What Are Legacy Applications? Types, Challenges, and Solutions

With rapidly advancing technology and increasingly high user expectations, companies must regularly upgrade outdated systems.

Companies understandably want to maintain a vital operational system for as long as possible. However, clinging to outdated technology can quickly transform what was once an asset into a liability. Old systems can soon become dangerous, costly, and time-consuming. 

Companies often use archive storage solutions to store data after sunsetting legacy apps. 

Technology has also revolutionized cloud environments and architectures over the past several years, allowing business processes to build, upgrade, update, and manage applications faster through cloud migration software.

Companies continue to utilize legacy programs for a variety of reasons. The expense of updating a legacy application may be prohibitive in some instances. 

In other circumstances, the legacy program may be so tightly connected with other systems that replacing it would be difficult or impossible. Finally, some businesses may be unwilling to adapt, even if there are compelling reasons to do so.

Why do applications become legacy systems?

Not all legacy systems are ancient; some date back only five or ten years. What makes them "legacy" isn’t just age, but whether they’ve become an operational liability rather than an asset.

Here are the most common reasons applications, systems, or technologies end up labeled as legacy:

• They no longer get updates, support, or maintenance from the developers or producers of their programs.
• They are no longer for sale and rely on outdated systems to operate and maintain.
• In the case of hardware, such as mainframes, it can no longer support an organization's software.
• IT specialists with complex, obsolete technical skill sets, such as common business-oriented language (COBOL) programming, must maintain the system. These specialists might be challenging to locate and expensive to hire.
• Repairs take far too long in comparison to new systems.
• Maintenance expenses grow too high to justify continuing.
• They are too vulnerable to security risks and cannot be modified to meet contemporary cybersecurity requirements.

 A legacy program is typically associated with a specific operating system (OS) or coding language. The problem is usually running the legacy application while converting it to newer, more efficient code that uses current technologies and programming languages.

What are the different types of legacy applications?

The typical forms of legacy systems are as follows:

• End-of-life (EOL). The vendor frequently discontinues the product when legacy systems pass their useful phase. That means no more bug fixes, security patches, or compatibility updates; you're essentially flying without a safety net. Microsoft's lack of support for Windows 7 is one example. Businesses using EOL software are vulnerable to cyberattacks, data loss, and compliance violations.
• No updates available. While this is closely similar to EOL, it refers to systems with no upgrades or new versions. You can’t patch them, extend them, or integrate them with newer technologies. These systems usually can’t handle modern data types, lack mobile or API support, and don’t play well with cloud services. Businesses find it tough to change and develop since they must switch to a new provider and build new processes for the same operations. 
• Inability to scale. Legacy systems no longer have the scalability to support a firm’s growth, production, and security requirements. They buckle under pressure and often require manual scaling or resource-intensive fixes. As companies grow and go global, these systems can’t keep up. They limit your ability to serve customers, expand offerings, or respond to new business demands.
• Legacy codebase or language. Apps written in outdated or niche programming languages like COBOL and Pascal pose serious long-term maintenance issues. Even if the code still works, developers who know how to work with it are retiring or shifting to modern stacks.

How do legacy applications differ from modern applications?

Legacy apps are designed with traditional development approaches based on monolithic architectural models. This indicates that the application's code, services, and other components are deeply interwoven, making scaling and adapting to changing contexts more difficult. 

Businesses often continue to rely on legacy applications to meet crucial business demands. However, legacy applications are frequently inefficient, unreliable, and unsuited for achieving digital transformation objectives due to their interconnected designs. 

Modern apps are developed with agile approaches, DevOps practices, modular design, and serverless operational models. These are more flexible, scalable, portable, and resilient than older applications. They enable enterprises to develop custom application development solutions quickly while decreasing time to market and total cost of ownership. 

Modern applications can handle millions of users on demand and run on multiple platforms, including on-premises and cloud-based environments. The contemporary application development approach eliminates much of the operational overhead associated with historical application development. Consequently, teams may concentrate on business logic while delivering higher-quality solutions.

Why are legacy applications still in use?

Businesses stick with legacy applications for various reasons. Some of them are discussed below.

• They are still functional. Many legacy apps continue to function and are critical to a company's everyday operations. They might not find it necessary to constantly replace systems and technologies that are still operational only because they are obsolete.
• Upgrading is expensive. Changing a legacy system or application might not be cost-effective. While retaining old technology may cost businesses more money in the long run, some organizations lack the immediate means to upgrade their systems. Upgrading can also take time since it may necessitate retraining or recruiting new employees to master and incorporate new technology.
• Internal skill gap and fear of disruption. Being able to modernize legacy applications may be a difficult task. Some businesses lack the skill set required to upgrade their systems and deal with the issues that may arise. Migrations can also cause service interruptions, data loss, and a bad end-user experience.
• Resistance to change. Technology isn't always the problem; sometimes, people are. Staff may resist moving away from familiar systems, especially if they've been using them for years. Retraining takes time, and organizational inertia can slow even the best-planned transformation efforts.

Real-world examples of legacy applications

Many companies, such as banks and government agencies, rely on legacy systems. These companies depend on established, consistent, and reusable technologies that are typically complex to develop and expensive to replace. The following are some examples:

• Orion, NASA's spacecraft. 2002-era IBM PowerPC 750X single-core processors power NASA's Orion spacecraft. Orion has been in development since 2000 and was launched for the first time in 2022.
• Internet Explorer (IE) is a browser developed by Microsoft. In January 2020, Microsoft discontinued support for all versions of the IE previous to version 11. Support for Internet Explorer 11 ceased in June 2022. Organizations may use Microsoft Edge's IE mode to access programs and websites that still support IE.
• Mainframes in banking. Many financial institutions still rely on COBOL-based mainframe systems to handle core transactions, account management, and loan processing. The systems are reliable but expensive to maintain, and skilled COBOL programmers are becoming scarce.
• On-premise ERP and CRM systems. Many companies still run early versions of ERP and CRM platforms like Oracle E-Business Suite, SAP ECC, or legacy Siebel systems. Without cloud capabilities, they struggle to meet modern business needs, such as real-time reporting, mobile workforce support, or cross-platform integration.

What are the risks of using legacy systems?

Legacy applications might seem “good enough,” but beneath the surface, they can quietly drain resources, introduce vulnerabilities, and hinder innovation. Here’s a breakdown of the most pressing risks companies face when sticking with legacy tech: 

• Maintenance costs of upkeep and operation. Because of the high costs of changing legacy systems and applications, many businesses continue to utilize them. However, sustaining outdated technology over time can be costly. Developers will not upgrade legacy systems. As a result, they require constant support from the IT infrastructure and staff. These costs may eventually surpass the advantages of sustaining the status quo.
• Performance bottlenecks. When a vendor's software development team no longer supports a program, an operations team may struggle to maintain the product's functionality. As they age, continuing to utilize old systems might decrease performance, increase resource usage, and cause frequent failures and crashes. Maintaining obsolete technology also limits firms from using emerging technologies, reducing their competitive edge compared to more contemporary competitors. Many legacy systems are also incompatible with modern systems, limiting usefulness for firms that use a mix of old and new technologies. 

• Data silos. A data silo is a repository that cannot be integrated or shared between business units. Many legacy software systems are incompatible with modern software, which means that data saved on an older system within a corporation cannot be shared with other departments that use newer technology.
• Compliance risks. Legacy systems may not meet data compliance rules such as the Health Insurance Portability and Accountability Act (HIPAA) or the General Data Protection Regulation (GDPR). Noncompliance with these requirements can result in fines, other penalties, and bad publicity.
• Technical support and security vulnerabilities. Legacy systems receive no technical assistance or upgrades from their developers and must rely on outdated security mechanisms or patches to avoid intrusions. This exposes them to data breaches. According to PKWARE, in a breach in March 2025, the personal information of over 3 million applicants to NYU was exposed due to the potential exploitation of a legacy system.
• Innovation roadblocks. Legacy systems can’t support functions like AI, automation, or remote collaboration. They slow down digital transformation and force teams to settle for “good enough.” The longer you wait to modernize, the further behind you fall.

What is legacy application modernization?

Legacy application modernization is the process of transforming programs developed with outdated software into new apps using cutting-edge technology. Legacy application modernization approaches like application programming interface (API) generation bridge the gap between legacy and modern systems and enhance the value of existing systems. 

Other approaches, like cloud migration, enable apps to be modified or rebuilt to operate in current runtime environments. 

Businesses strive to modernize legacy programs because they rely on obsolete technology, making it difficult to protect, enhance, and transmit critical application components. Replacing or updating old systems is necessary to manage critical business functions effectively. 

Below are some strategies used in legacy application modernization.

Cloud migration solutions

Digital adoption, automation, and migrating old apps to the cloud aid in the monitoring and accounting of corporate operations and procedures. Legacy application data migration boosts performance and organizational competitiveness while assuring improved job execution. This is where cloud migration software comes into play. 

Archive storage solutions

Often, enterprises must preserve their legacy data to maintain compliance with internal corporate laws and policies and applicable legal regulations and policies. They will undoubtedly need to archive both new and old data, but it must be simple to access, manage, and control. This is where archive storage solutions come into play. 

Data frequently preserved in archive storage systems aren't immediately relevant but still have value.

Frequently asked questions about legacy applications

Got more questions? We have the answers.

Q1. Can you modernize a legacy application without rebuilding it?

Absolutely. Strategies like rehosting, replatforming, or refactoring allow businesses to modernize gradually, without rewriting the entire application from scratch.

Q2. What is the most cost-effective way to modernize legacy systems?

The most cost-effective path depends on the app’s complexity and business role. Rehosting or replatforming are generally less expensive than rebuilding or replacing.

Q3. What industries rely most heavily on legacy applications?

Industries like banking, healthcare, government, and manufacturing often depend on legacy systems due to complex regulations, high reliability needs, or long-standing custom software.

Q4. How do I know if it's time to modernize a legacy app?

Key signs include a lack of vendor support, performance issues, rising maintenance costs, integration roadblocks, and an inability to meet security or compliance standards.

Q5. What is the difference between legacy modernization and digital transformation?

Legacy modernization focuses specifically on updating outdated systems, while digital transformation is a broader initiative that includes rethinking processes, tools, and culture to fully leverage modern technology across the organization.

Q6. Can legacy applications integrate with modern systems?

In some cases, yes, through middleware, APIs, or integration platforms. However, integration is often limited, brittle, or costly, which is why many businesses opt for modernization to enable seamless, scalable connectivity.

Leaving the legacy behind

Several obstacles must be overcome while working with legacy programs in today's ever-changing technological environment. An organization's capacity to innovate and respond to shifting market needs is often hampered by its aged systems' inflexibility, scalability, and inefficiency. 

But since firms are often comfortable with their legacy system, is it time to upgrade, or should you stick with what has served you well for years?

Ready to modernize smarter? Discover how AI is transforming legacy system modernization from faster code refactoring to intelligent migration planning.

This article was originally published in 2023. It has been updated with new information.