From 40 Hours per Screen to 4: Accelerating UI Extraction for Legacy Portals

The average enterprise architect treats a legacy portal like a crime scene: don't touch anything, don't move the wires, and try to piece together what happened five years before you joined the company. With 67% of legacy systems lacking any meaningful documentation, we’ve been forced into a manual process of "software archaeology" that is killing enterprise velocity.

The math is brutal. In a typical modernization project, it takes an average of 40 hours per screen to manually document, design, and recode a legacy interface into a modern framework. When you're staring down a portal with 200+ screens, you aren't looking at a project; you're looking at a multi-year death march. This is why 70% of legacy rewrites fail or exceed their timelines, contributing to a staggering $3.6 trillion in global technical debt.

We need to stop rewriting from scratch and start understanding what we already have. By moving from manual reconstruction to visual reverse engineering, we can compress that 40-hour window down to 4 hours.

TL;DR: Visual reverse engineering allows teams to extract legacy UI and logic directly from user sessions, reducing modernization timelines by 70% and turning "black box" systems into documented React codebases in days rather than months.

The Cost of Manual Reconstruction#

The industry has traditionally relied on the "Big Bang" rewrite. We hire a fleet of developers to sit with subject matter experts (SMEs), watch them use an old Silverlight or JSP portal, and try to guess the business logic hidden behind the buttons.

This approach is fundamentally flawed because it relies on human memory and manual translation. When a developer spends 40 hours on a single screen, they are spending 36 of those hours just trying to figure out what the original code was supposed to do.

💰 ROI Insight: For a 100-screen enterprise portal, manual modernization costs approximately $800,000 (assuming $100/hr). Using Replay, that cost drops to $80,000, representing a 90% reduction in direct labor costs.

Why "Software Archaeology" Fails#

When we talk about the "40-hour screen," we’re talking about the hidden tax of technical debt. Most legacy portals in Financial Services or Healthcare aren't just "old UI"—they are layers of undocumented business rules.

1. •The Documentation Gap: 67% of systems have no living documentation. The original architects are gone.
2. •The Logic Trap: Business logic is often buried in the UI layer (e.g., specific validation rules triggered by obscure DOM events).
3. •The Integration Nightmare: Legacy systems often rely on undocumented side-effects in global state or local storage that are missed during a manual rewrite.

Replay changes the source of truth. Instead of relying on outdated Word docs or SME interviews, Replay uses the video of a real user workflow as the source of truth for reverse engineering.

From Video to Production-Ready React#

The core shift is moving from "writing code" to "extracting intent." When you record a workflow in Replay, the platform isn't just capturing pixels; it's capturing the DOM state, the API calls, the data transformations, and the component hierarchy.

Here is what a typical manual reconstruction looks like versus the automated output from Replay.

Manual Reconstruction (The 40-Hour Way)#

Developers have to manually inspect elements, map CSS, and guess at state management.

typescript
// Manual attempt to recreate a legacy insurance claim form
// Time spent: 12 hours just for the basic layout and validation
export const LegacyClaimForm = () => {
  const [status, setStatus] = useState('pending');
  
  // Hardcoded logic guessed from watching the old app
  const handleValidate = (val: string) => {
    if (val.length > 10 && val.startsWith('N-')) { 
       // Is this right? No one knows.
       return true;
    }
    return false;
  }

  return (
    <div className="old-container-styles">
      {/* Manually recreated components */}
    </div>
  );
}

Extracted via Replay (The 4-Hour Way)#

Replay extracts the actual component structure, styles, and logic, then maps them to your modern Design System.

typescript
// Generated component from Replay video extraction
// Logic preserved from actual runtime execution
import { Button, TextField, Card } from "@your-org/design-system";

export function MigratedClaimPortal({ initialData }) {
  // Business logic extracted from recorded DOM events
  const validatePolicyFormat = (id: string) => {
    // Replay identified this regex from legacy script execution
    const policyRegex = /^[A-Z]{1}-\d{8}$/;
    return policyRegex.test(id);
  };

  return (
    <Card title="Policy Management">
      <TextField 
        label="Policy ID"
        defaultValue={initialData.policyId}
        onValidate={validatePolicyFormat}
      />
      {/* E2E Test IDs automatically generated for the extracted flow */}
      <Button data-testid="submit-claim-flow-step-2">
        Continue to Coverage
      </Button>
    </Card>
  );
}

The 4-Step Accelerated Extraction Workflow#

Modernizing a legacy portal shouldn't feel like a guessing game. By using Replay’s AI Automation Suite, we follow a repeatable, industrial-scale process.

Step 1: Workflow Recording#

Instead of reading code, we record experts. A user performs a standard business process (e.g., "Onboard a new patient" or "Process a wire transfer"). Replay captures the "Black Box" behavior—every network request, every state change, and every UI transition.

Step 2: Visual Mapping (The Library)#

Replay’s Library feature identifies recurring UI patterns. It sees that the legacy "Blue Button" used across 50 screens is actually a single functional component. We map these legacy elements to modern React components in your new Design System.

💡 Pro Tip: Don't try to map every pixel. Map the intent. A legacy table with 50 attributes should be mapped to your modern

text

DataTable

component with the same data bindings.

Step 3: Blueprint Generation#

Using the Blueprints editor, the platform generates the application architecture. It creates the API contracts (OpenAPI/Swagger) based on the actual traffic recorded during the session. This eliminates the "broken contract" bug that plagues 80% of manual rewrites.

Step 4: Technical Debt Audit & Cleanup#

Replay doesn't just copy the mess. It performs an automated Technical Debt Audit, identifying redundant logic and dead code paths that were never triggered during the recordings. You get a clean, documented React codebase that is SOC2 and HIPAA compliant by design.

Solving the "Black Box" Problem in Regulated Industries#

In Financial Services and Government, you can't just "move fast and break things." You have strict compliance requirements. This is why Replay is built for high-security environments, offering On-Premise deployment options.

• •API Preservation: Replay generates E2E tests that compare the legacy output with the new system output to ensure 100% parity.
• •Audit Trails: Every line of generated code is linked back to the original recording—the "Source of Truth."
• •Security: No data leaves your environment if you choose the On-Premise or VPC deployment.

⚠️ Warning: The biggest risk in modernization isn't the technology—it's the "Knowledge Gap." When you lose the "why" behind a legacy feature, you introduce regression risks that can cost millions in downtime.

Real-World Impact: The 18-Month Barrier#

We recently worked with a global insurance provider stuck in a 24-month rewrite of their claims portal. After 18 months, they had only migrated 15% of the screens. The complexity of the legacy Java applets was too high for manual documentation.

By implementing Replay, they:

• •Recorded all 120 user workflows in 2 weeks.
• •Extracted 85% of the UI components into a clean React library.
• •Reduced the remaining timeline from 2 years to 4 months.
• •Result: They hit their board-mandated deadline with a fully documented system.

Frequently Asked Questions#

How long does legacy extraction actually take?#

While it varies by complexity, we typically see a 10x speed improvement. A screen that takes a senior developer 40 hours to manually audit, document, and recreate in React takes about 4 hours using Replay's extraction and mapping tools.

What about business logic preservation?#

Replay captures the behavioral logic of the UI. For complex backend calculations, Replay generates the API contracts and E2E tests needed to ensure your new frontend communicates perfectly with existing (or refactored) microservices. It bridges the gap between the user's intent and the backend's response.

Does this work with any legacy framework?#

Yes. Because Replay operates on the visual and network layer (Visual Reverse Engineering), it doesn't matter if the underlying system is COBOL-backed, a JSP monolith, or a Silverlight application. If it runs in a browser or a terminal emulator, Replay can extract it.

How does this handle technical debt?#

Replay's AI Automation Suite identifies "Dead UI"—features that are in the code but never used in real-world workflows. This allows architects to make data-driven decisions on what to migrate and what to retire, shrinking the codebase by an average of 30%.

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