Top Legacy System Modernization Firms

Many core systems still run on COBOL, Visual Basic, old .NET or Java monoliths that few engineers can maintain and that cannot connect to modern tools. Legacy system modernization companies replace or rework them without stopping the business: they assess the codebase, choose between rehosting, refactoring, rearchitecting and rebuilding, then migrate data and users in stages. Companies hire them when vendors end support, when the last developer who knows the system is retiring, when security audits flag unsupported software, or when a new product needs APIs the old system cannot offer.

Compare the firms here on modernizations of your specific technology and on how they keep the old and new systems running side by side during the switch.

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4,482 Companies

List of the Best Legacy System Modernization Agencies

Naissus technologies
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**Experienced Team** For over a decade, we have been developing enterprise software in the **Fintech** sector, establishing intricate systems from scratch. Our team remains robust, boasting an average seniority of over **7 years**. **Ideal Location** We enjoy favorable time overlaps globall
Highlights
$10,000+
Min Project Size
$50-99/hr
Avg Hourly Rate
10-49
Employees
Nis, Rs
Services Provided
40% Custom Web Application Development
25% Mobile App Development (iOS & Android)
20% QA & Software Testing
15% Legacy System Modernization
AI Summary
“Naissus Technologies delivers custom fintech software with a decade of expertise, specializing in event-driven microservices and FIX protocol, leveraging skilled Eastern European teams for quality and efficiency.”
Inventient
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Inventient assists small and medium-sized enterprises in achieving their objectives in the digital space. We focus on areas such as website development, e-commerce, CRM implementation, and automation. Our philosophy centers on a comprehensive approach to digital solutions, aiming to identify opportu
Highlights
$1,000+
Min Project Size
$50-99/hr
Avg Hourly Rate
Saint Kilda East, Victoria, Au
Services Provided
20% Legacy System Modernization
30% E-Commerce Development
50% Cloud Consulting & SI
AI Summary
“Inventient empowers small and medium-sized enterprises with tailored digital solutions, including website development, e-commerce, CRM, and automation to drive growth and operational efficiency.”
Skipfour LLC
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Based in San Francisco, Skipfour employs over 125 associates worldwide. Our US team serves as the primary point of contact for customers, while our offshore team is also available as needed. The US team engages with clients daily to ensure projects stay on course and that any questions or requests a
Highlights
$5,000+
Min Project Size
10-49
Employees
Services Provided
50% Mobile App Development (iOS & Android)
30% Cloud Consulting & SI
20% Legacy System Modernization
AI Summary
“Skipfour LLC delivers high-quality software development and technology solutions, specializing in mobile apps, cloud consulting, and legacy modernization, serving diverse industries with global, client-focused expertise.”
REEA Global
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AI-Powered Software Development for Companies Backed by Private Equity. A technology partner that recognizes the investment duration, strategies for value enhancement, and the urgency for swift results, all while reducing risk. We simplify the process for mid-market firms to comprehend, implement, a
Highlights
$10,000+
Min Project Size
$100-149/hr
Avg Hourly Rate
50-249
Employees
Baltimore, Maryland, Us
Services Provided+7 Services
7% Custom Web Application Development
5% Mobile App Development (iOS & Android)
4% E-Commerce Development
18% Legacy System Modernization
AI Summary
“REEA Global partners with private equity-backed mid-market firms to deliver AI-powered software solutions, enhancing value through automation, integration, cloud transformation, and legacy modernization with reduced risk.”
Ready4S
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We are a custom software and system integration firm with a decade of market experience, positioned as your nearshore technical partner. Located in Krakow, Poland—often referred to as the Polish "Silicon Valley"—we’re passionate about innovative technologies that yield exceptional results and enhanc
Highlights
$50,000+
Min Project Size
$50-99/hr
Avg Hourly Rate
50-249
Employees
Krakow, Lesser Poland, Pl
Services Provided+1 Services
35% Custom Web Application Development
15% Legacy System Modernization
25% Product UX Strategy
18% Interaction Design
AI Summary
“Ready4S is a Krakow-based custom software and system integration firm with a decade of experience, delivering comprehensive solutions including development, QA, and DevSecOps for diverse industries.”
blueriver
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At Blueriver, we develop enterprise solutions that propel the most impactful companies globally. By updating outdated applications, crafting sophisticated digital experiences, and designing enterprise platforms, we provide solutions that enhance the lives of both employees and customers.
Highlights
10-49
Employees
Sacramento, California, Us
Services Provided+1 Services
23% Custom Web Application Development
20% Legacy System Modernization
7% CMS Development & Customization
30% Product UX Strategy
AI Summary
“Blueriver delivers advanced enterprise solutions by modernizing applications, designing digital experiences, and building platforms that improve operational efficiency and user engagement worldwide.”
Bit Complete
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Bit Complete is a Toronto-based software firm. We develop products and offer consulting services to a range of early and mid-stage startups, assisting them in establishing their teams, products, and infrastructure. Our goal is to expedite product development and foster an environment conducive to ma
Highlights
$10,000+
Min Project Size
$100-149/hr
Avg Hourly Rate
10-49
Employees
Services Provided
50% Custom Web Application Development
35% Mobile App Development (iOS & Android)
15% Legacy System Modernization
AI Summary
“Bit Complete is a Toronto-based software company providing development products and consulting to early and mid-stage startups, accelerating product creation and enabling sustainable technical decisions.”
Koderly
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Koderly is a custom software development and IT services firm based in Manchester, boasting over 22 years of experience in delivering innovative technology solutions for top-tier brands. Our expertise includes software development, database administration and support, travel technology, and test man
Highlights
$5,000+
Min Project Size
10-49
Employees
Manchester, England, Gb
Services Provided
14% Legacy System Modernization
20% Custom Web Application Development
33% Other IT Consulting and SI
33% Managed IT Services
AI Summary
“Koderly, based in Manchester with 22+ years' experience, specializes in custom software development, IT services, database support, travel technology, and test management for leading brands.”
Webhouse
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Webhouse is a Sydney-based custom software development firm. We specialize in creating tailored software, web applications, mobile apps, and business platforms, managing the entire process from initial scoping and discovery to design, development, integrations, and ongoing support. Our clients inclu
Highlights
$10,000+
Min Project Size
$100-149/hr
Avg Hourly Rate
2-9
Employees
Parramatta, New South Wales, Au
Services Provided+1 Services
30% Custom Web Application Development
25% Mobile App Development (iOS & Android)
20% API Development & Integration
15% Legacy System Modernization
AI Summary
“Webhouse, based in Sydney, delivers custom software, web and mobile applications, and business platforms for Australian SMEs, integrating advanced technologies and providing long-term development partnerships.”
On Tap
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On Tap is a global eCommerce agency with offices in various countries. Established in 2007, it was among the first agencies to provide development services for Magento and Adobe Commerce. Over the years, we have broadened our skill set to encompass platforms like Shopify, BigCommerce, WooCommerce, a
Highlights
$10,000+
Min Project Size
$50-99/hr
Avg Hourly Rate
250-999
Employees
London, England, Gb
Services Provided
20% Legacy System Modernization
30% E-Commerce Development
50% CRM Consulting and SI
AI Summary
“On Tap is a global eCommerce agency offering customizable solutions including development, integration, migration, marketing, consulting, and training across platforms like Magento, Shopify, and more.”

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Top Legacy System Modernization Firms

List of the Best Legacy System Modernization Agencies

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