Best 7 Mainframe Modernization Companies for Cloud Migration (AWS, Azure, GCP)

Mainframes still handle the world’s most important data, but keeping them is becoming too expensive. The biggest problem isn’t just the hardware; it’s that new developers don’t want to work with 50-year-old code. Because of high fees and a lack of experts, most businesses are now moving their systems to the cloud.

Instead of trying to change everything at once, the best companies move one piece at a time. This keeps the business running while the technology gets an upgrade. Here are the top mainframe modernization companies helping businesses move to AWS, Azure, and GCP today.

1. Corsac Technologies

• Location: United States / Remote
• Established: 2007
• Team Size: 50 – 249 specialists
• Specialization: High-compliance legacy stacks (FinTech, Healthcare)

Corsac Technologies helps teams move past legacy mainframes that slow development. When a codebase feels too risky to change, progress stalls. Corsac addresses this by working directly in existing Git repositories and CI/CD pipelines. They migrate older stacks like Delphi or FoxPro into modern .NET Core environments. In regulated areas like healthcare, they include HIPAA and SOC2 compliance in the architecture, reducing technical debt at its source.

2. Refactorly App

• Location: United States / Remote
• Established: 2014
• Team Size: 50 – 100 specialists
• Specialization: AI-driven logic extraction and agentic refactoring

Refactorly App provides an engineering framework to automate and de-risk mainframe cloud migrations. Manual rewrites carry heavy risks. Refactorly changes the math using a Retrieval-Augmented Generation (RAG) architecture paired with a Multi-Agent Swarm. This setup treats legacy code as a dataset. An Archaeologist Agent scans for security gaps. AI then drafts new React or Node.js logic. A strict Circuit Breaker monitors the launch. If errors hit 1%, traffic instantly reverts to the old mainframe.

3. Astadia (part of Amdocs)

• Location: Jacksonville, FL, USA
• Established: 1992
• Team Size: 200 – 500 specialists
• Specialization: End-to-end migration and DevOps integration

Astadia is a veteran who has moved thousands of applications off the mainframe. Now part of Amdocs, they offer a full roadmap from planning to cloud testing. They use a mix of rehosting and refactoring depending on what the business needs. Their experience is useful for massive projects that involve moving many connected systems at the same time. They add modern DevOps practices so you do not end up with old logic in a new cloud wrapper.

4. TmaxSoft (OpenFrame)

• Location: Chicago, IL / Seoul, South Korea
• Established: 1997
• Team Size: 1,000+ employees
• Specialization: Mainframe rehosting and database updates

TmaxSoft is known for OpenFrame, which lets mainframe apps run in the cloud without changing the original code. This is called “rehosting.” It is a fast path for companies that need to get off expensive hardware quickly but are not ready for a full rewrite. OpenFrame supports COBOL and JCL, making the move to an Azure or AWS virtual machine much faster. This approach buys the company time to plan a deeper update later while lowering costs immediately.

5. CloudFrame

• Location: Princeton, NJ, USA
• Established: 2016
• Team Size: 50 – 150 specialists
• Specialization: COBOL-to-Java cross-compilation and MIPS reduction

CloudFrame helps you save money even before you finish the move to the cloud. Their software turns COBOL into Java, allowing it to run on cheaper Linux servers while keeping data on the mainframe. This lowers your MIPS bill right away. For those moving to Azure or GCP, CloudFrame lets you shift workloads gradually. This reduces the risk of one large cutover day and provides a clear path for organizations that need early cost savings.

6. Advanced (Modern Systems)

• Location: Phoenix, AZ, USA
• Established: 1983
• Team Size: 250 – 500 specialists
• Specialization: Automated refactoring and application assessments

Advanced modernizes legacy systems (like COBOL or Natural Adabas) into Java or C#, using structured automation suited for large government and banking projects. They stand out for strong assessment tools that map what can be migrated, helping teams plan accurate budgets and timelines.

7. Blu Age (part of AWS)

• Location: Paris, France / Global
• Established: 2005
• Team Size: 500+ specialists
• Specialization: Mainframe-to-AWS automated transformation

Now part of Amazon, Blu Age powers AWS Mainframe Modernization by converting legacy applications into Java microservices running on AWS. It automates code and data transformation, enabling fast migration into the AWS ecosystem and is often chosen by companies already committed to Amazon cloud.

Practical Insights

In 2026, modernization isn’t just about updating systems  –  it’s about moving past outdated software and growing the business. The cloud helps you move faster, but it’s not just an IT task. It’s a shift in how the business works.

Companies work in different ways  –  some move fast, others go deeper and rebuild systems from the ground up. What works best depends on what you’re trying to achieve.

The companies that win treat their software as an asset. With the right partner, legacy systems and mainframe modernization stop being a burden and start driving growth.