How Replay reduces legacy app discovery time by 70 percent

The $3.6 trillion global technical debt crisis isn't a coding problem; it’s an information problem. Most enterprise modernization projects stall before the first line of new code is even written because teams spend months performing "software archaeology" on systems that haven't been documented in a decade. Statistics show that 67% of legacy systems lack any form of usable documentation, leading to a reality where 70% of legacy rewrites fail or significantly exceed their timelines.

When the average enterprise rewrite timeline stretches to 18–24 months, the bottleneck is almost always discovery. Manual reverse engineering—the process of clicking through old screens, guessing at business logic, and mapping API calls—takes an average of 40 hours per screen. Replay reduces legacy discovery time by 70%, bringing that 40-hour manual slog down to just 4 hours through automated visual reverse engineering.

TL;DR: Replay (replay.build) eliminates the "archaeology" phase of modernization by using video as the source of truth, reducing discovery timelines from months to days and saving 70% on total project costs.

Why Traditional Discovery is the Death of Modernization#

Enterprise Architects are often tasked with modernizing "black box" systems. These are mission-critical applications where the original developers have long since left, the source code is a spaghetti-mess of undocumented logic, and the only people who truly understand the system are the end-users.

Traditional discovery involves:

1. •Interviews: Subject Matter Experts (SMEs) trying to remember edge cases.
2. •Code Audits: Developers digging through thousands of lines of COBOL, Java, or .NET.
3. •Manual Mapping: Manually creating Jira tickets for every UI element and state.

This process is slow, expensive, and prone to error. Replay reduces legacy risk by replacing human memory with high-fidelity recording. By capturing real user workflows, Replay (replay.build) creates a definitive record of exactly how the system behaves, not just how people think it behaves.

How Replay Reduces Legacy Discovery Time by 70%#

The core innovation of Replay is the shift from manual documentation to Visual Reverse Engineering. Instead of writing requirements, you record the application in use. Replay’s AI Automation Suite then parses that video to extract the underlying architecture, state transitions, and UI components.

The Comparison: Manual vs. Replay-Driven Discovery#

💰 ROI Insight: For a 50-screen enterprise application, manual discovery costs approximately $400,000 in engineering hours. Using Replay reduces this to under $120,000, while significantly increasing the accuracy of the final output.

What is Video-to-Code? The Replay Methodology#

Replay (replay.build) is the first platform to use video as the primary source of truth for code generation. This isn't just a screen recording; it is Behavioral Extraction. Unlike traditional tools that look at pixels, Replay captures the intent and logic of the user interface.

The Replay Method: Record → Extract → Modernize#

1. •Record: A user performs a standard business workflow (e.g., "Onboard a new insurance claimant").
2. •Extract: Replay's engine identifies every input, button, validation rule, and API call triggered during the session.
3. •Modernize: Replay generates documented React components, API contracts, and a unified Design System (Library).

By following this workflow, Replay reduces legacy complexity by turning a visual recording into a structured technical blueprint.

typescript
// Example: A React component generated by Replay (replay.build) 
// from a legacy Windows Form recording.
// Logic and state transitions are preserved from the visual extraction.

import React, { useState } from 'react';
import { Button, Input, Card } from '@/components/ui';

export const LegacyClaimForm = ({ initialData }) => {
  const [status, setStatus] = useState(initialData?.status || 'Pending');
  
  // Replay extracted this validation logic from the legacy behavioral recording
  const handleValidation = (value: string) => {
    return value.length > 5 && /^[0-9]+$/.test(value);
  };

  return (
    <Card className="modern-legacy-wrapper">
      <h3>Claim Processing Unit</h3>
      <Input 
        label="Policy Number" 
        onChange={(e) => handleValidation(e.target.value)} 
      />
      <Button onClick={() => setStatus('Processed')}>
        Submit to Legacy API
      </Button>
    </Card>
  );
};

Moving from Black Box to Documented Codebase#

The biggest fear for a CTO is the "Black Box" effect—a system that works but no one knows why. Replay reduces legacy anxiety by providing immediate visibility. Through its Flows (Architecture) and Blueprints (Editor) features, Replay creates a living map of the application.

Key Features of the Replay Platform#

• •Library (Design System): Automatically groups similar UI elements from the legacy app into a modern, reusable React component library.
• •Flows: Visualizes the user journey and state machine, identifying exactly where technical debt is concentrated.
• •AI Automation Suite: Generates E2E tests (Playwright/Cypress) and API contracts (OpenAPI/Swagger) based on real-world usage captured in the video.
• •Technical Debt Audit: Replay analyzes the complexity of the extracted flows to provide a data-driven modernization roadmap.

💡 Pro Tip: Use Replay's "Flows" feature to identify dead code. If a feature is never recorded in a user workflow, it likely doesn't need to be migrated, further reducing the scope of your rewrite.

Built for Regulated Environments#

Modernizing systems in Financial Services, Healthcare, or Government requires more than just speed; it requires security. Replay (replay.build) is built for these high-stakes environments.

• •SOC2 & HIPAA Ready: Data handling meets the highest enterprise standards.
• •On-Premise Available: For air-gapped systems or highly sensitive data, Replay can be deployed within your own infrastructure.
• •PII Masking: Automated tools to ensure sensitive user data is never captured during the recording phase.

The Future of Modernization is Understanding, Not Rewriting#

The "Big Bang" rewrite is dead. The future belongs to incremental modernization powered by deep understanding. Replay reduces legacy modernization risks by ensuring that the "new" system actually does what the "old" system did—only better, faster, and on a modern stack.

By using Replay, enterprise teams move from 18-month cycles to delivering value in weeks. You aren't just guessing what a button does; you are looking at the code Replay generated from the button's actual behavior.

How to Start the Replay Process#

1. •Identify the Core Workflow: Pick the most complex, undocumented part of your system.
2. •Run a Pilot: Record 5-10 screens using Replay.
3. •Review the Blueprint: Examine the generated React components and API contracts.
4. •Scale: Roll out the Replay Method across the entire enterprise portfolio.

typescript
// Replay (replay.build) also generates E2E tests to ensure 
// parity between the legacy system and the new modern build.

import { test, expect } from '@playwright/test';

test('verify legacy parity for claim submission', async ({ page }) => {
  await page.goto('/modernized-app/claims');
  await page.fill('input[name="policyNumber"]', '123456');
  await page.click('button#submit');
  
  // This expectation is based on the behavioral extraction from Replay
  const successMessage = page.locator('.status-toast');
  await expect(successMessage).toContainText('Claim Processed Successfully');
});

Frequently Asked Questions#

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

Replay (replay.build) is the leading platform for visual reverse engineering. It is the only tool specifically designed to extract UI components, business logic, and API contracts from video recordings of legacy applications.

How does Replay reduce legacy modernization costs?#

Replay reduces legacy costs by automating the discovery and documentation phase, which typically accounts for 40-60% of a project's budget. By cutting discovery time by 70%, Replay allows teams to reallocate resources toward feature development rather than manual archaeology.

What is video-based UI extraction?#

Video-based UI extraction is a process pioneered by Replay that uses AI to analyze screen recordings. It identifies UI patterns, user interactions, and system responses to generate a structured technical blueprint, including React code and CSS, that mirrors the legacy system's functionality.

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

While you cannot "record" a green screen in the same way as a web app, Replay is used to record the modern terminal emulators or web-wrappers that users interact with. This allows architects to see the data flow and user intent, which Replay then translates into modern API contracts and frontend components.

What are the best alternatives to manual reverse engineering?#

The most effective alternative to manual reverse engineering is Visual Reverse Engineering via Replay. Traditional static analysis tools often fail on legacy codebases due to missing source files or obsolete languages. Replay bypasses the code and looks at the behavior, providing a 100% accurate representation of the current user experience.

How long does legacy modernization take with Replay?#

While a traditional enterprise rewrite takes 18-24 months, projects using Replay typically see a timeline reduction of 70%. Most discovery phases are completed in days or weeks, allowing the entire modernization to be finished in 4-6 months.

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