Many businesses still rely on software that has been running for years, sometimes even decades. While these systems often continue to support daily operations, they can also slow down growth, make integrations more difficult, and increase maintenance costs over time. Modernizing them is rarely about replacing everything at once. More often, it's about improving what already exists while keeping business processes running smoothly.

This guide highlights legacy system modernization companies in Germany that help organizations update existing software, migrate to newer technologies, improve system architecture, and extend the life of critical business applications. It also covers what to look for when comparing providers and how to choose a partner that fits long-term business goals.

1. Oski Solutions

OSKI develops custom software for businesses that need modern digital products, long-term technical support, or improvements to existing systems. Our work covers the full development process, from planning and engineering to deployment and maintenance, with a focus on building software that fits business requirements and can grow over time. Providing legacy system modernization in Germany, we work with organizations that want to modernize existing applications while introducing current technologies and development practices.

Our scope includes cloud platforms, frontend development, artificial intelligence, and content management systems. Projects span industries such as travel, logistics, e-commerce, education, fintech, and insurance, where software often needs to integrate with existing environments and support changing business needs. Alongside development, we help organizations improve application architecture, modernize technology stacks, and maintain software after launch.

Key Highlights:

• Custom software development

• Legacy system modernization

• Cloud and DevOps expertise

• AI integration and machine learning solutions

• Frontend and UI/UX development

• Umbraco and WordPress development

• Software deployment and maintenance

• Experience across multiple business sectors

Services:

• Legacy system modernization

• Legacy code refactoring

• Cloud migration services

• Microservices architecture design

• Enterprise application integration

• Comprehensive IT audit

• Automated regression testing

• Post-modernization support

• Data migration services

• Security vulnerability assessment

Contact Information:

• Website: oski.site

• E-mail: [email protected]

• LinkedIn: www.linkedin.com/company/oski-solutions

• Address: Kaupmehe tn 7, 10114 Tallinn, Estonia

• Phone: +48571282759

2. SUPREMATIC

SUPREMATIC focuses on software development with a strong emphasis on legacy system modernization. Existing business applications are updated through practical modernization strategies that help organizations keep essential systems running while introducing newer technologies where they add value. Their work often involves improving software architecture and preparing applications for future development instead of replacing them all at once.

Over the years, the team has worked with enterprise software built on technologies such as Java, .NET, JavaScript, Node.js, and Erlang. Depending on the project, modernization may include moving from monolithic applications to microservices, migrating workloads to cloud environments, or connecting legacy software with modern platforms through APIs. Technical consulting and implementation are both part of their delivery, allowing businesses to modernize systems step by step.

Key Highlights:

• Legacy system modernization

• Application modernization

• Enterprise software development

• Cloud migration

• Microservices architecture

• API integration

• DevOps expertise

• Experience with Java, .NET, JavaScript, and Erlang technologies

Services:

• Legacy software modernization

• Application modernization

• Cloud migration

• Microservices implementation

• API development and integration

• Enterprise software development

• DevOps services

• Software consulting and technical supervision

Contacts:

• Website: suprematic.de

• E-mail: [email protected]

• Address: Hospitalstraße 35, 70174 Stuttgart, Germany

• Phone: +49 711 998-85320

3. SoftPro

SoftPro builds business software with an emphasis on modern technologies and custom development. Their projects range from web applications to cloud-based platforms, giving organizations the flexibility to improve existing systems or develop new ones around current business requirements. Modernization is part of that work, especially when older applications need to be updated without disrupting established processes.

Cloud technologies, Microsoft development tools, frontend frameworks, and artificial intelligence are part of their technical stack. Beyond software engineering, they develop business portals, CRM and HRM systems, SaaS products, and internal support platforms. This combination of technologies and business applications allows them to modernize software while adapting it to changing operational needs.

Key Highlights:

• Custom software development

• Legacy system modernization

• Cloud-native development

• Web application development

• Artificial intelligence solutions

• Microsoft technology expertise

• Business software development

• Scalable application architecture

Services:

• Legacy system modernization

• Custom software development

• Web application development

• Cloud development

• Cloud migration

• Artificial intelligence solutions

• Software architecture

• Software support and maintenance

Contacts:

• Website: soft-pro.pl

• Address: Mazowieckie Voivodeship, 13 Erasmus Ciolka St. 401, Warsaw, Poland

4. Groenewold IT Solutions

Groenewold IT Solutions specializes in modernizing legacy software for businesses that want to replace outdated systems without disrupting daily operations. Their approach is built around gradual migration, allowing organizations to preserve existing business logic while updating technologies, improving system architecture, and reducing technical debt. Instead of relying on a full replacement, they modernize applications in stages, with parallel operation and careful planning throughout the process.

Depending on the condition of the system, the team works with refactoring, replatforming, cloud migration, API integration, or complete redevelopment when required. Alongside implementation, they carry out code analysis, data migration, documentation, and knowledge transfer to help businesses maintain and extend their software after modernization.

Key Highlights:

• Legacy system modernization

• Step-by-step migration approach

• Legacy code analysis

• Data migration and system integration

• Cloud migration

• API development

• Modernization of Delphi, VB6, COBOL, and Access applications

• Software architecture modernization

Services:

• Legacy system modernization

• Legacy code analysis

• Code refactoring

• Replatforming

• Cloud migration

• Data migration

• API and system integration

• Software architecture modernization

Contacts:

• Website: www.groenewold-it.solutions

• Instagram: www.instagram.com/bjoerngroenewold

• LinkedIn: www.linkedin.com/company/groenewold-it-solutions

• Twitter: x.com/GroenewoldITS

• Facebook: www.facebook.com/people/Groenewold-It-Solutions/61575304511040

• Address: Mühlenstraße 157, 26789 Leer (Ostfriesland)

• Phone: +49 491 960 999 00

5. Net-devs

Net-devs develops enterprise software using a delivery model where senior engineers oversee projects while AI supports development, testing, and implementation tasks. Their teams work across different technology stacks instead of focusing on a single platform, allowing projects to be planned around technical requirements rather than predefined tools. This makes their engineering approach suitable for both new software development and the modernization of existing business systems.

As a rule, the company works with cloud-native platforms, enterprise applications, frontend development, and AI engineering. Delivery follows a structured process that begins with discovery and architecture planning before moving through prototyping, implementation, testing, deployment, and continuous improvements. Ongoing development remains part of the lifecycle, helping organizations adapt software as business priorities evolve.

Key Highlights:

• Enterprise software development

• AI-assisted software engineering

• Senior-led development teams

• Cloud-native architecture

• Multi-cloud expertise

• Stack-agnostic development

• Frontend engineering

• Continuous software delivery

Services:

• Enterprise software development

• AI engineering

• Cloud and platform engineering

• Frontend development

• Software architecture

• Quality assurance and testing

• Deployment and ongoing support

• Product discovery and prototyping

Contacts:

• Website: net-devs.com

• E-mail: [email protected]

• LinkedIn: www.linkedin.com/company/net-devs

• Address: Obrzezna 1D, 02-691 Warszawa

• Phone: +48 571 282 759

6. Arvato Systems

Arvato Systems helps organizations modernize legacy applications by combining software modernization with AI-supported documentation and knowledge transfer. Their approach addresses one of the common challenges of older business systems - limited documentation and growing maintenance complexity - while preparing applications for future development. This work is particularly relevant for industries that continue to rely on long-established enterprise platforms.

Rather than focusing only on code migration, the company supports the full modernization process, including application documentation, legacy code updates, and migration to modern environments. Existing documentation, architecture information, and business knowledge can be incorporated into the process, allowing modernization projects to build on what organizations already have. Their experience includes projects for insurance and financial services, where reliability, compliance, and long-term system support are essential.

Key Highlights:

• Legacy application modernization

• AI-supported application documentation

• Knowledge transfer

• Legacy code modernization

• Application migration

• Experience with enterprise legacy technologies

• Insurance and financial services expertise

• AI-assisted modernization process

Services:

• Legacy application modernization

• Application documentation

• Legacy code modernization

• Application migration

• AI-supported documentation

• Knowledge integration

• Software modernization

• Enterprise application services

Contacts:

• Website: www.arvato-systems.com

• E-mail: [email protected]

• Instagram: www.instagram.com/company/arvato-systems

• LinkedIn: www.linkedin.com/company/arvato-systems

7. Andersen

Andersen works with legacy system modernization as part of a broader software engineering and digital transformation scope. Their modernization work covers outdated core systems that need better performance, lower technical debt, stronger compliance, or smoother integration with newer platforms. Rather than treating every old system the same way, they assess what should be changed, how deep the changes need to go, and which parts of the software can be improved without unnecessary rebuilds.

Their services include legacy code refactoring, component rewriting, system migration, integration upgrades, data transfer, and quality assurance. Andersen also supports companies with modernization planning, architecture reviews, compliance updates, and change management, which makes their role closer to a full-cycle engineering partner than a narrow migration vendor. Their work fits organizations that need both technical implementation and structured guidance before modernization begins.

Key Highlights:

• Legacy application modernization

• Full-cycle software engineering

• Digital transformation consulting

• Legacy system assessment

• Compliance-focused modernization

• System migration

• Integration upgrades

• Quality assurance

Services:

• Legacy system modernization

• Legacy software reengineering

• Code refactoring

• System migration

• Data transfer and optimization

• API integration

• Compliance updates

• Quality assurance

Contacts:

• Website: andersenlab.com

• E-mail: [email protected]

• Instagram: www.instagram.com/andersen.global

• LinkedIn: www.linkedin.com/company/andersen-lab

• Twitter: x.com/AndersenLabs

• Facebook: www.facebook.com/AndersenSoftwareDev

• Address: 3 Rosa-Bavarese St., Munich, 80639, Germany

• Phone: +49 22 198 253 169

8. 21century.tech

21century.tech builds software with an AI-supported engineering workflow, where human developers stay responsible for architecture, business logic, testing, and final delivery. Their positioning is direct and practical: AI helps accelerate coding, documentation, and test coverage, while engineers remain in charge of decisions that affect quality and reliability. This model can fit modernization work where old code needs to be reviewed, refactored, documented, or moved forward without turning the project into a long internal backlog.

Mainly, the company focuses on faster delivery of production-ready software, including MVPs, full-stack features, API integrations, and legacy code refactoring. Their process starts with understanding the project intent, then combining engineering oversight with AI-assisted development. For legacy modernization projects, this is a good fit for companies that need focused technical work, quicker iteration, and careful human review before anything reaches production.

Key Highlights:

• AI-assisted software development

• Human-led engineering process

• Legacy code refactoring

• Full-stack development

• API integration

• Documentation support

• Testing and QA review

• Fast delivery model

Services:

• Legacy code refactoring

• Custom software development

• MVP development

• Full-stack feature development

• API integration

• Test coverage

• Technical documentation

• Deployment support

Contacts:

• Website: 21century.tech

• E-mail: [email protected]

9. HCLTech

HCLTech provides enterprise technology services across AI, cloud, engineering, applications, cybersecurity, and digital operations. Legacy modernization fits into their wider application and transformation work, especially for organizations dealing with older systems that limit scalability, integration, or the use of newer technologies. Their approach is shaped around large business environments where modernization usually needs to connect with cloud adoption, AI initiatives, enterprise platforms, and long-term operating models.

Basically, their services are suited to companies that need modernization at scale rather than a small technical fix. HCLTech works across modern applications, enterprise applications, cloud, engineering, and AI-led transformation, which allows them to support both the technical and organizational sides of modernization. For legacy systems, this can include application updates, platform modernization, integration improvements, and preparing systems for more flexible future development.

Key Highlights:

• Enterprise application modernization

• AI and cloud transformation

• Modern application services

• Enterprise application support

• Digital engineering

• Large-scale technology delivery

• Cybersecurity services

• Industry-focused solutions

Services:

• Legacy application modernization

• Modern application development

• Enterprise application services

• Cloud transformation

• AI and GenAI services

• Digital engineering

• Cybersecurity

• Consulting and advisory services

Contacts:

• Website: www.hcltech.com

• Instagram: www.instagram.com/hcltech

• LinkedIn: www.linkedin.com/company/hcl-technologies

• Twitter: x.com/hcltech

• Facebook: www.facebook.com/HCLTechOfficial

• Address: Frankfurter Straße 63-69, 65760 Eschborn

• Phone: +49 6196 7550031

10. Instinctools

Instinctools works with companies that need to move older software into a more stable, flexible, and maintainable state. Their modernization work covers different parts of the software environment, from application architecture and infrastructure to integrations and user interfaces. Instead of focusing only on code updates, they look at how the existing system affects daily operations, security, performance, and future product changes.

Modernization at Instinctools can involve platform migration, code refactoring, cloud migration, containerization, re-engineering, and application customization. AI is also part of their approach, mainly for making old code easier to understand, improving refactoring workflows, and supporting documentation. Their work suits projects where legacy software still carries business value but needs a cleaner technical base to stay useful.

Key Highlights:

• Legacy software modernization

• Platform migration

• Code refactoring

• Cloud migration

• AI-supported modernization

• Application architecture updates

• Interface modernization

• Post-modernization support

Services:

• Legacy software modernization

• Platform migration

• Code refactoring

• Complete re-engineering

• Cloud migration

• Containerization

• Application customization

• Application consulting

Contacts:

• Website: www.instinctools.com

• E-mail: [email protected]

• Instagram: www.instagram.com/instinctools

• LinkedIn: www.linkedin.com/company/instinctoolscompany

• Twitter: x.com/instinctools_EE

• Facebook: www.facebook.com/instinctoolslabs

• Address: Hauptstaetter Str. 89, Stuttgart, D 70178, Germany

• Phone: +4915792517900

11. Zühlke

Zühlke approaches legacy modernization as an engineering and risk-management challenge, especially for organizations with complex systems and limited internal knowledge of older applications. Their work starts by making existing software easier to understand, so teams can see what the system actually does before changing it. AI is used to support this process through architecture analysis, business logic discovery, test generation, and documentation.

Rather than pushing for one large replacement, Zühlke works with staged modernization and iterative delivery. This allows older systems to be improved step by step while keeping releases controlled and reducing downtime risks. Their modernization scope connects software engineering, cloud expertise, data engineering, cybersecurity, and assurance, which is useful for organizations where legacy systems are tied to compliance, operations, and long-term product stability.

Key Highlights:

• AI-powered legacy modernization

• Step-by-step modernization

• Architecture discovery

• Business logic analysis

• Test case generation

• Software engineering expertise

• Cybersecurity focus

• Staged system integration

Services:

• Legacy system modernization

• Application modernization

• AI-supported code analysis

• Architecture analysis

• Test case generation

• Requirements reverse engineering

• Cloud and data engineering

• Cybersecurity consulting

Contacts:

• Website: www.zuehlke.com

• E-mail: [email protected]

• Instagram: www.instagram.com/zuehlkegroup

• LinkedIn: www.linkedin.com/company/zuehlkegroup

• Facebook: www.facebook.com/zuehlke.group

• Address: Düsseldorfer Straße 38, 65760 Eschborn (Frankfurt), Germany

• Phone: +49 6196 777540

12. Siemens

Siemens provides legacy system services for industrial environments that continue to rely on discontinued SIMATIC PCS 7 components. Their focus is not broad software redevelopment, but stable operation of existing plant systems until a planned modernization can be carried out. In this context, legacy support is closely tied to plant availability, technical continuity, and controlled maintenance.

Their services include support for discontinued software components, access to selected legacy products, and validation of Microsoft security patches based on specific system configurations. This makes Siemens relevant for industrial companies that cannot modernize critical systems immediately but still need structured support, predictable maintenance, and a safer path toward future upgrades.

Key Highlights:

• Legacy system services

• Industrial system support

• Support for discontinued SIMATIC PCS 7 components

• Plant operation continuity

• Security patch validation

• Maintenance cost transparency

• Technical documentation access

• Modernization transition support

Services:

• Legacy system support

• Technical support for discontinued components

• Product delivery for selected legacy software

• Microsoft security patch validation

• Patch management support

• Online documentation access

• Industrial cybersecurity services

• Modernization planning support

Contacts:

• Website: www.siemens.com

• E-mail: [email protected]

• Instagram: www.instagram.com/siemens

• LinkedIn: www.linkedin.com/company/siemens

• Twitter: x.com/siemens

• Facebook: www.facebook.com/Siemens

• Address: Oestliche Rheinbrueckenstrasse 50, 76187 Karlsruhe

• Phone: +49 721 667-0

13. Adesso

Adesso works on legacy application modernization with a strong focus on reducing project risk and making older applications easier to evolve. Their scope covers native, hybrid, and outdated web applications, so modernization can start from different technical situations rather than one fixed model. AI-supported analysis is part of the process, helping the team review code, architecture, documentation, and business logic before defining the right path forward.

Their modernization work is structured around assessment, deeper technical review, strategy, and implementation. Depending on the application, Adesso may support refactoring, rebuilding, replatforming, interface modernization, or migration to a more suitable target architecture. Senior engineering oversight remains part of the process, especially where business-critical functions need to be preserved while the application is moved into a cleaner and more maintainable form.

Key Highlights:

• Legacy application modernization

• AI-supported code and architecture analysis

• Technology-agnostic modernization

• Refactoring and rebuild support

• Interface modernization

• Fixed-scope modernization packages

• Human-in-the-loop engineering

• Application testing and documentation

Services:

• Legacy application modernization

• Current state analysis

• Deep technical audit

• Modernization strategy

• Refactoring

• Application rebuild

• Platform migration

• Automated testing and documentation

Contacts:

• Website: www.adesso.de

• E-mail: [email protected]

• Instagram: www.instagram.com/adesso_se

• LinkedIn: www.linkedin.com/company/adesso-se

• Facebook: www.facebook.com/adessoSE

• Address: Adessoplatz 1, 44269 Dortmund

• Phone: +49 231 7000-7000

14. Capgemini

Capgemini supports legacy modernization through CAALM, an AI-assisted approach built around Pega technology. The process starts with understanding the application landscape and identifying where modernization has a clear business case. From there, AI helps analyze application features, extract business rules, create documentation, and prepare older systems for cloud-native transformation.

A notable part of their approach is the verification layer. Documentation and extracted logic are checked against manuals, product documents, and test cases before implementation continues. This gives modernization projects a more controlled structure, especially for enterprises where legacy systems contain important process knowledge that cannot be guessed or casually replaced.

Key Highlights:

• AI-assisted legacy modernization

• Pega-based modernization approach

• Application landscape assessment

• Business rule extraction

• Legacy documentation

• Gap discovery

• Cloud-native transformation

• Automated verification

Services:

• Legacy application modernization

• Application assessment

• Application analysis

• AI-generated documentation

• Business rule extraction

• Gap discovery

• Data migration

• Testing and verification

Contacts:

• Website: www.capgemini.com

• Instagram: www.instagram.com/capgemini

• LinkedIn: www.linkedin.com/company/capgemini

• Facebook: www.facebook.com/Capgemini

• Address: Potsdamer Platz 5, 10785 Berlin, Germany

• Phone: +49 30 88 70 30

15. Fraunhofer IESE

Fraunhofer IESE approaches legacy modernization from a research and engineering perspective. Their work often begins before code changes are planned, with a focus on understanding requirements, business processes, system behavior, and the wider organization around the software. This is useful for legacy systems where documentation is missing, knowledge sits with a small number of people, or the current system has grown over many years.

Modernization support can include as-is analysis, requirements engineering, strategy development, system design, migration planning, and implementation guidance. Besides,they look beyond the technical layer, considering user experience, business models, team structures, and organizational change where these factors affect the success of modernization. Their role is often to help companies make informed decisions before committing to a modernization path.

Key Highlights:

• Legacy system modernization

• Requirements analysis

• As-is system analysis

• Modernization strategy

• Migration planning

• Software and systems engineering

• Organizational modernization support

• Research-based engineering expertise

Services:

• Legacy system analysis

• Requirements engineering

• Modernization strategy

• System and software modernization

• Migration planning

• Architecture support

• UX and business model analysis

• Implementation guidance

Contacts:

• Website: www.fraunhofer.de

• E-mail: [email protected]

• LinkedIn: www.linkedin.com/company/fraunhoferiese

• Facebook: www.facebook.com/FraunhoferIESE

• Address: Fraunhofer-Platz 1, 67663 Kaiserslautern, Germany

• Phone: +49 (0) 631 6800 0

16. Sigma Software

Sigma Software provides legacy modernization and migration services designed to help organizations improve existing systems without taking a one-size-fits-all approach. Every project begins with assessing the current application, its dependencies, business role, and technical limitations. That evaluation becomes the basis for selecting the most appropriate modernization path, whether the goal is gradual improvement, migration, consolidation, or a complete replacement.

Rather than treating modernization as a single migration project, Sigma Software works across different layers of the application landscape. Their capabilities include cloud migration, monolith-to-microservices transformation, software re-engineering, infrastructure upgrades, UI modernization, and data engineering. They also support targeted enhancements that extend the value of existing systems when a full rebuild is unnecessary.

Key Highlights:

• Legacy system assessment

• Modernization strategy development

• Cloud and platform migration

• Monolith to microservices transformation

• Application consolidation

• Software re-engineering

• Data engineering modernization

• UI/UX modernization

Services:

• Legacy modernization consulting

• Technology modernization

• Migration and re-platforming

• Cloud migration

• Application enhancement

• Legacy system replacement

• DevOps modernization

• Data migration and modernization

Contacts:

• Website: sigma.software

• Instagram: www.instagram.com/sigma_software

• LinkedIn: www.linkedin.com/company/68326

• Facebook: www.facebook.com/SIGMASOFTWAREGROUP

• Address: Rosenheimer Str. 143C, 81671 Munchen, Germany

• Phone: +19293802293

17. Softment

Softment focuses on phased legacy system modernization that allows organizations to upgrade applications while maintaining business continuity. Their work covers outdated technology stacks, legacy databases, monolithic architectures, and on-premise environments, with migration plans designed to minimize disruption throughout the transition.

The company combines infrastructure upgrades with application improvements, addressing both technical and operational aspects of modernization. Typical projects include cloud migration, API modernization, database optimization, UI redesign, performance improvements, security enhancements, and CI/CD implementation. Documentation, knowledge transfer, and post-migration support are also included to help teams continue working with the updated system after deployment.

Key Highlights:

• Phased legacy modernization

• Zero-downtime migration strategies

• Cloud infrastructure migration

• Monolith to microservices migration

• API modernization

• Database modernization

• Performance optimization

• Post-migration support

Services:

• Legacy system modernization

• Technology stack migration

• Cloud migration

• Database modernization

• API modernization

• UI/UX modernization

• Security improvements

• CI/CD implementation

Contacts:

• Website: softment.com

• E-mail: [email protected]

• LinkedIn: www.linkedin.com/company/softment

• Twitter: x.com/SOFTMENT_COM

• Address: 1207 Delaware Ave, Suite 3488, Wilmington, DE 19806

18. Intellias

Intellias approaches application modernization as a combination of technical transformation and long-term product evolution. Instead of focusing only on replacing outdated technology, they help organizations evaluate which applications should be retained, migrated, refactored, or rebuilt based on business impact, technical debt, and future priorities.

Their modernization services extend beyond infrastructure upgrades to include cloud readiness assessments, application portfolio rationalization, product strategy, solution discovery, and experience design. Modernization is typically delivered in stages, allowing businesses to introduce incremental improvements while building toward broader platform transformation and continued technology evolution.

Key Highlights:

• Application modernization consulting

• Application portfolio rationalization

• Technical debt assessment

• Cloud readiness evaluation

• Product strategy development

• Experience design

• Solution discovery

• Incremental modernization approach

Services:

• Application modernization

• Technical debt assessment

• Cloud migration planning

• Application rationalization

• Product strategy consulting

• Solution discovery

• Experience design

• Legacy application transformation

Contacts:

• Website: intellias.com

• E-mail: [email protected]

• Instagram: www.instagram.com/intellias_global

• LinkedIn: www.linkedin.com/company/intellias

• Facebook: www.facebook.com/Intellias.GlobalPage

• Address: Wilhelm-Wagenfeld-Str. 28, 80807, 4th floor, Munich, Germany

• Phone: +49 8001800992

Conclusion

Legacy system modernization in Germany is rarely a simple switch from old to new. Most companies need a careful path that protects daily operations, keeps useful business logic, and removes the parts that make every update harder than it should be.

The right provider depends on the state of the system itself. Some projects need deep code analysis and documentation first. Others need cloud migration, new interfaces, better security, or a gradual move away from a monolith. What matters most is not choosing the loudest company, but finding a team that understands why the old system still matters and how to modernize it without creating a new mess.

A good modernization partner should bring structure, patience, and enough technical honesty to say when something should be refactored, rebuilt, or left alone for now. That is often where these projects succeed or fail.