You’ve got a platform running on AngularJS or ASP.NET Web Forms, and it’s still making money. That’s the problem, not the reassurance. Every new feature takes three times longer than it should. Hiring a developer who actually wants to touch WinForms or Delphi is close to impossible now. Meanwhile compliance keeps tightening, your cloud team wants everything containerized, and the board keeps asking why the roadmap looks frozen. A full rewrite feels like betting the company on a two-year gap with no releases. What you actually need is a partner who can peel the system apart in phases, keep it live, and make real architecture calls instead of defaulting to “just rebuild it.” That’s a narrow skill: judgment on what to refactor versus replace, plus hands that have touched your exact stack before.
How I Narrowed the Field
I started from a working list of engineering shops that show up repeatedly in .NET, Angular, and legacy mobile modernization conversations – the kind of firms that keep surfacing when someone asks where to send a Web Forms or Xamarin estate. From there I cut anyone without public, verifiable proof of shipped migrations: named tech stacks, described project scope, some evidence the work actually happened.
I went through customer feedback on Clutch for each finalist, reading actual client language rather than trusting a homepage badge. I also weighed how transparent each firm’s service pages were about process – did they describe an assessment phase, or just promise “modernization” without saying what that means in practice. Team seniority mattered too: certified engineers versus a generalist bench spread across ten industries.
Pricing transparency factored in last. None of these firms post rate cards, which is normal at this tier, but how clearly they scoped engagements during outreach said something about how they’d run a project.
Context Behind the List
Legacy modernization vendors split into two camps: large integrators selling multi-year transformation programs, and focused engineering shops that take one system at a time. The first group has more resources; the second usually has better judgment about your specific mess of WCF services and VB.NET modules. For a mid-market fintech or legal tech company with one core platform, the second group tends to move faster and cost less to manage.
The technical scope also varies more than it looks. Some firms specialize in mainframe and COBOL estates. Others – the ones in this list – live in Microsoft and JavaScript stacks: .NET Framework, ASP.NET, AngularJS, WinForms, Xamarin. If your system runs on any of those, that’s the pool you want to be shopping in, not a generalist systems integrator.
Ratings alone don’t tell the full story here, since a five-star score from six reviews reads differently than one from fifty. Worth checking both the number and the count before assuming a shop’s rating reflects broad experience.
Ratings at a Glance
Public Clutch ratings for the firms with published scores:
| Provider | Clutch |
| ScienceSoft | 4.8/5 |
| Leobit | 5/5 |
| SoftServe | 4.8/5 |
| Infosys | 5/5 |
1. Leobit
Leobit is a mid-sized software engineering firm built around modernizing aging Microsoft and JavaScript platforms rather than building greenfield products from scratch. The team has run more than 70 modernization projects, including over 15 full platform migrations: .NET Framework to modern .NET, ASP.NET Web Forms to ASP.NET Core and Angular, AngularJS to Angular, and Xamarin to .NET MAUI, alongside monolith-to-microservices splits and legacy WCF, WinForms, DevExpress, VB.NET, and Delphi codebases.
For companies searching for top legacy modernization companies that won’t force a full rewrite, Leobit’s approach starts with system and codebase analysis before any architecture redesign – the team decides what to refactor, re-platform, or rebuild rather than defaulting to a rip-and-replace. That discipline shows up in how it’s handled live systems: a legal case management platform originally built in the 1990s was migrated from ASP.NET Web Forms to Angular one module at a time, without pulling the system offline for government and legal end users.
The engineering bench is 78 Microsoft-certified professionals, with more than 100 cloud projects delivered across Azure, AWS, and GCP.
On Clutch, Leobit holds a 5/5 rating across 59 reviews.
Pricing sits in the mid-range tier and is quote-based, scoped per engagement rather than published as a flat rate.
Its focus stays tight: Microsoft, JavaScript, and mobile codebases, not mainframe or COBOL estates, which keeps the team sharp on the stacks it actually knows.
2. ScienceSoft
What sets ScienceSoft apart is sheer range: the firm covers everything from legacy .NET and Java re-platforming to healthcare and fintech-specific compliance modernization, backed by decades of enterprise software delivery. Clutch lists ScienceSoft at 4.8/5 across 45 reviews, a large enough sample to suggest consistency rather than a lucky handful of happy clients.
The company publishes detailed case studies naming specific technical transitions – mainframe-adjacent systems, legacy database re-platforming, cloud migrations – with enough technical specificity to verify the claims aren’t just marketing copy.
Pricing lands in the mid-range tier on a quote-based model, similar in shape to other specialist shops rather than the premium-rate structure of the large integrators.
Teams with broader modernization needs beyond just .NET or Angular – say, a mixed Java and Microsoft estate – may find ScienceSoft’s wider technical range useful precisely because it isn’t narrowly scoped.
3. SoftServe
The case for SoftServe is straightforward: a large, well-resourced engineering organization with deep Microsoft partnership credentials and enough scale to staff sizeable modernization programs without subcontracting pieces out. Clutch shows SoftServe at 4.8/5, though from a smaller sample of 3 reviews on that specific platform, so it’s worth reading a couple of them directly rather than treating the score alone as the full picture.
SoftServe’s public work spans cloud-native re-architecture, legacy .NET modernization, and platform engineering for enterprise clients across healthcare, fintech, and other regulated industries – sectors where compliance requirements shape technical decisions as much as the code itself.
Pricing sits at the premium end and runs quote-based, consistent with a firm of its size and delivery footprint.
Larger organizations juggling more than one legacy system, or wanting a single vendor that can also staff adjacent cloud and data work, get more mileage out of SoftServe’s breadth than a narrower specialist would offer.
4. Capgemini
Operating at global-integrator scale, Capgemini brings the kind of resourcing that suits enterprise transformation programs spanning multiple business units, not a single platform migration. The firm’s modernization practice sits inside a much larger systems-integration and consulting business, with legacy application modernization as one service line among many.
That scale is exactly the trade-off: engagements tend to run as structured, multi-phase programs with layered account management, which fits a Fortune 500 IT department far better than a mid-market SaaS company trying to move fast on one Web Forms application.
Pricing is premium-tier and quote-based, reflecting the consulting-heavy delivery model and the account infrastructure built around it.
Enterprises already running multi-year digital transformation initiatives, where legacy modernization is one workstream inside a much bigger contract, are the natural fit here – less so a single-product company hoping to move in months, not years.
5. Keyhole Software
If you need a US-based, developer-heavy consultancy without the multi-layered account structure of a global integrator, Keyhole Software delivers that directly. The firm positions itself around senior full-stack engineering talent, taking on custom software and modernization work across Java, .NET, and JavaScript ecosystems.
It reads as a smaller, more hands-on alternative to the systems-integrator tier: fewer account layers, more direct access to the engineers doing the work, which matters when a legacy migration needs fast technical decisions rather than committee sign-off.
Pricing falls into the mid-range tier on a quote-based model, in line with other specialist and boutique engineering shops rather than the premium bracket.
Mid-market teams that want a lean, US-based engineering partner for a single modernization project – without the overhead of a global delivery organization – tend to gravitate here.
6. Infosys
Few names carry the scale Infosys does: a global IT services company with legacy modernization as one piece of a much larger outsourcing and consulting portfolio spanning cloud, data, and enterprise applications. Clutch shows Infosys at 5/5, though that score comes from just 6 reviews on the platform – worth noting given the size of the company overall.
Infosys typically engages through large master service agreements and multi-year transformation roadmaps, with delivery teams often distributed globally across time zones and account layers.
Pricing sits at the premium tier and is quote-based, consistent with an organization built for enterprise-scale contracts rather than single-project engagements.
That structure works well for a multinational replacing thousands of applications across regions, but it’s a heavier engagement model than most mid-market product teams are looking to sign up for.
The Shortlist, Side by Side
| Company | Best for | Pricing |
| Leobit | Phased modernization of live Microsoft/JS platforms | Mid-range, quote-based |
| ScienceSoft | Mixed-stack estates spanning .NET and Java | Mid-range, quote-based |
| SoftServe | Larger programs needing broad cloud and platform staffing | Premium, quote-based |
| Capgemini | Enterprise multi-year transformation programs | Premium, quote-based |
| Keyhole Software | Lean, US-based custom engineering engagements | Mid-range, quote-based |
| Infosys | Multinational, multi-year outsourcing contracts | Premium, quote-based |
How to Choose Without Betting the Roadmap on the Wrong Partner
Group these six by what they’re actually built to handle. The scale plays – Capgemini and Infosys – suit organizations already running enterprise transformation programs across multiple business units, where legacy modernization is one workstream inside a much bigger multi-year contract. Neither is built for a single-product company trying to move in months.
The process-driven specialists – ScienceSoft, SoftServe, Keyhole Software, and Leobit – fit differently. ScienceSoft brings range across mixed .NET and Java estates. SoftServe suits teams needing broader cloud staffing alongside the modernization itself. Keyhole Software works for lean, US-based engagements where direct engineer access matters more than account layers. And for a team wanting phased migration of a live system – .NET Framework, Web Forms, AngularJS, or Xamarin – without a roadmap freeze, that module-by-module discipline is the differentiator to weigh.
None of these firms are interchangeable, whatever their pitch decks claim. The right one depends on how many systems you’re touching, how fast you need to move, and whether your team can tolerate a rewrite gap. Match the partner to the shape of your problem, not the size of their logo.
Frequently Asked Questions
How much do top legacy modernization companies charge for a migration project?
Most firms in this space quote per project rather than publishing rate cards, since scope varies heavily by codebase size and migration complexity. Mid-range specialists tend to price lower than premium global integrators. Expect a discovery phase before any firm gives a firm estimate.
How do I choose the best top legacy modernization companies for my platform?
Start with stack fit – confirm the firm has shipped real migrations on your exact technology, whether that’s AngularJS, WinForms, or Delphi. Then check whether they assess before rewriting, since that signals engineering judgment over template execution. Team certifications and review depth matter too.
What services do top legacy modernization companies typically provide?
Core services usually include codebase assessment, architecture redesign, phased migration execution, and cloud re-platforming across AWS, Azure, or GCP. Many also handle framework upgrades, like moving Web Forms to ASP.NET Core, without pausing feature development on the live system.
