreams, and continuous improvement.