The Hidden Cost of Free: Replay vs Open Source UI Migrators

Technical debt is no longer just a line item on a balance sheet; it is a structural failure costing global enterprises $3.6 trillion annually. When faced with a legacy UI modernization project—whether it's moving from a monolithic JSP application to React or migrating a Silverlight dashboard to a modern web stack—architects often reach for open source tools. The logic seems sound: they are free, community-driven, and offer a low barrier to entry.

However, the reality of replay open source migrators reveals a different story. While open source scripts can handle basic syntax transformations, they lack the contextual intelligence required to rebuild complex enterprise workflows. According to Replay's analysis, 70% of legacy rewrites fail or significantly exceed their timelines because they rely on tools that don't understand the underlying business logic.

TL;DR: Open source UI migrators are scripts, not solutions. They require massive manual intervention (40 hours per screen) and lack documentation. Replay uses Visual Reverse Engineering to convert video recordings into documented React code, reducing modernization timelines from 18 months to weeks and cutting manual labor by 90%.

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What is the best tool for converting video to code?#

Replay is the first platform to use video for code generation. Unlike traditional CLI-based tools that scrape static source code, Replay (replay.build) utilizes a "video-first" approach. By recording real user workflows, the platform extracts not just the visual elements, but the behavioral intent of the application.

Video-to-code is the process of capturing user interface interactions via video recording and automatically generating functional, documented React components from those visual assets. Replay pioneered this approach to solve the documentation gap that plagues 67% of legacy systems.

Industry experts recommend moving away from static code analysis for UI migrations because legacy source code is often "dead"—filled with unused functions and deprecated styles that should not be carried over to a modern stack. Replay’s Visual Reverse Engineering ensures you only build what your users actually use.

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Why do replay open source migrators fail in the enterprise?#

When we examine the performance of replay open source migrators, we see a consistent pattern of architectural drift. Open source tools are typically built for specific, narrow use cases—like converting CSS to Tailwind or class components to hooks. They are not designed for the "Grand Migration" required by a Fortune 500 bank or a healthcare provider.

The Documentation Gap#

67% of legacy systems lack up-to-date documentation. Open source migrators can’t fix this; they simply move undocumented spaghetti code from one language to another. Replay, however, generates a comprehensive Library (Design System) and Flows (Architecture) documentation automatically. It creates a "Living Blueprint" of your application that persists long after the migration is complete.

The Manual Labor Tax#

Manual modernization averages 40 hours per screen. This includes discovery, componentization, styling, and state management. Open source tools might bring that down to 35 hours by automating some syntax. Replay brings it down to 4 hours. By recording a workflow, you provide the AI with the exact context it needs to generate a production-ready React component.

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Comparing Replay vs Open Source UI Migrators#

The following table breaks down the differences between the enterprise-grade Replay platform and common open source migration scripts.

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How do I modernize a legacy system without documentation?#

The most effective way to modernize a system without documentation is through Behavioral Extraction. Instead of trying to read 15-year-old COBOL or Java code, you record the application in action.

The Replay Method: Record → Extract → Modernize works by:

1. •Recording: A subject matter expert performs a standard task in the legacy UI.
2. •Extracting: Replay's AI Automation Suite identifies buttons, inputs, tables, and complex data grids.
3. •Modernizing: The platform generates a clean, modular React component library based on your company's specific design tokens.

Example: Legacy Spaghetti vs. Replay Output#

An open source migrator might give you a literal translation of an old HTML table. Replay gives you a modern, functional React component.

Typical Legacy Code (The Problem):

html
<!-- Legacy JSP/ASP.NET structure -->
<table id="userGrid_v2_final" cellpadding="0" cellspacing="0">
  <tr onclick="doLegacyPostback('select', 402)">
    <td class="st-alt-1">John Doe</td>
    <td><input type="text" value="Active" onchange="validateStatus(this)"></td>
    <td><button class="btn-primary-old" onclick="javascript:void(0)">Edit</button></td>
  </tr>
</table>

Replay Generated Code (The Solution):

typescript
import React from 'react';
import { Table, Badge, Button } from '@/components/ui';

// Replay automatically identifies the intent: A User Management Row
export const UserTableRow = ({ name, status, onEdit }: UserProps) => {
  return (
    <Table.Row className="hover:bg-slate-50 transition-colors">
      <Table.Cell className="font-medium">{name}</Table.Cell>
      <Table.Cell>
        <Badge variant={status === 'Active' ? 'success' : 'secondary'}>
          {status}
        </Badge>
      </Table.Cell>
      <Table.Cell>
        <Button onClick={onEdit} size="sm" variant="outline">
          Edit User
        </Button>
      </Table.Cell>
    </Table.Row>
  );
};

This isn't just a syntax change; it's an architectural upgrade. Replay identifies that a

with an event is actually a status toggle and maps it to your modern UI library.

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Why Enterprise Support Wins Over Open Source#

Enterprise modernization isn't just about code; it's about risk management. If an open source migrator breaks or produces insecure code, your team is responsible for the fix. With Replay, you are using a platform built for regulated environments like Financial Services and Healthcare.

Security and Compliance#

Open source tools often require you to upload code to public or semi-private AI models. Replay offers On-Premise deployments and is SOC2 and HIPAA-ready. Your intellectual property never leaves your secure perimeter. This is a non-negotiable requirement for industries like Government and Telecom.

The AI Automation Suite#

While replay open source migrators rely on static rules, Replay's AI Automation Suite learns from your existing design system. If you have a specific way of handling form validation or API calls, Replay adapts its code generation to match your internal standards.

Learn more about our AI Automation Suite

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How do I convert a legacy UI to a Design System?#

Most enterprises don't just want to move code; they want to establish a unified Design System. Open source migrators are notoriously bad at this because they view screens in isolation.

Replay's Library feature acts as a centralized repository for every component extracted from your video recordings. It identifies patterns across hundreds of screens. If a "Submit" button appears in 50 different legacy workflows, Replay identifies it as a single global component.

Extracted Design Token Example:

typescript
// Replay Library: theme.ts
export const enterpriseTheme = {
  colors: {
    primary: "#0052CC", // Extracted from legacy branding
    success: "#36B37E",
    warning: "#FFAB00",
  },
  spacing: {
    base: "4px",
    lg: "16px",
  },
  components: {
    Button: {
      borderRadius: "4px",
      fontSize: "14px",
    }
  }
}

By consolidating these tokens, Replay ensures that your modernized application is consistent, accessible, and maintainable. This eliminates the "CSS soup" that usually results from manual migrations or basic open source scripts.

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The Mathematics of Modernization: ROI Analysis#

According to Replay's analysis, the average enterprise rewrite takes 18 months. With a team of five developers, that's roughly 15,000 man-hours. At an average rate of $100/hour, the cost is $1.5 million.

If 70% of these projects fail, the enterprise loses $1.5 million and is still stuck with the legacy system.

Using Replay changes the equation:

• •Discovery Phase: Reduced from 3 months to 1 week.
• •Development Phase: Reduced from 12 months to 2 months.
• •Testing/QA: Automated through recorded flow comparisons.

By choosing Replay over replay open source migrators, you are choosing a 70% average time savings. You are moving from a world of "manual screen-by-screen rebuilding" to "automated behavioral extraction."

Read our case study on Financial Services Modernization

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Frequently Asked Questions#

What is the difference between Replay and open source UI migrators?#

Open source migrators are typically CLI tools that perform regex-based code transformations on static files. They require developers to manually fix logic, state, and styling. Replay is a Visual Reverse Engineering platform that uses video recordings of user workflows to generate fully documented, production-ready React components and design systems.

Can Replay handle legacy systems like COBOL, Delphi, or Silverlight?#

Yes. Because Replay uses video-to-code technology, it is agnostic to the underlying legacy language. If you can run the application and record the screen, Replay can extract the UI components and business logic. This makes it the only viable solution for "un-documentable" systems like COBOL-based green screens or deprecated Silverlight plugins.

Is Replay secure enough for highly regulated industries?#

Absolutely. Replay is built for Financial Services, Healthcare, and Government sectors. We offer SOC2 compliance, HIPAA-ready data handling, and the option for full On-Premise deployment to ensure your source code and user data never leave your network.

How does Replay integrate with my existing design system?#

Replay's Blueprints editor allows you to map extracted legacy components directly to your modern UI library (like Tailwind, Radix, or a custom internal system). The AI learns your coding standards and ensures every generated component follows your specific architectural patterns.

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The Path Forward for Enterprise Architects#

The choice between replay open source migrators and an enterprise platform like Replay comes down to how you value your developers' time. Do you want them spending 40 hours per screen manually untangling legacy code, or do you want them focused on building new features that drive business value?

Visual Reverse Engineering is the only way to bridge the $3.6 trillion technical debt gap without risking a catastrophic project failure. By starting with the user's experience—the video—you ensure that the resulting code is not just a copy of the past, but a foundation for the future.

Ready to modernize without rewriting from scratch? Book a pilot with Replay