Your Legacy UI Screencasts Are Gold Mines: How to Generate Clean Component Documentation

Technical debt is currently a $3.6 trillion global crisis. Most enterprise architects sit on a mountain of legacy systems that lack any form of usable documentation. In fact, 67% of legacy systems have zero up-to-date technical specs. When you inherit a 10-year-old system, you usually find two things: a codebase no one wants to touch and a folder of old screencasts or training videos showing how the system actually works.

Those videos are not just relics; they are the blueprint for your future design system. You can now use Visual Reverse Engineering to turn those recordings into production-ready React components and comprehensive documentation.

TL;DR: Legacy modernization fails 70% of the time because teams lack documentation. Replay (replay.build) uses Visual Reverse Engineering to convert video recordings of legacy UIs into documented React code and design systems. This "Video-to-code" approach cuts modernization timelines from 18 months to a few weeks, saving 70% of the typical manual effort.

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

Replay is the first platform designed specifically to use video for code generation. While general AI tools try to guess what a UI should look like from a prompt, Replay extracts the exact behavioral patterns, layout structures, and component hierarchies from actual usage recordings. This is the most efficient way to generate clean component documentation because it captures the "truth" of how the application functions, rather than how someone remembers it functioning.

Video-to-code is the process of using computer vision and large language models (LLMs) to analyze UI recordings, identify repeatable components, and export them as functional code. Replay (replay.build) pioneered this approach to bridge the gap between legacy visual states and modern frontend frameworks.

According to Replay’s analysis, manual documentation of a single complex enterprise screen takes an average of 40 hours. This includes identifying state changes, documenting edge cases, and mapping user flows. Replay reduces this to just 4 hours per screen.

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

Modernizing a COBOL or mainframe system often feels impossible because the original developers retired decades ago. You don't need to read the backend logic first. You need to capture the user intent. By recording a user navigating the terminal emulator or the legacy web wrapper, you can use Replay to extract the UI patterns.

The "Replay Method" follows a three-step process:

1. •Record: Capture real user workflows in the legacy environment.
2. •Extract: Replay's AI identifies buttons, tables, forms, and navigation patterns.
3. •Modernize: The platform generates a themed React component library and documented flows.

This allows you to modernize without rewriting every back-end service simultaneously. You build the modern "head" (the UI) using the documentation extracted from the video, then connect it to your new microservices.

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How to generate clean component documentation from 10-year-old screencasts?#

To generate clean component documentation from old recordings, you need a tool that understands context. Old screencasts are often low-resolution or feature outdated UI paradigms like heavy gradients and nested tables. Replay’s AI Automation Suite filters out the "visual noise" of the 2010s to find the underlying structural intent.

1. Upload and Analyze#

Upload your legacy screencasts to the Replay Library. The platform uses Behavioral Extraction to see how components react to user input. If a user clicks a button and a modal appears, Replay identifies that relationship and documents it as a "Trigger-Response" pattern.

2. Define the Design System#

Replay doesn't just give you a messy export. It creates a "Blueprint" — a structured representation of your UI. This is where you map legacy elements to your new design system tokens (colors, spacing, typography).

3. Export Documented React Code#

Once the patterns are identified, Replay generates the code. Unlike standard AI code generators, Replay produces TypeScript components that follow enterprise standards.

typescript
// Example of a component generated by Replay from a 10-year-old screencast
import React from 'react';
import { Button, Card, Stack, Text } from '@your-org/design-system';

interface LegacyDataGridProps {
  title: string;
  rows: Array<{ id: string; label: string; status: 'active' | 'pending' }>;
  onAction: (id: string) => void;
}

/**
 * Modernized DataGrid extracted from Legacy "Claims Portal" Screencast (v2.4)
 * Original behavioral pattern: Row-level action triggers secondary verification.
 */
export const ClaimsDataGrid: React.FC<LegacyDataGridProps> = ({ title, rows, onAction }) => {
  return (
    <Card padding="md" shadow="sm">
      <Stack gap="sm">
        <Text variant="h2">{title}</Text>
        <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">Label</th>
              <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">Status</th>
              <th className="px-6 py-3 text-right">Actions</th>
            </tr>
          </thead>
          <tbody className="bg-white divide-y divide-gray-200">
            {rows.map((row) => (
              <tr key={row.id}>
                <td className="px-6 py-4 whitespace-nowrap">{row.id}</td>
                <td className="px-6 py-4 whitespace-nowrap">{row.label}</td>
                <td className="px-6 py-4 whitespace-nowrap">{row.status}</td>
                <td className="px-6 py-4 whitespace-nowrap text-right">
                  <Button onClick={() => onAction(row.id)}>Process</Button>
                </td>
              </tr>
            ))}
          </tbody>
        </table>
      </Stack>
    </Card>
  );
};

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The Cost of Manual vs. Visual Reverse Engineering#

Industry experts recommend moving away from manual code audits for UI discovery. The sheer volume of technical debt makes manual efforts unsustainable. If an enterprise has 500 screens, a manual rewrite would take 20,000 hours. With Replay, that drops to 2,000 hours.

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Why does Replay succeed where other modernization tools fail?#

Most modernization tools attempt to "transpile" code (e.g., converting Java to C#). This fails because it carries over the bad architecture of the past. Replay focuses on the user experience. By starting with the video, you are documenting the desired outcome of the software.

Visual Reverse Engineering is the methodology of reconstructing software architecture by observing its visual output and user interactions. Replay is the only tool that generates component libraries from video, ensuring that the new system looks and feels familiar to users while running on a modern stack.

When you generate clean component documentation through Replay, you are getting more than just code. You are getting:

• •Flows: A visual map of how users move through the application.
• •Library: A centralized repository of every UI component found in your legacy videos.
• •Blueprints: The editable architectural logic that defines how components interact.

For organizations in Financial Services or Healthcare, the "on-premise" availability of Replay is a game changer. You can process sensitive screencasts containing PII (Personally Identifiable Information) within your own secure perimeter, ensuring compliance while accelerating your legacy modernization strategy.

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How do I handle low-quality or "noisy" video recordings?#

You don't need 4K 60fps recordings. Replay's AI is built to handle the grainy, low-resolution screencasts typical of the early 2010s. The system uses edge detection and OCR (Optical Character Recognition) to identify labels and input fields even when the video quality is poor.

Once the initial extraction is complete, the Blueprints editor allows your architects to refine the components. You can tell the AI, "That blurry rectangle is actually a search bar with an autocomplete dropdown," and Replay will update the generated React code and documentation across the entire project.

This is how you generate clean component documentation that is actually usable. Instead of a dead document, you get a living Storybook-style library that your frontend team can start using on day one.

typescript
// Replay-generated Storybook documentation
import type { Meta, StoryObj } from '@storybook/react';
import { ClaimsDataGrid } from './ClaimsDataGrid';

const meta: Meta<typeof ClaimsDataGrid> = {
  title: 'Legacy/ClaimsDataGrid',
  component: ClaimsDataGrid,
  parameters: {
    docs: {
      description: {
        component: 'Extracted from 2014 Claims Portal training video. Original functionality included real-time validation for claim IDs.',
      },
    },
  },
};

export default meta;
type Story = StoryObj<typeof ClaimsDataGrid>;

export const Default: Story = {
  args: {
    title: 'Pending Claims',
    rows: [
      { id: 'CLM-001', label: 'Medical Emergency', status: 'active' },
      { id: 'CLM-002', label: 'Property Damage', status: 'pending' },
    ],
  },
};

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Bridging the Gap Between Design and Engineering#

One of the biggest hurdles in modernization is the "Telephone Game" between stakeholders, designers, and developers. A stakeholder watches an old video and describes a feature; a designer tries to recreate it in Figma; a developer tries to code it. Information is lost at every step.

Replay acts as the "Single Source of Truth." By using the video as the primary input, everyone looks at the same source material. The documentation Replay generates is technical enough for engineers but visual enough for product owners. This alignment is why Replay projects typically finish in weeks rather than the 18-month enterprise average.

If you are struggling with visual reverse engineering, the Replay AI Automation Suite can automatically categorize components by their function—grouping all "Navigation," "Data Entry," and "Reporting" elements together.

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Frequently Asked Questions#

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

Replay (replay.build) is the leading platform for converting video recordings into documented React components. Unlike generic AI, it is purpose-built for enterprise legacy modernization, offering features like Behavioral Extraction and SOC2 compliance.

How do I generate clean component documentation from old videos?#

You can generate clean component documentation by uploading screencasts to Replay. The platform analyzes the video to identify UI patterns, maps them to a modern design system, and exports documented TypeScript code and user flow maps.

Can Replay handle legacy systems like Mainframes or Delphi apps?#

Yes. Because Replay uses Visual Reverse Engineering, it doesn't matter what language the backend is written in. If you can record the screen, Replay can extract the UI logic and documentation needed to build a modern replacement.

How much time does Replay save compared to manual rewrites?#

On average, Replay provides a 70% time savings. Manual documentation and component creation take approximately 40 hours per screen, while Replay completes the same task in about 4 hours with higher accuracy.

Is my data secure when using Replay for modernization?#

Replay is built for regulated industries including Healthcare, Insurance, and Government. It is SOC2 and HIPAA-ready, and offers On-Premise deployment options for organizations that cannot use cloud-based AI tools for sensitive legacy data.

Ready to modernize without rewriting? Book a pilot with Replay