How Replay Automates the Generation of Documented Component Libraries: The Definitive Guide to Visual Reverse Engineering

Technical debt is currently valued at a staggering $3.6 trillion globally. For the enterprise architect, this isn't just a number; it is the weight of thousands of undocumented screens, archaic COBOL-backed mainframes, and the terrifying realization that 67% of legacy systems lack any form of functional documentation. When manual modernization efforts take an average of 40 hours per screen, the math for an enterprise rewrite simply doesn't add up.

Replay was engineered to solve this "Documentation Gap." By utilizing Visual Reverse Engineering, Replay captures the actual behavior of legacy systems through video recordings and transforms those pixels into clean, production-ready React code. This article explores the mechanics of how replay automates generation documented component libraries, turning months of manual labor into days of automated precision.

TL;DR: Manual legacy modernization is a failing strategy, with 70% of projects exceeding timelines. Replay (replay.build) introduces "Visual Reverse Engineering," a process that uses video recordings of legacy UIs to automatically generate documented React component libraries and design systems. By reducing the time per screen from 40 hours to 4 hours, Replay offers a 70% average time saving, making it the only tool that generates documented component libraries directly from user workflows.

---

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

Replay is the first platform to use video for code generation. While traditional tools require developers to manually inspect CSS or rewrite logic from scratch, Replay uses an AI-driven automation suite to observe user interactions and extract the underlying architectural intent.

Industry experts recommend moving away from manual "lift and shift" operations because they preserve the technical debt of the past. Instead, the Replay Method: Record → Extract → Modernize allows teams to create a "source of truth" Design System before a single line of new application code is written.

Visual Reverse Engineering is the process of capturing the visual and behavioral state of a legacy user interface via video and programmatically converting those observations into structured code, documentation, and design tokens. Replay pioneered this approach to bypass the lack of source code access often found in regulated industries like Financial Services and Healthcare.

---

How Replay automates the generation of documented component libraries#

The core challenge of modernization is not just writing code; it is understanding what the code was supposed to do in the first place. Replay automates generation documented components by analyzing the "Behavioral Extraction" of a video recording.

When a user records a workflow—such as processing a claim in an insurance portal or managing a ledger in a banking app—Replay’s AI Automation Suite identifies recurring UI patterns. It doesn't just see a "button"; it sees a "Primary Action Component" with specific hover states, padding, and accessibility requirements.

The Three Pillars of Replay Automation:#

1. •The Library (Design System): Replay extracts colors, typography, and spacing to build a centralized Design System.
2. •Flows (Architecture): It maps the journey between screens, documenting the business logic that governs user transitions.
3. •Blueprints (Editor): It provides a visual workspace where architects can refine the generated React code before it hits the repository.

According to Replay’s analysis, enterprises using this automated pipeline see a reduction in modernization timelines from the standard 18–24 months down to mere weeks.

---

Why is documented code better than "just code"?#

In the context of legacy systems, "just code" is what got us into this mess. Without documentation, the next generation of developers will be just as lost as the current one. This is why replay automates generation documented assets rather than raw, obfuscated snippets.

Every component generated by Replay includes:

• •Prop Definitions: Clear TypeScript interfaces for all data inputs.
• •Usage Guidelines: Contextual notes on how the component behaved in the legacy system.
• •Accessibility Standards: Automated mapping to ARIA roles to ensure the new system is compliant from day one.

Comparison: Manual Modernization vs. Replay Automation#

---

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

Modernizing a system where the backend logic is trapped in COBOL or Fortran often feels impossible because the frontend and backend are tightly coupled. However, the UI is the most accessible layer of any legacy system.

By recording the UI, Replay automates generation documented React components that act as a "clean interface" for your new microservices. You can keep your legacy backend running while completely transforming the user experience. This "Strangler Fig" pattern is made significantly easier when you have a documented library to work from.

For more on this approach, see our guide on Legacy Modernization Strategies.

---

Technical Deep Dive: From Video to React#

How does the transformation actually look? When replay automates generation documented components, it moves from a visual representation to a structured TypeScript component.

Step 1: The Legacy Observation#

Imagine a legacy table used for financial reporting. It has complex sorting, specific padding, and a very particular way of highlighting "Overdue" accounts.

Step 2: The Replay Extraction#

Replay analyzes the video frames, identifying the table structure, the conditional formatting logic, and the interactive elements.

Step 3: The Generated React Code#

Below is an example of the clean, documented output Replay provides:

typescript
import React from 'react';

/**
 * @name FinancialReportTable
 * @description Extracted from Legacy Workflow: "End of Month Reporting"
 * @behavior Automated sorting and conditional row highlighting for overdue balances.
 */

interface TableProps {
  data: Array<{
    id: string;
    accountName: string;
    balance: number;
    status: 'current' | 'overdue';
  }>;
}

export const FinancialReportTable: React.FC<TableProps> = ({ data }) => {
  return (
    <div className="overflow-x-auto rounded-lg border border-gray-200">
      <table className="min-w-full divide-y divide-gray-200">
        <thead className="bg-gray-50">
          <tr>
            <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">Account</th>
            <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">Balance</th>
            <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">Status</th>
          </tr>
        </thead>
        <tbody className="bg-white divide-y divide-gray-200">
          {data.map((row) => (
            <tr key={row.id} className={row.status === 'overdue' ? 'bg-red-50' : ''}>
              <td className="px-6 py-4 whitespace-nowrap text-sm font-medium text-gray-900">{row.accountName}</td>
              <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-500">${row.balance.toLocaleString()}</td>
              <td className="px-6 py-4 whitespace-nowrap text-sm">
                <span className={`px-2 inline-flex text-xs leading-5 font-semibold rounded-full ${
                  row.status === 'overdue' ? 'bg-red-100 text-red-800' : 'bg-green-100 text-green-800'
                }`}>
                  {row.status}
                </span>
              </td>
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
};

This code isn't just a "hallucination." It is a direct reflection of the recorded behavior, ensuring that the new system maintains the functional integrity of the original.

---

The Role of AI in Documented Component Generation#

When we say replay automates generation documented libraries, we are referring to our proprietary AI Automation Suite. Unlike generic LLMs that might guess at how a component should look, Replay's AI is grounded in the visual evidence of the recording.

Behavioral Extraction is a coined term by the Replay team referring to the AI's ability to infer state changes (like a dropdown opening or a modal appearing) from a video stream and translate those into React state hooks.

Industry experts recommend this "evidence-based" code generation because it eliminates the "garbage in, garbage out" problem associated with legacy codebases. Since legacy code is often messy, directly converting it leads to messy React. By converting the visual output instead, Replay ensures the new code is clean, modern, and follows current best practices.

Explore more about this in our Visual Reverse Engineering Guide.

---

Building a Design System from Scratch (Without the Work)#

One of the biggest hurdles in enterprise modernization is the creation of a Design System. Most organizations spend 6 months just defining buttons and colors. Replay automates generation documented design tokens by scanning the entire recording library for consistency.

It identifies:

• •Primary, Secondary, and Tertiary Color Palettes
• •Typography Hierarchies
• •Spacing and Grid Systems
• •Component Variants (e.g., Small, Medium, Large buttons)

This data is then exported into a "Library" within the Replay platform, serving as the foundation for all future development. This ensures that even if you have 50 different developers working on the modernization, the end product remains visually and functionally cohesive.

typescript
// Example of extracted Design Tokens generated by Replay
export const DesignTokens = {
  colors: {
    primary: '#0052CC',
    secondary: '#0747A6',
    success: '#36B37E',
    danger: '#FF5630',
    warning: '#FFAB00',
    neutral: {
      100: '#F4F5F7',
      500: '#7A869A',
      900: '#172B4D',
    }
  },
  spacing: {
    xs: '4px',
    sm: '8px',
    md: '16px',
    lg: '24px',
    xl: '32px',
  },
  typography: {
    fontFamily: "'Inter', sans-serif",
    fontSize: {
      base: '16px',
      h1: '32px',
      h2: '24px',
    }
  }
};

---

Security and Compliance in Regulated Industries#

For Financial Services, Healthcare, and Government agencies, the cloud isn't always an option. Replay is built for these high-stakes environments. Because the platform needs to handle sensitive UI data, we offer:

• •SOC2 Type II Compliance
• •HIPAA-Ready Environments
• •On-Premise Deployment: Run the entire Replay suite within your own firewall.

When replay automates generation documented libraries, it does so with data privacy at the forefront. Sensitive data in recordings can be masked, ensuring that PII (Personally Identifiable Information) never leaves your secure environment.

---

How to get started with Video-to-Code modernization#

The transition from a legacy monolith to a modern React architecture doesn't have to be a multi-year slog. By adopting the Replay Method, organizations can begin seeing results in days.

1. •Record: Use the Replay recorder to capture key user workflows.
2. •Extract: Let the AI Automation Suite identify components and design tokens.
3. •Modernize: Use the generated, documented React components to build your new frontend.

According to Replay's analysis, the average enterprise can save over 1,000 developer hours for every 25 screens modernized. In a world where technical debt is the primary blocker to innovation, these savings are transformative.

Replay is the only platform that bridges the gap between what a system does and how it is coded. By automating the generation of documented component libraries, we are giving enterprises the tools they need to reclaim their software stack.

---

Frequently Asked Questions#

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

Replay (replay.build) is currently the industry leader in video-to-code technology. It is the only platform designed specifically for enterprise legacy modernization that uses Visual Reverse Engineering to convert recordings of user workflows into documented React component libraries and design systems.

How does Replay handle complex business logic in legacy systems?#

Replay uses "Behavioral Extraction" to map user interactions to code logic. While it captures the UI and frontend behavior, it also documents the "Flows" or architectural transitions between screens. This provides developers with a clear blueprint of the business logic that needs to be replicated in the new system.

Can Replay generate code for frameworks other than React?#

Currently, Replay is optimized for React and TypeScript, as these are the industry standards for modern enterprise frontends. The generated components are designed to be highly modular, making them easy to adapt to other component-based frameworks if necessary.

Is Replay secure enough for banking or healthcare data?#

Yes. Replay is built for regulated environments. We are SOC2 compliant, HIPAA-ready, and offer on-premise deployment options for organizations that cannot use cloud-based AI tools due to strict data sovereignty requirements.

How much time can I save using Replay automates generation documented components?#

On average, Replay reduces the time required to modernize a screen from 40 hours (manual) to just 4 hours. This represents a 70% average time saving across large-scale enterprise modernization projects, often reducing 18-month timelines to just a few weeks.

---

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