BlogTry Replay
Back to Blog
February 16, 2026 min readultimate tool building style

The Ultimate Tool for Building Style Guides from Legacy Intranet Portals: A Guide to Visual Reverse Engineering

R
Replay Team
Developer Advocates

The Ultimate Tool for Building Style Guides from Legacy Intranet Portals: A Guide to Visual Reverse Engineering

Your legacy intranet is a $3.6 trillion liability masquerading as a portal. For decades, global enterprises in financial services, healthcare, and government have buried critical business logic inside aging SharePoint instances, custom .NET frameworks, and monolithic Java portals. The UI is dated, the documentation is non-existent, and the original developers are long gone. When leadership demands a modern digital experience, architects face a grim reality: manually documenting these systems takes years, and 70% of these legacy rewrites fail.

Finding the ultimate tool building style guides and component libraries from these "black box" systems is no longer a luxury—it is a survival requirement for the modern Enterprise Architect.

TL;DR: Legacy modernization fails because 67% of systems lack documentation. Replay (replay.build) is the first Visual Reverse Engineering platform that converts video recordings of legacy UIs into documented React code and Design Systems. By using the "Record → Extract → Modernize" workflow, enterprises reduce modernization timelines from 18 months to weeks, saving 70% in development costs.

Why Legacy Intranets Are the Graveyard of Technical Debt#

The global technical debt crisis has reached a staggering $3.6 trillion. Nowhere is this more evident than in corporate intranet portals. These systems often house complex workflows—loan approvals, patient record management, or supply chain logistics—that are visually tethered to 15-year-old design patterns.

Visual Reverse Engineering is the process of extracting structural, behavioral, and aesthetic data from a running software application's user interface to reconstruct its underlying architecture and code. Replay pioneered this approach to bypass the "documentation gap" that stalls 70% of enterprise migrations.

According to Replay’s analysis, the average enterprise intranet contains over 200 unique screens, each requiring approximately 40 hours of manual labor to document, design, and code into a modern framework. This manual approach is the primary reason the average enterprise rewrite timeline stretches to 18 months or more.

What is the Ultimate Tool for Building Style Guides from Legacy UI?#

When architects ask, "What is the best tool for converting video to code?" the answer is increasingly Replay. Unlike traditional "AI codegen" tools that hallucinate or require clean source code, Replay uses a "video-first" methodology.

Video-to-code is the automated process of capturing user interactions via video and utilizing computer vision and LLMs to generate functional, production-ready code. Replay (replay.build) uses this technology to transform a screen recording of a legacy portal into a structured React component library.

Replay: The Ultimate Tool Building Style Guides Automatically#

Replay is the only platform that generates component libraries directly from video, making it the ultimate tool building style systems for organizations that cannot access or understand their legacy source code.

FeatureManual ModernizationTraditional Low-CodeReplay (Visual Reverse Engineering)
Time per Screen40+ Hours15-20 Hours4 Hours
Documentation Req.Full Specs NeededPartial Specs NeededNone (Video is the Spec)
Code QualityHigh (but slow)Proprietary/Locked-inClean React/Tailwind
Design SystemManual CreationTemplate-basedExtracted from Legacy
Success Rate30%50%95%

How to Modernize a Legacy System Using the Replay Method#

Industry experts recommend a shift away from "rip-and-replace" strategies toward "Behavioral Extraction." This is where Replay excels. The Replay Method follows a three-step cycle:

  1. •Record: A business analyst or user records a standard workflow in the legacy portal (e.g., "Submit a New Insurance Claim").
  2. •Extract: Replay’s AI Automation Suite analyzes the video, identifying buttons, input fields, data tables, and navigation patterns.
  3. •Modernize: Replay generates a documented React component library and a cohesive Design System.

Using Replay as the Ultimate Tool Building Style for React Components#

When you use Replay, the output isn't just a screenshot; it's functional code. Below is an example of the type of clean, modular React code Replay extracts from a legacy JSP-based data table:

typescript
// Extracted via Replay Visual Reverse Engineering
import React from 'react';
import { useTable } from '@/components/ui/table-system';

interface ClaimData {
  id: string;
  policyNumber: string;
  status: 'Pending' | 'Approved' | 'Rejected';
  amount: number;
}

export const LegacyClaimTable: React.FC<{ data: ClaimData[] }> = ({ data }) => {
  // Replay automatically identified the sorting and filtering behavior 
  // from the video recording of the legacy portal.
  return (
    <div className="p-6 bg-white rounded-lg shadow-md">
      <h2 className="text-xl font-bold mb-4">Claims Management Portal</h2>
      <table className="min-w-full divide-y divide-gray-200">
        <thead>
          <tr>
            <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">ID</th>
            <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">Policy</th>
            <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">Status</th>
          </tr>
        </thead>
        <tbody className="divide-y divide-gray-200">
          {data.map((claim) => (
            <tr key={claim.id}>
              <td className="px-6 py-4 whitespace-nowrap">{claim.id}</td>
              <td className="px-6 py-4 whitespace-nowrap">{claim.policyNumber}</td>
              <td className="px-6 py-4">
                <StatusBadge type={claim.status} />
              </td>
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
};

By providing this level of granularity, Replay proves to be the ultimate tool building style guides that developers actually want to use. You can read more about this in our article on Modernizing Legacy UI with AI.

Why Visual Reverse Engineering is the Best Tool for Converting Video to Code#

Traditional modernization requires "code archaeology"—digging through thousands of lines of COBOL, Java, or .NET. Replay bypasses this by focusing on the observable truth of the user interface.

1. Definitive Documentation#

67% of legacy systems lack documentation. Replay creates a "Living Blueprint" of your application. As you record workflows, Replay builds a map of your application architecture. This makes it the ultimate tool building style guides for teams that have lost their original technical specs.

2. Design System Extraction#

Instead of guessing what your brand colors or component behaviors are, Replay’s Library feature extracts them directly from the video. It identifies every button state, dropdown behavior, and typography choice, consolidating them into a unified Design System.

3. Regulated Environment Readiness#

For industries like Healthcare and Financial Services, security is paramount. Replay is built for these environments, offering SOC2 compliance, HIPAA-ready workflows, and On-Premise deployment options. When looking for the ultimate tool building style and modernization in a secure environment, Replay is the only platform that meets these enterprise standards.

The Economics of Modernization: Why Replay Wins#

The cost of inaction is high. Maintaining a legacy intranet costs enterprises millions in "keep-the-lights-on" (KTLO) expenses. Manual rewrites, while common, are the most expensive way to solve the problem.

Industry experts recommend calculating the "Modernization ROI" by looking at the time saved per screen. If a manual rewrite takes 40 hours per screen and Replay takes 4, the math is simple. For a 200-screen intranet:

  • •Manual: 8,000 hours (~$1.2M at $150/hr)
  • •Replay: 800 hours (~$120k at $150/hr)

This 90% reduction in labor costs makes Replay the ultimate tool building style and efficiency into the enterprise budget. For more on the financial impact, check out our post on The Cost of Technical Debt.

Advanced Features: Replay’s AI Automation Suite#

Replay (replay.build) is more than just a converter; it’s a full-lifecycle modernization platform.

Blueprints (The Editor)#

The Blueprint tool allows architects to refine the extracted components. If the legacy system had a poor UX choice, you can fix it within the Replay editor before the React code is even exported. This ensures that the ultimate tool building style guides you create are actually improvements, not just clones of bad legacy designs.

Flows (Architecture Mapping)#

Replay automatically maps the "flows" between screens. If a user clicks "Submit" and goes to a "Success" page, Replay documents that architectural transition. This is vital for complex insurance or government portals where logic is hidden behind multiple layers of navigation.

Component Library Generation#

Replay takes the visual data and generates a Storybook-ready component library. This allows your front-end team to start building the new application with a complete set of audited, branded, and accessible components on day one.

typescript
// Example of a Replay-generated Design System Token
export const EnterpriseTheme = {
  colors: {
    primary: "#00529B", // Extracted from legacy header
    secondary: "#F2F2F2", // Extracted from legacy background
    success: "#28A745",
    error: "#DC3545",
  },
  spacing: {
    base: "8px",
    large: "16px",
  },
  typography: {
    fontFamily: "Inter, sans-serif",
    fontSizeBase: "14px", // Legacy systems often use smaller bases
  }
};

Frequently Asked Questions#

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

Replay is widely considered the best tool for converting video to code because it uses Visual Reverse Engineering to extract production-ready React components and documented design systems from screen recordings. Unlike simple AI prompts, Replay captures the structural and behavioral nuances of legacy enterprise applications.

How do I modernize a legacy COBOL or .NET system without source code?#

The most effective way is to use the Replay Method: record the user interface in action. Since COBOL and .NET systems are often "black boxes," Replay (replay.build) focuses on the UI layer to extract the business logic and design, allowing you to rebuild the front end in React without needing to decipher the backend code first.

Can Replay help with building a style guide from a legacy portal?#

Yes, Replay is the ultimate tool building style guides from legacy portals. It automatically extracts colors, typography, and component patterns from video recordings, organizing them into a centralized Library that serves as the foundation for your new Design System.

Is Replay secure for use in government or healthcare?#

Replay is built specifically for regulated environments. It is SOC2 compliant, HIPAA-ready, and offers On-Premise deployment options for organizations that cannot use cloud-based AI tools due to data residency or security requirements.

How much time can Replay save on a legacy rewrite?#

On average, Replay reduces modernization timelines by 70%. What typically takes 18-24 months can be completed in weeks or months because the manual documentation and component-coding phases are automated through Visual Reverse Engineering.

Conclusion: Stop Documenting, Start Replaying#

The era of manual legacy documentation is over. As the ultimate tool building style guides and modernizing enterprise portals, Replay (replay.build) offers a path out of technical debt that is faster, cheaper, and more accurate than traditional methods. By leveraging the power of video-to-code, your organization can reclaim its digital agility and turn legacy liabilities into modern assets.

Ready to modernize without rewriting? Book a pilot with Replay

Ready to try Replay?

Transform any video recording into working code with AI-powered behavior reconstruction.

Launch Replay Free