Old software does not always look broken from the outside. It may still run, still support daily work, and still hold important business data. The trouble starts when every small update takes too long, integrations feel painful, security becomes harder to control, or the team spends more time working around the system than improving it.
That is where legacy app modernization companies come in. They help businesses rebuild, refactor, migrate, redesign, or gradually improve outdated applications without losing the logic that keeps the company moving. This list looks at companies that work with older systems in a practical way - not just by replacing everything for the sake of it, but by finding a smarter path toward better performance, cleaner architecture, easier maintenance, and room for future growth.
At Gilzor, we provide legacy app modernization services for products that need a more stable technical base, cleaner architecture, or a clearer path for future development. Our work is connected with custom software development, business analysis, consulting, web and mobile development, QA, and support. We focus on the parts of the system that affect delivery speed, maintenance, integrations, and product reliability.
Our team reviews your current architecture, identifies technical limitations, and plans gradual improvements or rebuilds where necessary. We also support migration to newer technologies, proof of concept development, release process stabilization, and post-launch maintenance. This helps reduce unnecessary disruption while making the application easier to update, test, and extend over time.
Andersen works with legacy app modernization through a fairly broad technical scope, covering older codebases, system migration, API updates, data transfer, QA, and compliance-related changes. Andersen is not limited to one modernization route. They work with refactoring, rehosting, replatforming, rearchitecting, rebuilding, and encapsulation.
For legacy applications, Andersen also pays attention to the less exciting parts that often matter most: estimates, timelines, integration points, and quality checks. They can review system performance, rewrite outdated components, split monoliths into microservices, move datasets to newer platforms, and connect old systems with newer tools.
Euvic handles legacy systems modernization as part of a wider digital transformation service. Their work covers outdated applications, IT environments, workflows, user experience, Agile and DevOps processes, AI, automation, and digital strategy.
The company uses a 7-step legacy application modernization framework and works with several modernization methods, including rehosting, rearchitecting, replacing, refactoring, and retiring. Euvic also puts a lot of weight on system and data analysis before changes begin, which is sensible because old systems often carry business logic that is easy to break and hard to rebuild from memory.
Luxoft focuses on complex legacy modernization, especially when older systems are business-critical and cannot be moved casually. Their service is closely tied to mainframe modernization, cloud-ready architecture, QA automation, continuous integration, and the preservation of existing business logic.
Luxoft works with legacy technologies such as z/OS COBOL, JCL, IMS, CA Gen, and related environments. They also build their own modernization tools, including compilers and code converters, when standard approaches are not enough. Their work include migration planning, code transformation, operating system changes, performance optimization, database adaptation, and CI/CD setup.
Mobian works mainly with custom mobile applications, with a focus on business apps in MedTech and FinTech. For legacy app modernization services, Mobian’s role fits around updating older mobile products, improving how users move through the app, and making sure the product still supports current business needs. Their work is close to the product side, so modernization is not only about code cleanup. It also includes UX, analytics, platform updates, and the small decisions that make an older app easier to use again.
Mobian Studio handles projects across Android and iOS, with full-cycle development from early planning to launch. Older mobile apps often need this kind of broader review because a technical update alone may not fix the real issue. Mobian can help refresh the interface, rebuild outdated parts of the application, add product analytics, and keep the client updated through the process.
Vention covers legacy application modernization through consulting, code refactoring, cloud migration, rearchitecting, reengineering, rebuilding, replacing, and integration work. Their service is built around older systems that need cleaner code, stronger architecture, better scalability, or a more modern infrastructure setup. Vention also works with monolith-to-microservices transitions.
Technical depth is a clear part of Vention’s modernization work. Vention also works with APIs, DevOps, containerization, automation, and CI/CD. That gives them room to modernize not only the app itself, but also the way it is deployed, tested, connected, and maintained.
A-listware works with older systems that no longer match how a company operates today. Their modernization work is usually tied to existing platforms that need better stability, cleaner connections with newer tools, and fewer limits around future changes.
They support custom development, application upgrades, cloud migration, integration, data-related work, and long-term maintenance. That mix matters for companies with legacy applications that sit at the center of daily operations, because the app itself is rarely the only thing that needs attention.
Devox Software works with legacy modernization across applications, infrastructure, databases, integrations, and delivery pipelines. Devox Software focuses on older enterprise systems that have become fragmented, hard to update, or too expensive to keep running in their current shape. Their modernization work covers system assessment, technical debt review, target architecture design, and roadmap delivery, so the process starts with understanding what is actually inside the legacy environment before changing it.
The company also brings cloud, DevOps, automation, AI-assisted code analysis, and security work into modernization. Devox Software can move legacy systems toward modular and cloud-native architecture, add API layers, update CI/CD processes, refactor code, modernize databases, and rebuild parts of a system that no longer support current operations.
OSKI Solutions modernizes older enterprise systems by rebuilding weak parts, improving architecture, and moving workloads toward more flexible environments.They work with legacy platforms that have become harder to maintain or connect with newer tools. Their modernization service covers monolith decomposition, microservices, cloud migration, API work, and custom software development, with a focus on keeping core operations stable during the transition.
The technical side of OSKI Solutions is broad enough for both backend-heavy and user-facing modernization. They work with .NET, Node.js, React, Angular, Vue, Azure, AWS, Docker, and CI/CD, which gives them room to update old systems from several angles.
NIX United treats legacy modernization as more than a code update. They connect it with cloud migration, system integration, security, maintainability, scalability, user experience, and long-term cost control.
A careful part of NIX United’s approach is the attention to choosing the right level of change. A stable system may only need rehosting or encapsulation, while a heavily outdated monolith may need refactoring, rearchitecting, or full rebuilding. NIX United also covers the planning side of modernization, including system audits, business goals, tech stack selection, team setup, scope planning, data migration, user training, and post-release monitoring.
Itransition works on application modernization for companies that need to update older software without losing the business logic already built into it. Itransition covers full app renovation as well as smaller improvements, so the work may involve architecture redesign, migration, containerization, refactoring, UI updates, functionality changes, and integration with newer systems.
Before changing the system, Itransition reviews the legacy application, its architecture, code, documentation, dependencies, and current business needs. From there, they can choose a modernization model, plan the technical work, test the updated solution, collect user feedback, and support the product after release.
Telliant Systems modernizes legacy applications that are hard to maintain, slow to update, or tied to older infrastructure. Telliant Systems works with re-architecting, cloud migration, UI/UX upgrades, API-first design, microservices, DevOps, and data modernization. Their modernization service also covers older technologies such as COBOL, RPG, Assembler, C/C++, IBM mainframes, and Unisys, which gives the company a place in more complex enterprise environments.
They take an iterative route rather than treating modernization as one large technical jump. Telliant Systems assess current systems, build a modernization roadmap, move applications to AWS, Azure, or GCP, redesign old interfaces, create connectors between legacy and modern tools, and containerize applications for more stable deployment.
Itexus works with legacy app modernization mainly in financial services, including banking, trading, WealthTech, lending, payments, insurance, and digital assets. Itexus focuses on systems where old architecture, fragile integrations, compliance pressure, and tightly coupled code make product changes slow.
Itexus uses service wrappers, integration layers, the Strangler Fig pattern, anti-corruption layers, automated regression testing, contract testing, and gradual rollouts with rollback paths. They also use AI-assisted analysis for systems with incomplete documentation, but keep manual engineering oversight around refactoring and modernization decisions.
Softura works with legacy application modernization for enterprises that have older systems taking too much budget, time, and internal attention. They start with an application portfolio assessment, looking at business value, technical debt, risk, and modernization readiness before choosing a path forward. The company works with several modernization routes, including rehost, refactor, rearchitect, rebuild, and replace.
Softura’s modernization work is closely tied to cloud infrastructure, business continuity, and long-term operating costs. They move older applications into cloud-ready, cloud-optimized, or cloud-native environments, while using phased migration to avoid a sudden cutover.
Rishabh Software works on application modernization for companies that need to upgrade legacy software while keeping business logic and data safe. Rishabh Software handles cloud enablement, application reengineering, UI/UX modernization, and monolith-to-microservices refactoring.
They also work with application assessment, business rules mining, remediation, serverless architecture, API development, DevOps, and microservices. Rishabh Software uses technologies such as Angular, Flutter, Laravel, .NET Core, Node.js, React Native, React, and Spring.
21Century.Tech is an AI-native software studio that works with senior engineers and AI-assisted development workflows. For legacy app modernization services, 21Century.Tech fits around refactoring, rebuilding older features, improving test coverage, and cleaning up code that has become slow to change.
Older applications often need more than a quick technical patch, and 21Century.Tech’s setup is built around moving through that work in shorter delivery cycles. They can help with legacy refactors, third-party integrations, production-ready code, CI/CD, documentation, tests, and deployment to the client’s infrastructure or their own.
SoftPro is a Warsaw-based software company working with custom software, web applications, cloud development, and AI solutions. SoftPro’s technical background is closely tied to Azure, ASP.NET, .NET Core, and the wider Microsoft stack.
SoftPro helps rebuild older web applications, move parts of a system to the cloud, improve backend structure, and update user-facing layers with modern frontend tools. Their team also works with CMS platforms, database-heavy systems, CRM and HRM products, support systems, SaaS ETL platforms, and business portals.
HCLTech provides application modernization services for large application estates where old systems have hidden dependencies, technical debt, and limited visibility. They use GenAI and Agentic AI to support portfolio analysis, dependency discovery, technical debt management, and modernization planning.
Enterprise systems with mainframe, midrange, cloud, and mixed application layers need careful handling, and HCLTech covers that wider landscape. Their services include AI-driven portfolio lifecycle management, legacy app modernization, mainframe and midrange modernization, cloud-aligned transformation, and modular modernization.
Net Devs works with enterprise software development through senior-led teams and AI-assisted delivery. They keep architecture, priorities, risk decisions, and final quality in the hands of experienced engineers, while AI agents help with drafting, testing, documentation, and delivery tasks.
The company is stack-agnostic and works across .NET, JVM, Node, Python, Go, React, Angular, Vue, TypeScript, Azure, AWS, and GCP. Net Devs can modernize older enterprise systems by improving backend structure, updating front-end layers, adding automated and manual QA, and moving applications toward cloud-native architecture.
Legacy app modernization is rarely about making old software look new for the sake of it. Most of the time, the pressure is more basic: the system is slow to change, hard to connect, expensive to support, or too risky to keep patching forever. A good modernization partner should be able to look at the existing product without rushing into a full rebuild. Sometimes refactoring is enough. Sometimes the right move is cloud migration, API layering, rearchitecting, or replacing only the parts that keep slowing everything down.
The companies in this list approach legacy app modernization services from different angles. Some focus on enterprise systems, mainframes, and cloud transformation. Others are better suited for mobile apps, fintech platforms, Microsoft-based systems, AI-assisted refactoring, or smaller product teams that need practical engineering help. The choice should come down to the current state of the application, the risk level, the industry requirements, and how much change the business can handle at once. Old software can still hold a lot of value. The real work is knowing what to keep, what to clean up, and what finally needs to go.
