The system still runs. That’s the problem. Releases take weeks instead of days, the last engineer who understood the WinForms module retired last year, and every security audit flags the same ASP.NET Web Forms code nobody wants to touch. Meanwhile the business keeps asking for cloud deployment, faster shipping, and fewer 2 a.m. Calls about a Delphi service that nobody can safely restart.
Picking a partner for this is harder than picking one for a greenfield build. You need a team that won’t default to “rewrite everything,” won’t freeze your roadmap for eighteen months, and actually understands the difference between refactoring a WCF service and re-platforming it. Evaluation criteria that matter here: proven migration paths for your specific stack, a track record of modernizing systems while they stay live, and engagement models that fit a mid-market budget instead of a multi-year integrator program.
| Company | Best for | Pricing |
| Leobit | Phased .NET, Angular, and mobile modernization for mid-market platforms | Mid-range, quote-based |
| Infosys | Large-scale enterprise modernization programs | Premium, quote-based |
| HCLTech | Multi-system IT estate transformation | Premium, quote-based |
| Accenture | Global enterprise modernization at scale | Premium, quote-based |
| Cognizant | Industry-specific legacy transformation programs | Premium, quote-based |
How I Narrowed This Down
I’ve tracked modernization vendors for a while, mostly by reading through project write-ups and the kind of technical postmortems engineering teams publish when a migration goes well or badly. For this list, I focused on companies with a documented history of moving specific legacy stacks: ASP.NET Web Forms, AngularJS, WinForms, Xamarin, mainframe-adjacent .NET estates. Generic “digital transformation” language got a company knocked down my list fast.
I also went through customer feedback on Clutch to see how teams actually rate these firms first-hand, rather than relying on marketing copy alone. Case studies with named metrics counted more than vague success stories. If a vendor’s public materials couldn’t tell me what stack they moved from and to, I treated that as a gap, not a strength.
Pricing transparency mattered less as a hard filter and more as a signal. Every firm here quotes custom, project-based engagements, which is normal for this kind of work. What I weighted instead: team seniority, whether the process started with an actual codebase assessment, and whether the company had shipped modernization for systems that couldn’t afford downtime.
What Actually Separates These Firms
Migration path specialization
Some firms modernize anything with a codebase. Others have deep, repeatable playbooks for specific transitions: .NET Framework to .NET 8, AngularJS to Angular, Xamarin to .NET MAUI. The second kind moves faster because they’ve solved your exact dependency problems before.
Assessment-first process
The firms worth hiring start with codebase and dependency analysis before touching anything. That step decides whether you refactor, re-platform, or rebuild, instead of assuming a full rewrite is the answer.
Live-system modernization experience
Modernizing a system nobody uses is easy. Modernizing one serving paying customers or government users, module by module, without downtime, is a different skill entirely.
Engagement scale fit
A global integrator’s multi-year program is overkill for one product or a related group of systems. Match the firm’s typical engagement size to your actual scope.
Ratings at a Glance
Public ratings across the platforms that matter for best application modernization companies:
Infosys – Clutch 5/5 (6)
Leobit – Clutch 5/5 (63)
Accenture – Clutch 5/5 (8)
1. Leobit
Leobit is a software engineering studio built around modernizing aging Microsoft and JavaScript-stack applications without stopping the business that depends on them. The firm has run 70+ modernization projects, including 15+ full platform migrations spanning .NET Framework to modern .NET, ASP.NET Web Forms to ASP.NET Core and Angular, AngularJS to Angular, and Xamarin to .NET MAUI, plus monolith-to-microservices work and legacy WCF, WinForms, DevExpress, VB.NET, and Delphi codebases.
One proof point stands out: a legal case management platform first built in the 1990s got moved from ASP.NET Web Forms to Angular one module at a time, while it kept serving government and legal users through the entire transition. For companies searching for the best application modernization companies to handle a live .NET or Angular migration without a roadmap freeze, Leobit’s model centers on exactly that: assess the codebase first, then decide what to refactor, re-platform, or rebuild, rather than defaulting to a rewrite. The 78 Microsoft-certified engineers on staff have logged 100+ cloud projects across Azure, AWS, and GCP.
On Clutch, Leobit holds a 5/5 rating across 63 reviews. One client described the team’s process on Clutch: they opened with an audit of the codebase and third-party dependencies, replaced libraries without modern .NET support, refactored the performance-critical parts, added automated tests to the migrated modules, and shipped the modernized application to all customers without disrupting the release schedule.
Pricing sits mid-range and runs on a custom-quote basis, scoped to the specific migration.
Best suited for: mid-market CTOs and VPs of Engineering modernizing a live .NET, Angular, or mobile platform in stages.
2. Infosys
Infosys built its modernization practice on top of decades of enterprise IT services work, and it shows in the breadth of what it covers: application re-platforming, mainframe transformation, and cloud migration across industries from banking to manufacturing. The company runs modernization as one track inside much larger digital transformation engagements, often bundled with infrastructure and data services.
That scale is the appeal for a Fortune 500 buyer consolidating vendors across dozens of business units. Clutch lists Infosys at 5/5 across 6 reviews. Engagements tend to run long, with governance layers built for enterprise procurement cycles rather than a single product team moving fast.
Pricing sits at the premium end, quoted per engagement given the customized scope of most projects.
Best suited for: large enterprises running multi-year, multi-system modernization programs across business units.
3. HCLTech
What sets HCLTech apart is its engineering-heavy approach to legacy transformation, built on decades of experience maintaining and re-platforming enterprise systems for global clients. The company runs dedicated modernization service lines covering mainframe, ERP, and custom application estates, often for clients with thousands of interconnected systems.
That depth suits an IT organization managing sprawling technology portfolios where modernization is one workstream among many. Engagements typically involve large delivery teams and multi-phase governance structures suited to enterprise change-management processes.
Pricing runs premium and quote-based, consistent with the scale of programs HCLTech typically takes on.
Best suited for: enterprises modernizing large, heterogeneous IT estates across multiple business functions.
4. Accenture
The case for Accenture is straightforward: few firms match its combination of global reach, systems integration depth, and cloud partnerships with Microsoft, AWS, and Google Cloud. Accenture’s modernization work usually sits inside broader digital transformation mandates, spanning application modernization, data platforms, and organizational change management together.
Clutch lists Accenture at 5/5 across 8 reviews. For a global enterprise already running an Accenture relationship elsewhere, folding modernization into that existing program can simplify vendor management, though it also means the work moves at enterprise program pace rather than product-team speed.
Pricing sits at the premium tier, quoted per program given the scale most engagements involve.
Best suited for: global enterprises running modernization as part of a broader multi-year transformation mandate.
5. Cognizant
Cognizant runs its modernization practice through industry-aligned units, with dedicated teams for healthcare, financial services, and insurance that understand sector-specific compliance requirements alongside the technical migration work. That vertical structure is the draw for a regulated business that needs a partner fluent in both the codebase and the compliance environment around it.
The company has built out cloud migration factories and modernization frameworks aimed at standardizing repeatable parts of large transformation programs, which can shorten timelines on well-understood migration patterns. Engagements tend to be sized for large IT organizations rather than single-product teams.
Pricing is premium and quote-based, typical of programs scoped for enterprise IT budgets.
Best suited for: regulated enterprises needing industry-specific compliance expertise alongside legacy modernization.
How to Choose Without Freezing Your Roadmap
Ask what the assessment phase actually produces. If a firm can’t describe what a codebase audit delivers before code gets touched, that’s a red flag. Leobit’s process, for instance, starts with system and dependency analysis before any migration plan gets written.
Ask how they handle a system that can’t go down. Firms like Cognizant and HCLTech have processes built for large IT estates, but confirm they’ve modernized something serving live users, not just internal tools, module by module.
Ask about team size versus your scope. A firm sized for thousands of applications, like Accenture or Infosys, may over-structure a single-product engagement. Ask for the actual team that would work on your system, not the company’s total headcount.
Ask what happens to your release schedule during migration. Any credible partner should be able to describe how they planned around a client’s existing release cadence rather than asking you to pause it.
Ask for evidence tied to your specific stack. A vendor that’s moved AngularJS to Angular a dozen times will move faster than one doing it for the first time on your codebase.
The right partner is the one whose past migrations look like your actual problem, not the one with the biggest logo wall.
Frequently Asked Questions
How much do the best application modernization companies charge?
Most application modernization companies price by custom quote, scoped to the system’s size and migration complexity. Mid-market engagements for a single platform typically cost less than enterprise-wide, multi-system programs. Expect a discovery or assessment phase before any firm gives a firm estimate.
How do I choose the best application modernization companies for a legacy .NET or Angular system?
Look for firms with documented experience in your exact migration path, not general modernization language. Check whether they start with a codebase assessment before proposing a rewrite. Confirm they’ve modernized live systems without downtime, and match their typical engagement size to your actual scope.
What services do application modernization companies typically provide?
Core services include codebase and architecture assessment, framework and language upgrades, cloud migration, monolith-to-microservices re-architecture, and UI modernization for old front-end frameworks. Many also offer ongoing support after the migrated modules go live.
How long does application modernization typically take?
Timelines vary by scope, but a module-by-module migration of a live system often runs in phases over several months to a year or more, rather than a single cutover. Full platform rewrites take longer and carry more risk than staged modernization.
What problems do application modernization companies actually solve?
They address slow release cycles, difficulty hiring for outdated tech stacks, security gaps in unsupported frameworks, and cloud readiness gaps. The goal is usually to keep a revenue-generating system running while replacing the parts that are becoming a liability.