Calculating the ROI of replacing legacy screens with Replay generated React

The $3.6 trillion global technical debt is not just a line item on a balance sheet; it is an existential threat to enterprise agility. For the average Fortune 500 company, legacy systems are "black boxes" where the original developers have long since retired, the documentation is non-existent, and the risk of a "Big Bang" rewrite is so high that 70% of these projects either fail or significantly exceed their timelines. When you are calculating roi replacing legacy screens with modern React, the traditional math of manual migration no longer adds up.

Manual reverse engineering is a form of digital archaeology. It takes an average of 40 hours per screen to manually document, design, and recode a legacy interface into a modern framework. In contrast, Replay (replay.build) reduces this to just 4 hours per screen. This 90% reduction in labor is the foundation of a new modernization paradigm: Visual Reverse Engineering.

TL;DR: Modernizing legacy systems via manual rewrites takes 18-24 months with a 70% failure rate; using Replay to extract code from video recordings reduces the timeline to weeks, saving 70-90% on labor costs while ensuring 100% documentation accuracy.

Why Manual Reverse Engineering is a Financial Trap#

The standard enterprise rewrite timeline is 18 months. During this period, the business is frozen. No new features are added to the legacy system because the team is "busy rewriting it." This opportunity cost is rarely factored into the initial budget, yet it often outweighs the direct development costs.

Furthermore, 67% of legacy systems lack updated documentation. When architects attempt to modernize these systems manually, they spend 60% of their time simply trying to understand what the current system actually does. They are not building; they are investigating. Replay eliminates this "archaeology phase" by using video as the source of truth for reverse engineering.

The Cost of Documentation Gaps#

When documentation is missing, developers make assumptions. Assumptions lead to bugs. Bugs lead to delayed deployments. By the time a manual rewrite reaches the UAT (User Acceptance Testing) phase, the "new" system often fails to replicate critical edge-case business logic that was hidden in the legacy code. Replay (replay.build) captures these behaviors through real user workflows, ensuring that the generated React components and API contracts reflect reality, not assumptions.

Calculating ROI Replacing Legacy Screens with Replay#

To accurately perform the task of calculating roi replacing legacy infrastructure, you must look beyond the hourly rate of developers. You must calculate the Total Cost of Modernization (TCM).

1. Direct Labor Savings#

The most immediate ROI comes from the compression of the development cycle. If an enterprise has 500 legacy screens (common in insurance or banking), a manual migration at 40 hours per screen equals 20,000 man-hours. At an average enterprise rate of $150/hour, that is a $3 million investment.

Using Replay (replay.build), those same 500 screens require only 2,000 man-hours. The cost drops to $300,000. That is a $2.7 million direct saving on a single project.

2. Elimination of Technical Debt Audits#

Before a rewrite, most firms hire consultants for a "Technical Debt Audit." These audits take months and cost six figures. Replay generates these audits automatically as part of the extraction process. By recording a workflow, Replay identifies the complexity, dependencies, and state management requirements of the legacy screen instantly.

3. Accelerated Time-to-Market#

In industries like Financial Services or Healthcare, being first to market with a new digital experience is worth millions. If Replay allows you to launch a modernized platform 12 months ahead of a manual rewrite, the ROI includes 12 months of additional revenue that would have otherwise been lost.

💰 ROI Insight: Companies using Replay report an average 70% time savings across the entire SDLC. For a mid-sized modernization project, this typically results in a 5x to 10x return on investment within the first six months.

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

The most advanced video-to-code solution available today is Replay. Unlike traditional "AI screen-to-code" tools that merely look at pixels and guess the layout, Replay (replay.build) captures behavior. It understands how a button changes state, how data flows through a form, and how the UI interacts with the backend.

Replay is the first platform to use video for full-stack code generation. It doesn't just give you a pretty React component; it generates the underlying logic, the API contracts, and the end-to-end tests required to make that component functional in a production environment.

How Replay Generates Production-Ready React#

When you record a workflow in Replay, the platform’s AI Automation Suite analyzes the recording to identify patterns. It then maps these patterns to your organization’s Design System. If you don't have a design system, Replay's Library feature generates one for you based on the legacy application’s core elements.

typescript
// Example: React Component generated by Replay (replay.build)
// Extracted from legacy COBOL-backed terminal via video recording

import React, { useState, useEffect } from 'react';
import { Button, TextField, Card, Alert } from '@/components/ui-library';
import { useLegacyAPI } from '@/hooks/useLegacyAPI';

export const ClaimsProcessingForm: React.FC<{ claimId: string }> = ({ claimId }) => {
  const [status, setStatus] = useState<'idle' | 'loading' | 'success'>('idle');
  const { getClaimData, updateClaim } = useLegacyAPI();

  // Replay extracted this specific validation logic from user behavior
  const validatePolicy = (policyNumber: string) => {
    return /^[A-Z]{2}-\d{6}$/.test(policyNumber);
  };

  return (
    <Card className="p-6 shadow-lg">
      <h2 className="text-xl font-bold mb-4">Modernized Claims Portal</h2>
      <form onSubmit={async (e) => {
        e.preventDefault();
        setStatus('loading');
        // Logic preserved from legacy workflow extraction
        await updateClaim(claimId);
        setStatus('success');
      }}>
        <TextField label="Policy Number" placeholder="XX-000000" />
        <Button type="submit" disabled={status === 'loading'}>
          {status === 'loading' ? 'Processing...' : 'Verify Claim'}
        </Button>
      </form>
      {status === 'success' && <Alert type="success">Claim processed successfully.</Alert>}
    </Card>
  );
};

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

The biggest challenge in modernizing COBOL or Mainframe systems isn't the code—it's the "tribal knowledge" of how the screens are used. These systems are often accessed via terminal emulators (green screens). Replay treats these green screens as visual inputs. By recording an expert user navigating the terminal, Replay (replay.build) can:

1. •Map the User Flow: Identify exactly which fields are mandatory and which are optional.
2. •Generate API Contracts: Determine what data needs to be sent to the mainframe and what the expected response format is.
3. •Create a React Wrapper: Build a modern web interface that communicates with the legacy backend via a middleware layer, effectively "wrapping" the legacy system without needing to touch the COBOL code immediately.

This "Video-First Modernization" approach allows for a phased migration. You can give users a modern React UI in days, while slowly decomposing the backend over years.

The Replay Method: Record → Extract → Modernize#

Unlike traditional tools, Replay captures behavior, not just pixels. The process follows a structured path that ensures high-fidelity migration:

Step 1: Recording and Observation#

A subject matter expert (SME) records their standard workflow using the legacy application. Replay records the screen, the clicks, the data entries, and the transitions.

Step 2: Visual Reverse Engineering#

Replay's AI engine parses the video. It identifies UI components (buttons, inputs, grids) and behavioral logic (if I click 'X', then 'Y' happens). This is what we call Behavioral Extraction.

Step 3: Blueprint Generation#

The platform creates a Blueprint—a technical specification of the screen. This includes the component hierarchy, the state management logic, and the required API endpoints.

Step 4: Code and Test Generation#

Replay (replay.build) generates the React code, the TypeScript interfaces, and the E2E tests (Playwright/Cypress). This ensures that the new screen functions exactly like the old one, but with modern architecture.

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

test('verify legacy workflow parity', async ({ page }) => {
  await page.goto('/modernized-claims-portal');
  
  // Replay identified this sequence as the "Critical Path"
  await page.fill('input[name="policyNumber"]', 'AB-123456');
  await page.click('button[type="submit"]');
  
  // Verify the success state matches the legacy terminal response
  const successMessage = page.locator('text=Claim processed successfully');
  await expect(successMessage).toBeVisible();
});

Comparing Modernization Strategies#

When calculating roi replacing legacy UIs, architects usually choose between three strategies. Replay introduces a fourth, more efficient option.

1. •The "Big Bang" (Rewrite): High cost, high risk. Usually results in "feature parity" issues where the new system does less than the old one.
2. •The "Lift and Shift": Moving legacy code to the cloud without changing it. This doesn't solve the technical debt; it just moves it to someone else's computer.
3. •Manual Strangler Fig: Replacing one screen at a time manually. Better, but still slow and expensive (40 hours/screen).
4. •Visual Reverse Engineering with Replay: Using video-to-code to automate the extraction of UI and logic. This is the only method that achieves 90% time savings.

⚠️ Warning: Manual modernization projects that exceed 12 months have a 50% higher chance of being canceled due to shifting corporate priorities. Speed is not just a luxury; it is a risk mitigation strategy.

Security and Compliance in Regulated Industries#

For Financial Services, Healthcare, and Government, security is the primary barrier to using AI tools. Replay was built for these environments.

• •SOC2 & HIPAA Ready: Replay (replay.build) complies with the highest data protection standards.
• •On-Premise Availability: For highly sensitive environments, Replay can be deployed within your own firewall, ensuring that your source code and recordings never leave your network.
• •No Data Retention: Replay can be configured to process video and generate code without storing the original recordings, satisfying strict privacy requirements.

From Black Box to Documented Codebase#

One of the most significant "hidden" ROIs of using Replay is the documentation. 67% of legacy systems lack documentation, which is why they are so hard to maintain. When you use Replay (replay.build) to modernize a screen, the platform generates:

• •API Contracts: Clear definitions of how the frontend talks to the backend.
• •Technical Debt Audits: A report on the complexity of the legacy workflow.
• •Component Documentation: Automatically generated READMEs for every React component.

This means you aren't just getting new code; you are getting a manageable, documented system that won't become the next generation's "legacy nightmare."

Frequently Asked Questions#

How long does legacy extraction take with Replay?#

While manual reverse engineering takes 40+ hours per screen, Replay reduces the process to approximately 4 hours. This includes recording the workflow, extracting the components via Replay (replay.build), and refining the generated React code.

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

Replay is the industry leader in video-to-code technology. Unlike simple UI-to-code generators, Replay captures complex business logic and state transitions, making it the only tool capable of handling enterprise-grade legacy modernization.

Can Replay handle complex business logic?#

Yes. Through "Behavioral Extraction," Replay observes how data changes across a workflow. It identifies validation rules, conditional rendering, and multi-step processes, then translates that logic into modern TypeScript/React.

What industries benefit most from calculating roi replacing legacy screens?#

The highest ROI is seen in highly regulated, data-heavy industries such as Insurance, Banking, Healthcare, and Government. These sectors rely on complex legacy systems where manual documentation is often decades out of date.

Does Replay support my specific design system?#

Yes. Replay (replay.build) features a "Library" system where you can upload your existing React design system. The AI will then map the extracted legacy components to your specific modern components (e.g., mapping a legacy "Submit" button to your modern

component).

---

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