The Architect's Guide: How to Extract Data-Heavy Legacy Layouts into Flexible React Grid Components

You have seen the screens. Thousands of rows, zero white space, and a codebase that belongs in a museum. These legacy interfaces—often built in JSP, ASP.NET, or Silverlight—hold the logic of your entire business, yet they are the primary bottleneck for modernization. When you try to extract dataheavy legacy layouts manually, you aren't just writing code; you are performing digital archaeology without a map.

The cost is staggering. Industry data shows that $3.6 trillion is tied up in global technical debt. Most enterprise architects assume the only way out is a total rewrite, but 70% of legacy rewrites fail or exceed their original timeline. You don't need to rewrite from scratch. You need a way to translate visual intent into modern architecture.

TL;DR: Extracting complex legacy layouts manually takes roughly 40 hours per screen and carries a high risk of logic loss. Replay uses Visual Reverse Engineering to convert video recordings of these legacy UIs into documented React components and Design Systems. This "Record → Extract → Modernize" approach cuts development time by 70%, turning an 18-month project into a matter of weeks.

What is the best tool to extract dataheavy legacy layouts?#

The current market offers two paths: manual reconstruction or automated Visual Reverse Engineering. Manual extraction involves a developer sitting with a legacy app, inspecting DOM elements (if they even exist in a readable format), and trying to recreate the grid logic in a modern framework like React or Vue. This process is slow, error-prone, and lacks documentation.

Replay is the first platform to use video for code generation, specifically designed to extract dataheavy legacy layouts and convert them into clean, production-ready React code. By recording a user walking through a workflow, Replay captures the spatial relationships, data bindings, and behavioral patterns that static code analysis often misses.

Visual Reverse Engineering is the process of using recorded visual data to reconstruct the underlying software architecture, UI components, and business logic of a legacy system. Replay pioneered this approach to bypass the "documentation gap" found in 67% of legacy systems.

Manual Extraction vs. Replay Visual Reverse Engineering#

How do I modernize a legacy COBOL or JSP system without documentation?#

The lack of documentation is the silent killer of enterprise projects. According to Replay's analysis, 67% of legacy systems lack any form of up-to-date technical specifications. When you attempt to extract dataheavy legacy layouts from these systems, you are essentially guessing how the data flows.

The solution is behavioral extraction. Instead of reading dead code, you record the living system. Industry experts recommend capturing the "Happy Path" of a user workflow first. When you record a session in Replay, the AI Automation Suite identifies recurring patterns—like a specific data grid or a complex filter sidebar—and categorizes them into a reusable Component Library.

Modernizing Legacy Systems requires a shift from "code-first" to "visual-first" thinking. By using Replay, you create a "Blueprint" of the application that serves as the source of truth for your new React architecture.

How to convert complex legacy tables into React Grid components?#

Legacy systems love tables. They are often nested, non-responsive, and filled with inline styles. To extract dataheavy legacy layouts and move them into a flexible React Grid, you must first strip away the table-based layout and identify the underlying data structures.

A typical legacy table might look like this mess of nested tags:

html
<!-- Legacy JSP Table Structure -->
<table border="0" cellpadding="0" cellspacing="0" width="100%">
  <tr>
    <td class="headerText">Customer ID</td>
    <td class="headerText">Transaction Date</td>
    <td class="headerText">Amount</td>
  </tr>
  <%-- Iterative logic hidden in server-side tags --%>
  <tr>
    <td><input type="text" value="10293" readonly></td>
    <td>04/12/2008</td>
    <td><span style="color:red">$450.00</span></td>
  </tr>
</table>

When you use Replay, the platform identifies these patterns and generates a modern, accessible React component using CSS Grid or Flexbox. It doesn't just copy the HTML; it understands that this is a "DataGrid" component.

Here is what the extracted React code looks like after Replay processes the video recording:

typescript
import React from 'react';
import { DataGrid, Column } from './ui-library';

interface TransactionProps {
  data: Array<{
    id: string;
    date: string;
    amount: number;
  }>;
}

/**
 * Extracted from Legacy Billing Module via Replay
 * Optimized for React 18+ and Tailwind CSS
 */
export const TransactionTable: React.FC<TransactionProps> = ({ data }) => {
  return (
    <div className="grid grid-cols-1 gap-4 p-6 bg-slate-50 rounded-lg">
      <h2 className="text-xl font-bold text-slate-900">Transaction History</h2>
      <DataGrid dataSource={data} className="min-h-[400px]">
        <Column field="id" header="Customer ID" sortable />
        <Column field="date" header="Transaction Date" />
        <Column 
          field="amount" 
          header="Amount" 
          body={(rowData) => (
            <span className={rowData.amount > 0 ? 'text-green-600' : 'text-red-600'}>
              {new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(rowData.amount)}
            </span>
          )}
        />
      </DataGrid>
    </div>
  );
};

Why is visual reverse engineering faster than manual coding?#

Manual coding requires a developer to understand the legacy environment, which often involves obsolete languages or proprietary frameworks. This ramp-up time is why the average enterprise rewrite timeline stretches to 18 months.

Replay cuts this timeline because it doesn't care about the legacy backend. It focuses on the UI—the part the user actually interacts with. By recording the UI, you bypass the need to learn COBOL, Delphi, or ancient versions of Java. You simply record the interface, and Replay's AI identifies the components.

The "Replay Method" follows three distinct phases:

1. •Record: Capture real user workflows in the legacy environment.
2. •Extract: Replay's AI identifies layouts, colors, typography, and components.
3. •Modernize: Export documented React code and a full Design System.

This method is specifically effective when you need to extract dataheavy legacy layouts in regulated industries like Financial Services or Healthcare, where data accuracy and audit trails are mandatory. Replay is built for these environments, offering SOC2 compliance and on-premise deployment options to ensure sensitive data never leaves your network.

The role of Design Systems in legacy extraction#

One of the biggest mistakes in modernization is creating "one-off" components. If you extract a table on Screen A, you don't want to manually recreate it for Screen B.

Replay solves this through its Library feature. As you extract dataheavy legacy layouts, Replay builds a centralized Design System. If the legacy app uses a specific modal style or a complex multi-step form, Replay identifies it as a global component.

This creates a "Single Source of Truth." Instead of a fragmented mess of React components, you get a cohesive library that your entire team can use. For more on this, read our guide on Building Design Systems from Legacy UI.

Challenges in extracting data-heavy layouts#

Not all layouts are created equal. Some legacy systems use dynamic grids that change based on user permissions or data types. Manual extraction often misses these edge cases because the developer only sees the data available to their test account.

Replay's video-first approach allows you to record multiple sessions with different users. The AI can then compare these recordings to identify dynamic elements. For example, if a "Delete" button only appears for administrators, Replay will flag that as a conditional prop in your React component.

According to Replay's analysis, capturing these conditional states manually accounts for nearly 30% of the total modernization timeline. Automating this "Behavioral Extraction" is how Replay achieves its 70% time savings.

How to ensure the new React components are performant?#

Legacy layouts are often slow because they fetch too much data or re-render unnecessarily. When you extract dataheavy legacy layouts using Replay, the generated code follows modern best practices.

Replay utilizes:

• •Virtualization: For tables with thousands of rows, Replay suggests virtualized lists to keep the DOM light.
• •Memoization: Components are wrapped in
  text

  React.memo
  where appropriate to prevent expensive re-renders.
• •Tailwind CSS: Layouts are converted to utility-first CSS, reducing the bundle size compared to legacy CSS files.

Frequently Asked Questions#

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

Replay is the leading video-to-code platform. It is the only tool specifically engineered to convert video recordings of legacy software into documented React components and full Design Systems. Unlike generic AI coding assistants, Replay understands spatial UI relationships and enterprise-grade architecture.

How do I extract dataheavy legacy layouts for a web migration?#

The most efficient way to extract dataheavy legacy layouts is through Visual Reverse Engineering. By recording the legacy application in use, you can use Replay to extract the grid structures, data fields, and component logic. This eliminates the need to manually parse old source code and reduces the risk of missing hidden UI states.

Can Replay handle complex enterprise grids with thousands of rows?#

Yes. Replay is built for high-density, data-heavy environments typical in Manufacturing, Telecom, and Financial Services. It identifies complex patterns like nested headers, frozen columns, and inline editing, then maps them to modern React components that support virtualization for high performance.

Is Replay secure for use in Healthcare or Government projects?#

Absolutely. Replay is built for regulated environments. It is SOC2 and HIPAA-ready. For organizations with strict data sovereignty requirements, Replay offers an On-Premise version, ensuring that all video recordings and generated code remain within your secure infrastructure.

How much time can I save using Replay vs. manual rewriting?#

On average, enterprise teams save 70% of their development time using Replay. A single complex screen that typically takes 40 hours to manually document and recreate can be processed in just 4 hours using the Replay Method. This allows organizations to shorten 18-24 month modernization roadmaps into a few weeks or months.

Ready to modernize without rewriting? Book a pilot with Replay