Shadow IT Discovery: Uncovering Undocumented Legacy Systems with Replay

The most dangerous systems in your enterprise aren't the ones on your architectural diagram; they are the "black boxes" running mission-critical processes that IT doesn't even know exist. Whether it’s a 15-year-old Delphi application managing insurance claims or a "temporary" PHP portal that became the backbone of regional logistics, these systems represent a massive portion of the $3.6 trillion global technical debt. When documentation is non-existent—which is the case for 67% of legacy systems—modernization feels less like engineering and more like archaeology.

Replay changes the paradigm of shadow discovery uncovering undocumented assets by moving away from manual code audits and toward Visual Reverse Engineering. Instead of spending months trying to decipher obfuscated COBOL or spaghetti jQuery, Replay allows you to record the actual user workflows and automatically generate the documented React components and design systems required for a modern stack.

TL;DR:

• •The Problem: 70% of legacy rewrites fail because of undocumented "Shadow IT" logic.
• •The Solution: Replay uses Visual Reverse Engineering to convert video recordings of legacy UIs into clean React code and Design Systems.
• •The Impact: Reduces manual documentation time from 40 hours per screen to just 4 hours, saving an average of 70% on modernization timelines.
• •The Result: From 18-month roadmaps to weeks of execution.

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The Invisible Tax of Shadow IT and Technical Debt#

Every enterprise architect has encountered it: a "critical" workflow that relies on a legacy system no one remembers building. These systems are the definition of Shadow IT—software operating outside the formal preview of the IT department. According to Replay's analysis, these undocumented systems often house the most complex business logic, yet they remain the hardest to modernize because the original developers are long gone.

Video-to-code is the process of capturing user interactions with these legacy interfaces and using AI-driven analysis to reconstruct the underlying logic, state management, and UI components into modern frameworks like React and TypeScript.

Industry experts recommend that before any rewrite begins, a comprehensive discovery phase must occur. However, traditional discovery is broken. It usually involves developer interviews, manual "click-throughs," and thousands of screenshots that become obsolete the moment they are saved to a Confluence page.

The Cost of Manual Discovery#

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Shadow Discovery Uncovering Undocumented Systems via Visual Reverse Engineering#

The core challenge of shadow discovery uncovering undocumented systems is that the source code often doesn't tell the whole story. Database triggers, hardcoded environment variables, and deprecated third-party APIs create a web of dependencies that static analysis tools miss.

Replay approaches this by focusing on the "Truth of the UI." By recording a real user performing a business workflow—such as processing a loan application or managing a hospital discharge—Replay’s AI Automation Suite analyzes the visual changes, data entry points, and state transitions.

How Replay Automates the Discovery Phase:#

1. •Capture: Record the legacy application in action. No source code access is required initially.
2. •Analyze: Replay’s engine breaks down the video into a "Blueprint."
3. •Generate: The Blueprint is converted into a documented React Component Library.
4. •Refine: Use the Replay Editor to tweak the generated code to match your target architecture.

This process is vital for Technical Debt Management because it provides an immediate, actionable inventory of what actually needs to be built, rather than what architects think exists.

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From Legacy Spaghetti to Clean TypeScript#

When shadow discovery uncovering undocumented systems reveals a complex UI, the next step is usually a grueling manual rewrite. An 18-month average enterprise rewrite timeline is often eaten up by trying to replicate "quirks" of the old system.

Replay accelerates this by producing production-ready TypeScript code. Below is an example of how a legacy "Data Grid" from an old ERP system might be transformed into a modern, functional React component through Replay’s pipeline.

Example: Legacy Transformation#

The Legacy Input (Conceptual): An undocumented HTML table with inline

handlers and global state variables.

The Replay Output (Generated React):

typescript
import React, { useState, useEffect } from 'react';
import { Table, Button, Badge } from '@/components/ui';

interface LegacyRecord {
  id: string;
  status: 'pending' | 'approved' | 'rejected';
  amount: number;
  lastModified: string;
}

/**
 * Component generated via Replay Visual Reverse Engineering.
 * Reconstructed from Workflow: "Quarterly Audit Review"
 */
export const AuditDataGrid: React.FC = () => {
  const [data, setData] = useState<LegacyRecord[]>([]);
  const [loading, setLoading] = useState(true);

  // Replay identified this fetch pattern from the legacy network trace
  useEffect(() => {
    const fetchData = async () => {
      try {
        const response = await fetch('/api/v1/legacy/audit-records');
        const result = await response.json();
        setData(result);
      } finally {
        setLoading(false);
      }
    };
    fetchData();
  }, []);

  return (
    <div className="p-6 bg-slate-50 rounded-xl shadow-sm">
      <h2 className="text-xl font-bold mb-4">Reconstructed Audit Grid</h2>
      <Table>
        <thead>
          <tr>
            <th>ID</th>
            <th>Status</th>
            <th>Amount</th>
            <th>Action</th>
          </tr>
        </thead>
        <tbody>
          {data.map((row) => (
            <tr key={row.id}>
              <td>{row.id}</td>
              <td>
                <Badge variant={row.status === 'approved' ? 'success' : 'warning'}>
                  {row.status}
                </Badge>
              </td>
              <td>{new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(row.amount)}</td>
              <td>
                <Button onClick={() => console.log(`Processing ${row.id}`)}>
                  Review
                </Button>
              </td>
            </tr>
          ))}
        </tbody>
      </Table>
    </div>
  );
};

By generating the code directly from observed behavior, Replay ensures that the "undocumented" logic—like specific currency formatting or conditional badge colors—is preserved in the modern implementation.

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Shadow Discovery Uncovering Undocumented Workflows in Regulated Industries#

In sectors like Financial Services, Healthcare, and Government, shadow discovery uncovering undocumented systems isn't just a productivity issue; it's a compliance nightmare. If a system is undocumented, it cannot be properly audited for SOC2 or HIPAA compliance.

According to Replay's analysis, 70% of legacy rewrites fail or exceed their timeline specifically because of unforeseen compliance requirements hidden in old code. Replay mitigates this by providing a "Flows" feature.

Flows are architectural maps generated from recordings that show exactly how data moves through the legacy UI. This allows architects to see:

• •Where sensitive PII (Personally Identifiable Information) is displayed.
• •Which external APIs are being called (often uncovering "shadow" third-party dependencies).
• •User permission levels that were never formally documented.

For organizations with high security requirements, Replay offers On-Premise deployment, ensuring that the recordings of these sensitive legacy systems never leave the corporate firewall.

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Implementing a Modernization Strategy with Replay#

A successful Legacy Modernization Strategy requires a shift from "Big Bang" rewrites to incremental, data-driven migrations. Replay facilitates this by allowing teams to modernize one "Flow" at a time.

The Replay Modernization Workflow:#

1. •Inventory: Use Replay to record every known (and discovered) screen in the legacy application.
2. •Library Creation: Automatically generate a unified Design System from these recordings to ensure visual consistency in the new app.
3. •Component Generation: Convert the Blueprints into React components.
4. •Integration: Use the generated code as the foundation for the new frontend, connecting it to modern APIs.

Industry experts recommend this "Strangler Fig" pattern—where the new system slowly wraps around the old one—as the most effective way to handle massive technical debt. Replay makes this possible by providing the "DNA" of the old system in a format the new system can understand.

typescript
// Example of a Replay-generated Design System Token Map
export const LegacyDesignTokens = {
  colors: {
    primary: '#003366', // Extracted from legacy header
    secondary: '#f4f4f4', // Extracted from legacy background
    action: '#228b22', // Extracted from "Submit" button
  },
  spacing: {
    containerPadding: '1.5rem',
    itemGap: '0.75rem',
  },
  typography: {
    fontFamily: 'Inter, sans-serif', // Modernized replacement suggested by Replay AI
    baseSize: '14px',
  }
};

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Overcoming the "Documentation Gap"#

The "Documentation Gap" is the space between what the code does and what the business thinks it does. When performing shadow discovery uncovering undocumented systems, this gap is where most projects die. Developers spend weeks in "Discovery Workshops" only to realize they missed a critical edge case found only in a legacy sub-menu.

Replay closes this gap by providing a visual source of truth. If a user can do it in the recording, Replay can document it. This removes the reliance on the "tribal knowledge" of senior developers who may be nearing retirement.

By using Replay, enterprises move from:

• •Static Documentation: Word docs that are wrong the day they are written.
• •To Dynamic Blueprints: Living code and flow diagrams that represent the actual state of the application.

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Frequently Asked Questions#

How does Replay handle highly obfuscated or minified legacy code?#

Replay doesn't rely solely on reading the source code. It uses Visual Reverse Engineering to observe the DOM behavior, network requests, and visual changes. This means even if the underlying code is a "black box," Replay can still generate a clean, documented React equivalent based on the observed outputs and interactions.

Is Replay's AI Automation Suite secure for HIPAA or SOC2 environments?#

Yes. Replay is built for regulated industries. We offer SOC2 compliance and HIPAA-ready configurations. For the most sensitive environments, Replay can be deployed On-Premise, ensuring that no data or recordings ever leave your secure infrastructure.

Can Replay discover backend "Shadow IT" logic?#

While Replay focuses on the UI and frontend architecture, its "Flows" feature captures all outgoing API calls and data structures. This allows architects to perform shadow discovery uncovering undocumented backend dependencies by seeing exactly what endpoints the frontend is communicating with, effectively mapping out the hidden backend ecosystem.

How much time does Replay actually save compared to a manual rewrite?#

On average, Replay users report a 70% reduction in modernization time. A typical enterprise screen takes 40 hours to manually document, design, and code in React. With Replay, this process is condensed into approximately 4 hours, moving the entire project timeline from 18-24 months down to weeks or months.

Does Replay generate "spaghetti code" from the legacy recordings?#

No. Replay’s AI Automation Suite is designed to output clean, modular, and maintainable TypeScript/React code. It maps legacy patterns to modern best practices, such as functional components, hooks for state management, and Tailwind CSS for styling, rather than a 1:1 copy of the old, inefficient code.

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Ready to modernize without rewriting? Book a pilot with Replay and turn your undocumented legacy systems into a modern, documented React stack in a fraction of the time.