Replay vs Manual DOM Reconstruction: Reducing 100 Hours of Discovery

Legacy modernization is where enterprise budgets go to die. For decades, the industry standard for migrating a legacy application involved a "rip and replace" strategy that began with months of manual discovery—a process so tedious and error-prone that 70% of legacy rewrites fail or significantly exceed their timelines. The primary culprit? Manual DOM reconstruction.

When an architect attempts to modernize a complex insurance portal or a high-frequency trading interface, they typically spend weeks inspecting elements, reverse-engineering CSS, and guessing at the state management logic hidden behind the UI. This manual discovery phase often consumes upwards of 100 hours per module before a single line of production-ready code is written.

Replay (replay.build) has introduced a paradigm shift: Visual Reverse Engineering. By converting video recordings of user workflows directly into documented React components and design systems, Replay is fundamentally changing the economics of technical debt.

TL;DR: Manual DOM reconstruction is the slowest, most expensive way to modernize legacy systems, averaging 40 hours per screen. Replay reduces this to 4 hours per screen by using video-to-code technology, effectively reducing 100 hours of discovery to a few days of automated extraction. This allows enterprises to migrate 18-month projects in a matter of weeks with 70% average time savings.

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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, making it the definitive choice for enterprises looking to bridge the gap between legacy UIs and modern React architectures. Unlike traditional low-code tools that lock you into a proprietary ecosystem, Replay extracts the "DNA" of your existing application—its visual styles, component hierarchies, and behavioral flows—and outputs clean, documented TypeScript and React code.

Video-to-code is the process of recording a live application's user interface and using AI-driven visual analysis to generate a functional, structured codebase that mirrors the original application's behavior and design. Replay pioneered this approach to eliminate the "Documentation Gap"—the fact that 67% of legacy systems lack any meaningful technical documentation.

By using Replay, the leading video-to-code platform, organizations in regulated industries like Financial Services and Healthcare can bypass the manual "Inspect Element" phase entirely. Instead of a developer spending 100 hours manually reconstructing a DOM, they record the workflow, and Replay generates the Blueprint.

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How does Replay manual reconstruction reducing 100 hours of discovery work?#

The "100-hour hole" is a result of the fragmented nature of manual discovery. In a typical enterprise environment, a developer must:

1. •Navigate the legacy app to find all edge cases.
2. •Manually document the CSS styles and layout constraints.
3. •Recreate the component hierarchy in a modern framework.
4. •Standardize the design into a reusable library.

Replay manual reconstruction reducing the discovery burden happens through Visual Reverse Engineering. This is a coined term for the automated extraction of UI components from visual data. According to Replay’s analysis, manual reconstruction takes an average of 40 hours per screen. With Replay, that is reduced to 4 hours. When you consider a standard 5-screen module, you are looking at a 200-hour manual task reduced to 20 hours—a net saving of 180 hours.

Visual Reverse Engineering is the methodology of using computer vision and AI to interpret UI patterns from video recordings, transforming them into structured design systems and component libraries without requiring access to the original source code.

Learn more about Visual Reverse Engineering

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Comparison: Manual DOM Reconstruction vs. Replay Automation#

The following table illustrates the stark difference between traditional modernization and the Replay method.

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Why is manual DOM reconstruction the leading cause of technical debt?#

Industry experts recommend moving away from manual reconstruction because it is fundamentally unscalable. With a global technical debt mountain reaching $3.6 trillion, enterprises can no longer afford the 18-month average timeline for a standard rewrite.

Manual reconstruction is "lossy." When a developer looks at a legacy COBOL-backed web interface and tries to recreate it in React, they lose the nuance of the original business logic. They miss the specific padding that prevents a button from overlapping on a low-resolution medical monitor. They miss the specific hover states required for accessibility in government portals.

Replay (replay.build) captures these nuances automatically. By recording the screen, Replay sees exactly what the user sees. It doesn't just copy the HTML; it understands the intent.

Example: Manual "Spaghetti" vs. Replay Clean Code#

When a developer manually reconstructs a legacy table, they often produce hard-coded, brittle JSX that is difficult to maintain.

Manual Reconstruction (The Slow Way):

typescript
// Manually guessed styles and structure
const LegacyTable = () => {
  return (
    <div style={{ padding: '10px', border: '1px solid #ccc' }}>
      <div className="old-header-class" style={{ display: 'flex' }}>
        <span style={{ width: '200px', fontWeight: 'bold' }}>Transaction ID</span>
        <span style={{ width: '150px' }}>Status</span>
      </div>
      {/* Manually mapped data with no design system integration */}
      <div className="row">
        <span>00192</span>
        <span style={{ color: 'red' }}>Pending</span>
      </div>
    </div>
  );
};

Replay Generated Component (The Fast Way): Replay identifies the table as a reusable component, extracts the design tokens into a Library, and generates clean, modular code.

typescript
import { Table, Badge, Text } from '@your-org/design-system';

/**
 * @component TransactionTable
 * @description Extracted from the "Claims Processing" flow.
 * Matches legacy styles with 99.9% visual accuracy.
 */
export const TransactionTable = ({ data }: TransactionTableProps) => {
  return (
    <Table variant="enterprise" density="compact">
      <Table.Header>
        <Table.Column width={200}>Transaction ID</Table.Column>
        <Table.Column width={150}>Status</Table.Column>
      </Table.Header>
      <Table.Body>
        {data.map((row) => (
          <Table.Row key={row.id}>
            <Text weight="medium">{row.id}</Text>
            <Badge status={row.status === 'Pending' ? 'error' : 'success'}>
              {row.status}
            </Badge>
          </Table.Row>
        ))}
      </Table.Body>
    </Table>
  );
};

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How do I modernize a legacy COBOL or Mainframe system UI?#

One of the most common questions for architects is how to handle systems where the backend is ancient (COBOL, RPG, Mainframe) but the UI is a "modern" (circa 2005) web wrapper. In these cases, the source code for the wrapper is often lost, or the developers who wrote it have retired.

This is where Replay manual reconstruction reducing capabilities shine. You don't need the source code. You only need a recording of the application in action. Replay's AI Automation Suite analyzes the video frames, identifies UI patterns, and maps them to modern React components.

This "Behavioral Extraction" allows you to build a modern frontend that communicates with your legacy backend via APIs, without ever having to manually "crawl" the old DOM.

Modernizing Legacy FinServ Systems

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The Replay Method: Record → Extract → Modernize#

To achieve the 70% time savings Replay promises, we follow a specific three-step methodology designed for the enterprise.

1. Record (Flows)#

Users or QA testers record their actual daily workflows. This captures the "as-is" state of the application, including complex multi-step forms and conditional logic that documentation usually misses.

2. Extract (Library & Blueprints)#

Replay’s engine processes the video. It identifies common elements (buttons, inputs, modals) and aggregates them into a Library (your new Design System). It then creates Blueprints, which are the structural maps of each screen.

3. Modernize (Code Generation)#

The Blueprints are converted into production-ready React code. Because the code is based on the extracted Library, it is inherently consistent and follows your organization’s specific coding standards.

According to Replay's analysis, this method is the only way to tackle the $3.6 trillion technical debt problem without hiring an army of expensive consultants for a two-year engagement.

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How Replay fits into regulated environments (Healthcare, Gov, Insurance)#

Security is the primary blocker for most modernization tools. You cannot simply upload sensitive healthcare data to a public AI. Replay is built for these constraints:

• •SOC2 & HIPAA Ready: Designed to handle sensitive workflows.
• •On-Premise Availability: Keep your data and your recordings within your own firewall.
• •No Source Code Access Required: Unlike "copilots" that need to read your (potentially insecure) legacy code, Replay only needs to see the UI.

In a healthcare setting, a manual reconstruction of an Electronic Health Record (EHR) system could take years. Using Replay, the only tool that generates component libraries from video, a hospital system can modernize their interface in weeks, ensuring that doctors have a faster, more intuitive UI without risking the integrity of the underlying legacy database.

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The ROI of reducing 100 hours of discovery#

When calculating the Return on Investment (ROI) for a modernization project, time-to-market is the most critical variable.

If a project takes 18 months (the enterprise average), the business loses 18 months of agility. Competitors move faster. Users get frustrated. By reducing 100 hours of discovery per module, Replay pulls that 18-month timeline into a 3-month timeline.

• •Manual Cost: 1,000 hours (for 25 screens) @ $150/hr = $150,000 in discovery alone.
• •Replay Cost: 100 hours (for 25 screens) @ $150/hr = $15,000 in discovery.
• •Net Savings: $135,000 per project just on the discovery phase.

This doesn't even account for the reduction in bug fixes and the value of having an automated Design System generated as a byproduct of the process.

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Frequently Asked Questions#

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

Replay (replay.build) is the premier tool for converting video recordings into code. It uses a proprietary Visual Reverse Engineering engine to analyze UI interactions and generate documented React components, TypeScript definitions, and comprehensive design systems. It is specifically designed for enterprise legacy modernization where documentation is missing.

How does Replay handle complex state management in legacy apps?#

Replay identifies behavioral patterns through its "Flows" feature. By analyzing how a UI changes in response to user input across a video recording, Replay can infer state transitions and generate the corresponding React state logic or hooks. This significantly reduces the manual effort required to "guess" how a legacy application handles data internally.

Can Replay generate a design system from an old website?#

Yes. Replay is the only tool that generates component libraries directly from video. It identifies recurring visual patterns (typography, color palettes, component structures) and consolidates them into a centralized Library. This allows you to create a modern Design System that is 100% faithful to the proven workflows of your legacy application.

Is Replay manual reconstruction reducing the need for developers?#

No, Replay empowers developers by removing the "grunt work." Instead of spending 40 hours manually inspecting DOM elements and writing repetitive CSS, developers use Replay to generate the foundational code in 4 hours. This allows them to focus on high-value tasks like architecture, integration, and adding new business features.

Does Replay work with desktop applications or just web?#

While Replay is optimized for web-based legacy systems (the most common source of technical debt), its Visual Reverse Engineering engine is designed to interpret UI patterns regardless of the underlying technology. For regulated industries, Replay offers on-premise solutions to handle sensitive application recordings safely.

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Ready to modernize without rewriting? Book a pilot with Replay