21 Best Legacy System Modernization Companies in Europe (2026)

Gilzor develops custom software for startups, small and medium businesses, and product companies. Our projects usually begin with product validation and business analysis, then continue through UI/UX design, development, testing, launch, and long-term support. Instead of treating these as separate services, we combine them into a single product development process that follows business goals from the first idea to ongoing improvements.

Our scope extends to legacy system modernization, including application upgrades, architecture optimization, cloud migration, interface improvements, and the integration of new functionality without replacing entire systems. Alongside engineering work, we support technology planning, proof of concept development, quality assurance, and maintenance to help businesses extend the value of software they already rely on.

Intellias works with organizations that need to modernize existing applications while keeping business operations running throughout the process. Their approach combines consulting, engineering, cloud expertise, and product strategy to help companies evaluate legacy environments, reduce technical debt, and update software in stages rather than through large-scale replacement. Modernization projects cover planning, migration, architecture improvements, and ongoing platform evolution.

Application modernization is treated as a business initiative as much as a technical one. Development teams assess application portfolios, define modernization priorities, prepare systems for cloud adoption, redesign user experiences, and support long-term transformation with engineering and project management. This structured approach allows organizations to update critical software while balancing cost, operational continuity, and future scalability.

Oski develops software solutions for enterprises and startups across industries including logistics, travel, fintech, education, insurance, and e-commerce. Their work covers the full software lifecycle, from planning and development to deployment and ongoing maintenance. Projects combine cloud technologies, frontend engineering, AI integration, and content management systems to build applications that support everyday business operations.

Modernizing legacy software is part of their broader software engineering practice. Existing systems can be updated through cloud migration, infrastructure improvements, application redesign, DevOps implementation, and AI-powered functionality where it supports business needs. Development teams focus on creating software that is easier to maintain, integrate, and expand as business requirements change.

Dreamix works with legacy application modernization through audits, reengineering, migration, and long-term system improvement. Their teams review existing infrastructure, codebases, dependencies, security gaps, and performance issues before deciding which parts of a system should be updated, moved, rebuilt, or kept in place. This makes their work more focused on practical modernization than on replacing everything at once.

For older applications, Dreamix supports changes such as architecture redesign, cloud migration, API integration, database migration, and technology stack updates. Existing business logic can be preserved while outdated parts are moved toward more manageable structures, including cloud-native systems, microservices, and event-based architecture. Their approach is especially relevant for companies that need to keep operations stable while gradually improving critical software.

SoftPro develops custom software for businesses that need web applications, cloud systems, AI features, and process improvements. Their work is built around the Microsoft stack, including Azure, ASP.NET, .NET Core, and related backend technologies. Alongside development, they handle frontend, backend, and CMS work, which makes them relevant for companies that need to update older systems instead of keeping disconnected or outdated tools in place.

Legacy modernization fits into their focus on improving business processes through custom development and cloud-based solutions. Older applications can be rebuilt, extended, or moved to more current platforms with attention to scalability, security, and integration. Their experience with web applications, cloud development, AI, CRM/HRM systems, support systems, and SaaS platforms gives them a practical base for modernizing software that has become hard to maintain or expand.

Boldare focuses on legacy code modernization with AI-supported workflows, especially for teams that need to update old systems without stopping production. Their process starts with a readiness scan, where technical debt, dependencies, outdated packages, undocumented modules, and migration risks are reviewed before any implementation begins. This gives engineering teams a clearer view of what should be changed first and how much risk the migration may involve.

Modernization work is handled in stages rather than through a full rewrite by default. Boldare uses AI agents for code transformation, documentation generation, test coverage, and dependency checks, while human review remains part of each checkpoint. Their approach is aimed at systems where legacy code blocks new features, AI adoption, or regular product development, and where incremental migration with feature flags is safer than a single large cutover.

Mobian Studio builds dedicated engineering teams for companies that need mobile, AI, backend, and cloud work without hiring a full in-house team. Their delivery model is split between outsourcing, where they manage the project from planning to release, and outstaffing, where their engineers join an existing team. Across both models, the focus stays on clean architecture, documented code, and clear communication during development.

Legacy system modernization fits into their work through legacy integration, scalable architecture, and post-launch support. Instead of pushing full replacement by default, they connect new systems with the tools a business already uses and rebuild only when it makes practical sense. Their teams can support modernization through APIs, cloud infrastructure, backend development, QA, AI automation, and ongoing maintenance after release.

Sigma Software provides legacy modernization and migration services for companies that need to update old systems without losing business continuity. Their work usually starts with assessment and consulting, where they review system functionality, dependencies, bottlenecks, UX, maintainability, and business fit. Based on this review, they shape a modernization path that may include enhancement, migration, re-platforming, consolidation, or a gradual phase-out of outdated software.

Modernization projects can cover cloud migration, monolith-to-microservices migration, DevOps changes, data engineering, software reengineering, and UI/UX updates. Sigma Software also works with targeted improvements when a full replacement is not the right option. This makes their approach useful for businesses that want to remove specific blockers, extend the life of existing software, or replace legacy systems step by step.

Infosys works with large-scale application modernization, legacy modernization, cloud transformation, and enterprise digital programs. Their modernization work is tied to complex business systems, including ERP platforms, mainframes, trading solutions, banking applications, insurance systems, and customer engagement platforms. Projects often involve moving older systems to modern enterprise platforms, improving application development speed, and supporting wider digital transformation plans.

For legacy system modernization, Infosys brings together application development, cloud services, applied AI, low-code adoption, SAP S/4HANA migration, and mainframe modernization. Their experience is most relevant for enterprises with large application portfolios, regulated environments, and systems that cannot be interrupted during migration. Modernization can involve reducing technical debt, improving total cost of ownership, and helping core systems support newer business and data needs.

Capgemini supports legacy modernization through AI-assisted analysis, documentation, code transformation, and migration. Their CAALM approach with Pega is built for enterprise systems where old applications need to be understood before they can be moved or rebuilt. Work starts with application landscape assessment, then continues through feature analysis, business rule extraction, gap discovery, implementation, data migration, and testing.

For companies with complex legacy software, Capgemini focuses on turning existing application logic into clearer documentation and a more structured modernization plan. AI is used to analyze code, extract business rules, support data migration, and verify similar functions during testing. This makes their work relevant for enterprises that need cloud-native applications but cannot treat modernization as a simple rebuild.

Net-devs builds enterprise software with senior engineers leading the work and AI agents supporting drafting, testing, and delivery. Their teams cover enterprise development, AI engineering, cloud platforms, and modern frontend development across different stacks. Architecture, delivery decisions, and final quality stay with senior engineers, while AI is used to speed up parts of the process without removing human review.

Legacy modernization fits their model when older systems need careful engineering rather than a rushed rewrite. Existing applications can be assessed, redesigned, rebuilt, connected to cloud infrastructure, or extended with AI-supported workflows. Their stack-agnostic approach also helps when a legacy system does not fit neatly into one technology path and needs practical decisions around architecture, risk, and long-term maintenance.

Brainhub works with legacy application modernization for companies that need to improve old systems without stopping daily operations. Their teams focus on problems such as slow feature delivery, scaling limits, outdated technologies, poor integrations, and security risks in older codebases. Before changing the system, they audit the application and choose a modernization scope that fits the business, timeline, and budget.

Modernization work is guided by their delivery framework, which puts attention on stable releases, project governance, and business-focused engineering decisions. Instead of treating legacy work as only code cleanup, Brainhub connects technical changes with practical outcomes, such as better release speed, safer integrations, improved scalability, and easier maintenance. This makes them relevant for companies that want to reduce technical debt without taking on the risk of a full rebuild.

21century.tech builds software with an AI-supported engineering workflow, where human developers lead architecture, business logic, code review, and quality control while AI helps with code generation, test coverage, documentation, and repetitive development work. Their tone is direct, and their delivery model is built around shipping usable software faster without removing human responsibility from technical decisions.

For legacy system modernization, 21century.tech is relevant for teams that need refactoring, faster feature delivery, or a cleaner path out of outdated code. Their work can support legacy code refactors, API integrations, documentation, testing, and production-grade updates where older systems need practical improvement rather than long planning cycles.

Inoxoft provides custom software development with a focus on senior technical advisory, AI-enabled execution, and structured delivery. Their teams work across web, mobile, AI, data, QA, UI/UX, and technical audits, with attention to architecture, scalability, security, and cost efficiency. The company also supports different delivery models, including outsourcing, dedicated teams, staff augmentation, and product development.

Legacy modernization fits into Inoxoft’s work through technical audits, architecture review, software integration, security checks, and custom redevelopment. Older systems can be reviewed for bottlenecks, outdated structures, security risks, and performance issues before changes are made. Their approach is suited to companies that need to improve existing software, replace parts of a legacy system, or build a more stable technical foundation for future product work.

Atos works with enterprise modernization through low-code and no-code platforms, helping organizations update applications, processes, and workflows without relying only on traditional development models. Their low-code services cover consulting, governance, architecture advisory, application modernization, process re-engineering, workflow automation, BPM, CRM implementation, and AI-powered applications.

For legacy systems, Atos uses low-code platforms to modernize outdated applications and business processes in a faster, more structured way. Their teams help enterprises move from older IT models toward more flexible systems, often through cloud migration, cloud-native apps, DevOps, AI, and agile delivery. This makes them relevant for large organizations that need to modernize internal tools, end-of-life applications, and business workflows while keeping delivery manageable.

A-listware provides software development, consulting, and dedicated team services for companies that need extra engineering capacity or support with complex IT systems. Their work covers custom software, application services, testing, UI/UX, infrastructure, data analytics, cybersecurity, and managed support. Besides, A-listware helps clients build remote development teams, which can be useful when modernization requires long-term engineering involvement rather than a one-time project.

Legacy system modernization is part of their software development offering. Existing systems can be updated through software audits, cloud application development, custom redevelopment, infrastructure support, testing, and security improvements. For businesses working with older platforms, A-listware can help modernize applications while keeping the wider IT environment stable and supported.

SII Group supports companies with application development, software maintenance, cloud migration, software package integration, and DevOps. Their work is focused on helping organizations build and transform application assets while keeping business needs, security, flexibility, and long-term maintainability in view. Alongside custom development, SII Group works with ERP and CRM systems, cloud-native architectures, microservices, and agile delivery models.

For legacy modernization, SII Group updates older systems so they no longer slow down innovation or make changes harder than they need to be. Their teams handle technology updates, new feature integration, cloud migration, application redesign, platform migration, and DevOps improvements. Modernization can also include software maintenance, testing, security work, and support for smoother transitions from existing systems to more flexible architectures.

LenGreo is mainly known as a marketing and tech partner, but their service scope includes website development, custom web development, and legacy software modernization. Their work combines business analysis, research, prototyping, design, development, QA, support, and digital strategy. This makes them more relevant for companies that need modernization connected with a wider business or digital growth plan, not only backend engineering work.

For legacy system modernization, LenGreo focuses on updating, optimizing, and scaling outdated systems so they can work with current technologies and business needs. Existing software can be improved through technical updates, better structure, web development, UX changes, QA, and support. Their background in marketing and lead generation can be useful when modernization is tied to a website, customer journey, digital platform, or online sales process.

Cognizant works with AI-led legacy modernization for large organizations that need to update complex systems, reduce technical debt, and prepare infrastructure for newer digital and AI use cases. Their modernization work covers mainframes, cloud migration, application modernization, data modernization, and enterprise platforms. Cognizant uses its own AI-powered tools as well to support analysis, business rule extraction, engineering workflows, and modernization planning.

Legacy modernization projects can involve moving mainframes to cloud platforms, reengineering old applications, improving data flows, and building cloud-native architectures. Their approach is especially relevant for companies with systems that support critical operations in banking, insurance, logistics, retail, and other enterprise sectors. Cognizant focuses on controlled modernization, traceability, parallel run strategies, and reducing risk while older systems are replaced or improved.

Itexus develops software for insurance and financial companies, with a strong focus on modernization, automation, integrations, and customer-facing digital tools. Their work covers insurance platforms, banking systems, digital wallets, trading products, lending software, CRMs, billing tools, document management, fraud analysis, and mobile apps. Because many of these systems deal with sensitive data and regulated workflows, their projects often include security, compliance, data migration, and long-term support from the start.

For legacy system modernization, Itexus works with outdated financial and insurance software that needs to become easier to maintain, integrate, and scale. Older systems can be assessed, migrated, rebuilt in parts, connected through APIs, moved to the cloud, or extended with automation and analytics. Their modernization approach is especially relevant for companies that need to improve core operations without losing control over data, compliance, or existing business logic.

ELEKS provides legacy software modernization services for companies that need to update core systems, improve performance, and reduce the limits created by old architecture. Their work includes application re-engineering, cloud computing, DevOps, product and service design, AI, machine learning, automation, cybersecurity, and software audit. Projects are usually tied to practical goals such as better scalability, easier maintenance, stronger security, and smoother user experience.

Modernization with ELEKS can involve updating the technology stack, redesigning architecture, improving the SDLC, moving systems to the cloud, and adding intelligent automation where it makes sense. Their teams work across industries such as finance, healthcare, logistics, energy, government, insurance, and retail, which makes them suitable for organizations with complex systems and strict operational requirements. The focus is not only on replacing old code, but on making the system easier to support and adapt over time.