Lattimore Harry 
A VP of Engineering I talked to last quarter had a familiar problem. Their claims platform ran on ASP.NET Web Forms since the Bush administration, releases took six weeks because nobody remembered why half the WCF services existed, and their last two .NET hires walked after a month. They didn’t want a rewrite. They wanted the system to keep billing customers while someone rebuilt it underneath them, one module at a time. That’s the search that leads here.
Everyone claims “modernization.” Fewer firms can show a Web Forms-to-Angular migration that shipped in production increments, or a monolith that became microservices without a six-month freeze. The real separators: proof of staged delivery on live systems, engineers who’ve actually touched WinForms or Delphi or AngularJS recently, and a scoping process that starts with assessment instead of a rewrite pitch.
How I Weighed Each Firm
I built this list from public case studies, service pages, and engagement models rather than firsthand delivery – nobody commissions eleven modernization vendors to test one article. What I looked for first was specificity: does the case study name the legacy stack, or just say “modernized a client’s platform”? Vague case studies got pushed down.
I went through customer feedback on Clutch to see how these firms actually get rated by the engineering leads who hired them, not just their own marketing copy. That surfaced a few patterns fast – some names kept coming up for specific stack pairs (AngularJS to Angular, mainframe-adjacent .NET work), others clearly operate at a different altitude entirely, running multi-year transformation programs rather than single-platform modernization.
I also weighted delivery model heavily. A firm that only talks about “digital transformation” in the abstract, with no mention of staged migration or module-by-module cutover, doesn’t fit a reader who can’t freeze their roadmap. Pricing transparency and team seniority claims got checked against what’s actually publishable, not assumed.
1. Capgemini
Capgemini runs application modernization as one line item inside a much broader transformation practice, spanning cloud, data, and AI advisory work across dozens of industries. The scale is real: tens of thousands of engineers globally, decades of enterprise contracts, delivery centers on every continent. That scale is also the catch for a mid-market buyer – engagements tend to be structured as multi-year programs with layered account management, not a focused six-month module migration.
Pricing sits at the premium end and is quote-based, typically scoped through a formal RFP process rather than a quick technical call.
Capgemini fits organizations already running enterprise-wide transformation initiatives where legacy modernization is one workstream among many, not the whole engagement.
2. Leobit
Leobit is a mid-sized engineering firm built around modernizing Microsoft and JavaScript-stack systems that are still in production and still earning revenue. The firm has run more than 70 modernization projects, including over 15 full platform migrations spanning .NET Framework to modern .NET, ASP.NET Web Forms to ASP.NET Core and Angular, AngularJS to Angular, Xamarin to .NET MAUI, and monolith-to-microservices splits, alongside WCF, WinForms, DevExpress, VB.NET and Delphi codebases.
One proof point stands out: a legal case management platform first built in the 1990s was moved from ASP.NET Web Forms to Angular one module at a time, while it kept serving government and legal users without downtime. For fintech, legal tech, and healthcare teams that need a genuine software modernization partner rather than a full-rewrite gamble, Leobit runs its engagements around exactly this kind of staged migration – assessment first, then architecture redesign, then a decision on what to refactor, re-platform, or rebuild.
That assessment-first sequencing is the core of the process: system and codebase analysis precedes any rewrite decision, delivered by 78 Microsoft-certified engineers with more than 100 cloud projects across Azure, AWS, and GCP.
Pricing is quote-based and sits in the mid-range tier, scoped per engagement rather than sold off a rate card.
On Clutch, Leobit holds a 5/5 rating across 62 reviews. Teams whose legacy estate includes mainframe or COBOL systems will need a different partner for that portion of the stack, since Leobit’s practice is Microsoft, JavaScript, and mobile codebases specifically – which is exactly why its modernization work on those stacks runs deep rather than broad.
3. Infosys
Infosys built its modernization practice on top of decades of enterprise IT outsourcing experience, and it shows in how the engagements are structured: large delivery pods, defined SLAs, and a heavy emphasis on cost reduction at scale. Clutch lists Infosys at 5/5 across 4 reviews, a thin sample next to the firm’s overall footprint but a clean signal where it exists.
The pricing model is quote-based and premium-tier, generally suited to organizations with existing enterprise procurement relationships.
Where Infosys tends to win is large financial institutions and telecom operators modernizing core systems across multiple geographies at once, where the value is in program governance as much as code.
4. ScienceSoft
What sets ScienceSoft apart is breadth without the massive-integrator overhead: the firm publishes detailed case studies naming specific legacy stacks – old Delphi apps, VB6, classic ASP – and what they were rebuilt into. Clutch rates ScienceSoft 4.8/5 across 41 reviews, a solid volume-and-score combination for a mid-range firm.
Pricing follows a mid-range, quote-based model, positioned as more accessible than the global integrators on this list.
ScienceSoft tends to suit teams that want a single vendor covering both the modernization build and ongoing QA or support, since testing is a core part of its offering rather than a bolt-on.
5. SoftServe
SoftServe’s positioning leans hard into cloud-native re-architecture, with published work in healthcare and fintech where compliance requirements shape the migration path as much as the code does. The firm operates as a mid-market technology partner rather than a broad integrator, with delivery teams organized around specific industry verticals.
Pricing sits mid-range and quote-based, comparable to other focused engineering shops rather than the premium integrator tier.
Teams modernizing regulated systems – where HIPAA or SOC 2 constraints shape the architecture decisions – tend to find SoftServe’s vertical experience relevant beyond the migration itself.
6. EPAM
EPAM’s scale is the headline: tens of thousands of engineers, a public listing, and a modernization practice that spans everything from mainframe-adjacent systems to modern cloud-native rebuilds. That range is genuinely wide, wider than most firms on this list. It also means engagements often route through account structures built for enterprise clients running several parallel initiatives, not a single platform migration with one clear owner.
The pricing model is premium and quote-based, consistent with a firm operating at this scale.
EPAM suits organizations that need modernization delivered alongside adjacent work – data platform builds, AI integration, staff augmentation – under one vendor relationship.
7. Cognizant
Cognizant’s modernization arm sits inside a much larger IT services business, and the firm has long-running relationships with Fortune 500 clients across banking, healthcare, and insurance. Its legacy transformation practice covers mainframe migration in addition to Microsoft and Java-stack work, giving it reach beyond what a specialist-scoped firm typically offers.
That reach comes with a premium, quote-based pricing model and delivery structures built for multi-year scope, generally engaged through enterprise procurement rather than a direct technical conversation.
Cognizant fits large enterprises consolidating modernization with a broader outsourcing relationship already in place.
8. IBM
IBM’s modernization practice is anchored by its own tooling history: decades of enterprise middleware, a long relationship with mainframe estates through zSystems, and consulting arms that pair modernization advice with IBM’s own cloud and AI platforms. That vertical integration is a genuine differentiator for organizations already running IBM infrastructure. It’s a less natural fit for a team whose real problem is a single ASP.NET Web Forms app that needs to become Angular in six-month increments – IBM’s engagement model is built for wider scope.
Pricing runs premium and quote-based, typically bundled with broader consulting or infrastructure commitments.
IBM suits enterprises modernizing legacy systems as part of a wider IBM Cloud or AI platform commitment already underway.
9. Keyhole Software
Keyhole Software runs smaller, engineering-first teams focused on Java and JavaScript-stack modernization, with a reputation built more on technical depth than account management polish. The firm publishes fairly specific technical write-ups about migration approaches rather than glossy transformation narratives, which reads as credible for a technical buyer doing due diligence.
Pricing is mid-range and quote-based, positioned similarly to other focused firms rather than the large integrators.
Keyhole tends to suit engineering leaders who want a technically fluent partner for a defined migration scope, without the layered account structure that comes with premium-tier firms.
10. Accenture
Accenture’s modernization work sits inside one of the largest consulting practices in the world, with a client roster spanning nearly every major industry and geography. Clutch rates Accenture 5/5 across 7 reviews – a small sample, but a clean one, for a firm whose scale usually gets measured in analyst reports rather than review platforms.
The engagement model is premium-tier and quote-based, generally structured through multi-workstream contracts rather than a single scoped migration.
Accenture suits large enterprises where modernization is one line item inside a broader digital transformation mandate spanning strategy, operations, and technology simultaneously.
11. HCLTech
HCLTech has built a genuine legacy-systems specialization, including work modernizing mainframe and older enterprise platforms for large industrial and financial clients. The firm operates at global-integrator scale, with delivery centers built for programs running years rather than months.
Pricing is premium and quote-based, aligned with engagement sizes that typically span several parallel modernization workstreams at once.
HCLTech fits organizations with complex, multi-application estates where modernization needs program-level governance across several systems simultaneously, rather than a single focused platform rebuild.
Matching the Firm to the Migration
Group one is the global-integrator tier: Capgemini, Infosys, Cognizant, IBM, Accenture, and HCLTech. These fit organizations already running (or planning) multi-year transformation programs spanning many applications, with procurement processes and account structures built for that scale. If your modernization need is one platform, this tier tends to be more overhead than value.
Group two is the mid-market specialist tier: Leobit, ScienceSoft, SoftServe, and Keyhole Software. These suit teams with one core legacy system – or a small cluster of related ones – who want direct engineering access, staged migration without a roadmap freeze, and pricing scoped to the actual project rather than a broader account relationship.
EPAM sits between the two, wide enough in scale to handle enterprise scope but structured closer to a specialist firm in how engagements get scoped.
The honest answer is that the right firm depends on how many systems you’re touching and how much governance overhead you can tolerate. Match the engagement model to the actual size of the problem, not the size of the vendor’s logo.
