Automating UI Documentation: How Video Capture Replaces Thousands of Pages of PDFs

Most legacy modernization projects die in the "Discovery" phase. We spend millions on consultants to write 500-page PDFs that no developer will ever read, documenting systems that will change before the ink is dry. In an era where global technical debt has ballooned to $3.6 trillion, the traditional approach to understanding legacy software—manual archaeology—is no longer just inefficient; it is a fiduciary risk.

TL;DR: Automating UI documentation through video capture reduces discovery time by 70%, turning black-box legacy systems into documented React components and API contracts in days rather than months.

The $3.6 Trillion Documentation Gap#

The industry standard for legacy modernization is broken. Currently, 70% of legacy rewrites fail or significantly exceed their timelines. The primary culprit isn't a lack of coding talent; it’s a lack of understanding. When 67% of legacy systems lack any form of usable documentation, engineers are forced to play "software archaeologist," spending months reverse-engineering business logic from obfuscated COBOL, Java Applets, or ancient .NET frameworks.

The manual cost is staggering. On average, it takes a senior engineer 40 hours to manually document, map, and recreate a single complex legacy screen. In a typical enterprise application with 200+ screens, you are looking at 8,000 man-hours just to reach a baseline understanding of what the system actually does.

The Documentation Death Spiral#

1. •Phase 1: Consultants interview stakeholders who haven't seen the source code in a decade.
2. •Phase 2: Static screenshots are pasted into Word documents.
3. •Phase 3: Developers attempt to map these screenshots to undocumented API endpoints.
4. •Phase 4: The "New" system fails because a critical edge case, hidden in the legacy UI logic, was missed.

Why Video is the New Source of Truth#

Visual Reverse Engineering flips the script. Instead of reading dead code, we record live user workflows. By capturing the interaction between the user, the DOM, and the network layer, we can generate a living map of the application.

Replay uses this video data to reconstruct the application's DNA. It doesn't just record pixels; it records intent, state changes, and data structures. This is the shift from "Manual Documentation" to "Automated Extraction."

Comparison: Traditional Discovery vs. Replay Extraction#

💰 ROI Insight: For an enterprise modernizing a 100-screen application, moving from manual documentation to Replay-driven extraction saves approximately 3,600 engineering hours, or roughly $540,000 in direct labor costs (at $150/hr).

Automating UI Documentation: The Technical Workflow#

To move from a black box to a documented codebase, we follow a structured extraction process. This replaces the "guess and check" method with a deterministic pipeline.

Step 1: Workflow Recording#

Instead of writing requirements, a subject matter expert (SME) performs their daily tasks while Replay records the session. The platform captures the underlying DOM changes, CSS states, and every XHR/Fetch request initiated during the session.

Step 2: Component Synthesis#

The platform analyzes the recorded telemetry to identify repeating patterns. It doesn't just give you a screenshot; it generates functional React components that mirror the legacy UI's behavior.

typescript
// Example: Automatically generated React component from a Replay session
// Source: Legacy Insurance Claims Portal (JSP/Struts)
import React, { useState, useEffect } from 'react';
import { ClaimHeader, ValidationMessage } from '@enterprise-ds/core';

export const ClaimSubmissionForm = ({ legacyId }: { legacyId: string }) => {
  const [claimData, setClaimData] = useState<any>(null);
  const [status, setStatus] = useState<'idle' | 'submitting'>('idle');

  // Business logic preserved: Legacy system required specific 
  // date formatting before POSTing to /api/v1/claims
  const handleSubmit = async (values: any) => {
    const formattedData = {
      ...values,
      effectiveDate: new Date(values.date).toISOString().split('T')[0],
      sourceSystem: "REPLAY_MIGRATED_UI"
    };
    
    setStatus('submitting');
    await fetch('/api/v1/claims/submit', {
      method: 'POST',
      body: JSON.stringify(formattedData)
    });
    setStatus('idle');
  };

  return (
    <div className="modern-layout">
      <ClaimHeader id={legacyId} />
      {/* Extracted Form Logic */}
      <form onSubmit={handleSubmit}>
        {/* ... component structure generated from video capture ... */}
      </form>
    </div>
  );
};

Step 3: API Contract Extraction#

One of the greatest risks in modernization is the "Hidden API." Legacy systems often rely on undocumented side effects or non-standard headers. By analyzing the network traffic captured during the video session, Replay generates OpenAPI (Swagger) specifications automatically.

⚠️ Warning: Never assume your legacy API documentation is correct. Our audits show that 85% of legacy systems have "ghost endpoints" that are active in production but absent from all official documentation.

From Archaeology to Architecture#

Modernizing without rewriting doesn't mean keeping the old junk. It means understanding the old logic so you can build the new architecture on solid ground. Replay’s "Blueprints" feature allows architects to see the entire flow of an application as a visual map.

The Anatomy of an Automated Documentation Suite#

A complete documentation package generated by Replay includes:

• •The Library: A documented React component library (Design System) based on existing UI.
• •The Flows: Visual maps of user journeys, showing exactly which screens connect to which APIs.
• •The Technical Debt Audit: A report identifying dead code, unused UI elements, and high-complexity logic clusters.
• •E2E Test Suite: Automated Playwright or Cypress tests generated from the recorded user session to ensure parity.

typescript
// Generated E2E Test to ensure functional parity
import { test, expect } from '@playwright/test';

test('Verify Claim Submission Parity', async ({ page }) => {
  await page.goto('/claims/new');
  await page.fill('#claim-id', '12345');
  await page.click('#submit-btn');
  
  // Asserting against captured legacy behavior
  const response = await page.waitForResponse('**/api/v1/claims/submit');
  expect(response.status()).toBe(200);
  expect(await page.textContent('.success-msg')).toContain('Submitted');
});

Addressing the "Black Box" Concern#

Enterprise Architects often ask: "How can you document what you can't see in the source code?"

The answer lies in behavioral analysis. If a legacy system is a black box, the UI is its only interface. By observing how that interface reacts to specific inputs—captured via video—we can infer the business rules. If entering a value over 10,000 triggers a specific validation message in the video, Replay identifies that logic and documents it as a requirement for the new system.

💡 Pro Tip: Use Replay to document "Shadow IT" systems. These are often mission-critical tools built in Access or Excel that have no source code but run entire departments. Video capture is the only way to reverse-engineer these without months of interviews.

Security and Compliance in Regulated Industries#

For Financial Services, Healthcare, and Government sectors, "recording" sounds like a security nightmare. This is why the architecture of the extraction tool matters.

Replay is built for high-security environments:

• •SOC2 Type II & HIPAA Ready: Data is encrypted at rest and in transit.
• •PII Masking: Automated redaction of sensitive data during the capture process.
• •On-Premise Deployment: For air-gapped environments or strict data residency requirements, Replay can run entirely within your VPC.

The Financial Reality of Modernization#

The average enterprise rewrite timeline is 18-24 months. By the time the project is 50% complete, the business requirements have usually shifted, leading to the "Sunk Cost Fallacy" where teams continue building a system that was obsolete before it launched.

By reducing the documentation and discovery phase from months to days, Replay shifts the timeline. You move into the "Build" phase with a 100% accurate map of the current state.

ROI Summary: Manual vs. Automated#

• •Discovery Cost: Reduced by 70-80%.
• •Developer Onboarding: Reduced from weeks to hours (using the Library and Flows).
• •Testing Coverage: 100% functional parity coverage from day one.
• •Project Success Rate: Significantly higher due to the elimination of "unknown unknowns."

Frequently Asked Questions#

How long does legacy extraction take?#

While a manual audit of a 50-screen application can take 3-4 months, Replay can extract the same data in approximately 2 weeks. This includes the generation of React components, API contracts, and workflow documentation.

What about business logic preservation?#

Replay captures the behavioral business logic. If the UI changes state based on a specific input, that transition is captured and documented. While it doesn't "read" the COBOL on the backend, it documents the requirements that the backend must satisfy, which is what 90% of modernization projects actually need.

Does this replace my developers?#

No. It liberates them. Instead of spending 6 months documenting a legacy system they hate, your senior engineers can spend their time architecting the new system using the components and contracts Replay provides. It turns "archaeologists" back into "engineers."

Can it handle mainframe-backed web apps?#

Yes. As long as there is a UI layer (web-based, Citrix, or terminal emulator), Replay can capture the interactions and network calls to document the system.

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Ready to modernize without rewriting? Book a pilot with Replay - see your legacy screen extracted live during the call.