Modernizing decades-old software is no longer an IT cleanup exercise; it’s a board-level priority. Technical debt now consumes 20-40% of the typical technology estate, and research published in 2025 found the average global enterprise burns through more than $370 million each year just keeping creaky systems alive. Digital transformation leaders are therefore hunting for partners that can move fast, honor existing business logic, and pave a path to cloud-native agility.

Why This Matters Right Now

Running a digital business on brittle code slows releases, soaks up talent, and creates security gaps. The survey of 500 IT executives in 2025 reported that 95% already rely on external help to chip away at legacy complexity, yet only 21% feel they are ahead of the curve. The gap between ambition and execution is huge, which is why choosing the right modernization vendor may determine whether your next strategic roadmap ships on time or stalls for another budget cycle.

What follows is a focused, practitioner-oriented look at five vendors that consistently surface in enterprise shortlists. Direct product pitches are omitted; instead, we examine where each shines, how they de-risk transformation, and what type of enterprise profile tends to benefit most. Although toolchains and cloud platforms matter, the most successful legacy software modernization services unite assessment, architecture, and iterative delivery under one outcome contract.

Selection Principles

Any list of “top IT service companies for legacy modernization” is subjective, so it helps to reveal the criteria used here:

• Global or multi-region delivery capable of handling complex estates (mainframe, mid-tier, custom code).
• Demonstrated experience converting monoliths to modular or microservice architectures without business disruption.
• Transparent pricing or outcome-based models that align vendor incentives with client KPIs.
• Well-rated by independent analysts or platforms (e.g., Clutch, Gartner peer reviews).
• Active investment in AI-enabled code analysis, automated test generation, or DevSecOps pipelines to accelerate change.

With that frame in mind, let’s meet the five firms.

DXC Technology

DXC was born in 2017 from CSC and HPE Enterprise Services. The merger created a Fortune 500 heavyweight with roughly 125,000 employees and a modernization factory mindset.

Why enterprises shortlist DXC

• Mainframe calorie burner. DXC’s Modernization-as-a-Service wraps assessment, code conversion, and platform cut-over into a single commercial line item. Pricing often follows a line-of-code or fixed-price model, so CFOs know the ceiling cost before kicking off.
• AI inside. The company’s proprietary analyzers scan COBOL, PL/1, or RPG in minutes, highlight dead code, auto-document business rules, and even suggest target microservices. Engineers then validate changes rather than hand-rewrite everything, trimming timelines by months.
• Risk governance. Few vendors can match DXC’s ISO-laced processes, global data-sovereignty options, and cyber-resilience playbooks – a key reason public-sector agencies choose them for sensitive workloads.

Best-fit scenarios

Global banks, insurers, and governments that still run mission-critical workloads on IBM Z or Unisys kit. If you need to refactor millions of lines, run parallel ops, and flip the switch country by country, DXC owns that playbook.

Caution flags

Some customers feel DXC’s size makes it less nimble for sub-$5 million engagements. If you’re a mid-market firm after rapid sprints, you may favor a boutique.

Radixweb

Founded in 2000 in Ahmedabad, Radixweb has delivered 4,200+ projects across 25 countries, but its sweet spot is phased, UX-first re-platforming.

Why enterprises shortlist Radixweb

• Low-risk pilots. Instead of scoping a multi-year overhaul, Radixweb often starts with a two-to-four-month slice: one domain, one API cluster, or a single customer journey. That proves value quickly and lets sponsors secure an incremental budget instead of a big-bang ask.
• Automation-first. The firm leans on in-house scaffolding to generate container templates, CI/CD pipelines, and infrastructure-as-code in the first sprint. Clients inherit tested blueprints they can replicate across business units.
• UX as a north star. Legacy transformations sometimes forget the end user. Radixweb bakes UI/UX into its governance gates, ensuring what comes out is not just technically fresh but measurably easier for staff or customers to use.

Best-fit scenarios

ISVs, software-driven mid-caps, and enterprise product teams that want to modernize modules while shipping new features every quarter. If internal designers care as much about pixel polish as refactoring, Radixweb feels familiar.

Caution flags

Radixweb’s India-centric delivery keeps rates attractive but can raise time-zone juggling for U.S. or EU teams that need real-time workshops. They mitigate via near-shore leads, yet it’s a consideration.

Devox Software

Devox, founded in 2018, may be the youngest here, but its 92% NPS and 5-star Clutch score tell a story. The firm blends legacy refactor work with financial transparency systems that track cloud costs, making the business case visible sprint by sprint.

Why enterprises shortlist Devox

• AI-powered mapping. Devox tools reverse-engineer architecture diagrams, database schemas, and service interactions, then overlay cost/performance metrics. Sponsors instantly see which modules are money pits.
• FinOps alignment. As code moves to Azure, AWS, or GCP, Devox configures automated budgets, right-sizing, and cost alerts as part of the definition of done. You don’t just modernize; you control run costs from day one.
• Multi-stack versatility. Teams jump from .NET Core to Node to Go without breaking cadence, which is handy in polyglot estates.

Best-fit scenarios

Digital-native enterprises that already report cloud spend to the board and need every sprint to link back to dollars saved or revenue enabled.

Caution flags

Devox thrives on collaborative workshops and tight feedback loops. If your culture leans toward command-and-control with heavyweight change tickets, productivity can dip.

Facile Technolab

Operating since 2016, India-based Facile Technolab often enters as an extension of the client’s engineering team rather than a classic consulting arm.

Why enterprises shortlist Facile

• Elastic squads. Need a React+Node pod this quarter and a .NET+C++ pod next? Facile ramps up specialist talent in weeks, keeping internal velocity high while legacy components are re-architected.
• API-led modernization. The firm’s playbook usually starts with wrapping old logic in clean REST or GraphQL services. That buys breathing room before deeper code surgery and lets new mobile or web apps ship early.
• Friendly governance. Clients praise Facile’s transparent Jira boards, demo cadence, and willingness to co-create Definition of Ready/Done.

Best-fit scenarios

Product companies or IT departments that already own architectural decisions but need horsepower to chew through backlogs and modernization epics.

Caution flags

Facile is perfect for slice-by-slice rejuvenation but may not own an entire transformation office spanning change management, data migration, and regulatory approvals. For those, pair them with a strategy consultancy.

Celerik

Headquartered in Colombia with hubs in Austin and London, Celerik has delivered digital products since 2008 and shines when legacy systems require a cutting-edge UI/UX front end plus integration to modern cloud services.

Why enterprises shortlist Celerik

• Design-plus-code DNA. Their front-end studio can drop 3D-enabled React apps that sit on top of old transaction kernels, improving user satisfaction before the heavy lifting even kicks off.
• Time-zone advantage. U.S. and EU executives get near-real-time collaboration without red-eye calls, a subtle yet powerful accelerant for feedback-rich modernization.
• Cloud-native tailoring. Celerik often leapfrogs by implementing event-driven patterns (Kafka, AWS SNS/SQS) to decouple services. That reduces cascade failures that plague monoliths.

Best-fit scenarios

Energy, media, or logistics players that want customer-facing innovation (dashboards, digital twins) while retiring heritage stacks behind the scenes.

Caution flags

Celerik’s teams skew full-stack JavaScript and cloud; if your legacy estate is deep SAP ABAP or MUMPS, another vendor may offer stronger muscle.

Using the Shortlist

You now know five distinct flavors of legacy software modernization companies. Here’s a pragmatic way to narrow further:

Step 1 – Map constraints

Document core pain points: is it mainframe expense, release velocity, talent shortage, or user experience? Weigh them.

Step 2 – Align vendor DNA

Match those weights to vendor strengths above. For example, if a predictable large-scale COBOL conversion tops your list, DXC rates high. If “show me new UX next quarter” dominates, Celerik or Radixweb takes the lead.

Step 3 – Run a proof of value, not a beauty contest

Invite your top two candidates to tackle the same mini-module – perhaps a reporting service with gnarly data transformations. Observe not just technical output but communication, documentation, and cost tracking.

Step 4 – Lock in outcome metrics

Whatever partner you choose, bake in KPIs that link to enterprise strategy: release lead time, defect escape rate, cloud cost per transaction, or revenue from new digital channels. Then revisit quarterly.

Emerging trends to watch

Automation and AI will soon rewrite more code than human engineers. Gartner predicts increasing use of AI code assistants by software engineers, with adoption expected to reach around 75% by 2028, reflecting the broader integration of AI into development workflows. Vendors on our list are already embedding such capabilities, which means selection criteria should now include how well a partner operationalizes AI governance, traceability, and security.

Equally, commercial models are shifting. Leaders increasingly expect consumption- or outcome-based pricing. As the HFS-Publicis Sapient “Smash Through Tech Debt” study notes, four in five enterprises want to pivot away from headcount rate cards to AI-powered services. Among the five companies profiled, DXC and Devox are already public about transaction or FinOps-anchored pricing pathways.

Closing thoughts

Technical debt has morphed from a nagging engineering concern into a direct threat to revenue, security, and customer experience. The good news: a mature ecosystem of vendors now exists, each with distinct strengths, pricing guardrails, and cultural fits. Study your own constraints, prototype fast, and choose a partner that not only refactors code but also boosts business agility. Do that, and next year’s budget conversation can shift from “keeping the lights on” to “shipping the next big idea.”