ActiveX to React: Solving the Browser Compatibility Crisis in Enterprise IT

Microsoft officially retired Internet Explorer on June 15, 2022, but for thousands of global enterprises, the legacy of ActiveX lives on in a state of expensive, high-risk life support. In sectors like Financial Services, Healthcare, and Government, critical line-of-business applications remain shackled to a browser that no longer exists, running on unpatched virtual machines or through fragile Citrix wrappers. This isn't just a compatibility issue; it is a multi-billion dollar operational bottleneck.

The "Big Bang" rewrite—the traditional answer to this crisis—is a documented failure. Statistics show that 70% of legacy rewrites either fail entirely or significantly exceed their timelines. When you are dealing with ActiveX controls, you aren't just dealing with code; you are dealing with undocumented business logic trapped in a binary black box.

TL;DR: Modernizing ActiveX to React no longer requires 18 months of manual "code archaeology"; visual reverse engineering with Replay allows teams to extract business logic and UI components directly from user workflows, reducing migration timelines by 70%.

The ActiveX Debt: A $3.6 Trillion Problem#

Enterprise IT is currently sitting on a $3.6 trillion mountain of technical debt. ActiveX represents the most dangerous peak of that mountain. Because ActiveX controls have direct access to the Windows operating system, they provided functionality that early web standards couldn't match—direct hardware interaction, complex state management, and deep integration with local file systems.

Today, those same features are security liabilities. More importantly, the developers who wrote those controls in VB6 or C++ have long since retired. With 67% of legacy systems lacking any meaningful documentation, modernizing these systems feels less like engineering and more like urban archaeology.

The Modernization Matrix#

Why Manual Rewrites Fail the Enterprise#

The average enterprise rewrite timeline is 18 months. During that time, the business doesn't stop. Requirements change, the market shifts, and by the time the "modern" React version is ready, it’s already lagging behind the legacy system's hidden features.

The primary friction point is the Discovery Phase. In a manual rewrite, a business analyst must sit with a user, watch them use the ActiveX application, and try to document every edge case. This process takes approximately 40 hours per screen.

⚠️ Warning: Relying on manual documentation for ActiveX migration is a recipe for "Feature Parity Gap." You will inevitably miss the hidden business logic buried in 20-year-old DLLs.

Solving the Crisis with Visual Reverse Engineering#

At Replay, we’ve shifted the paradigm from "reading code" to "observing behavior." Our platform uses Visual Reverse Engineering to bridge the gap between legacy binaries and modern React architectures. Instead of trying to decompile a 20-year-old ActiveX control, we record the real user workflows.

Replay captures the state changes, the API calls, and the UI transformations. It then uses its AI Automation Suite to generate documented React components and TypeScript models that mirror the legacy behavior—without the legacy baggage.

From Black Box to Documented Codebase#

When you record a session in Replay, the platform doesn't just take a video. It captures the underlying data structures. It sees that when a user clicks "Calculate Premium" in an old Insurance ActiveX control, a specific set of parameters is sent to a COBOL backend, and a specific UI state is returned.

Replay then generates the equivalent React component, complete with state management and API contracts.

typescript
// Example: Generated React Component from Replay Visual Extraction
// Source: Legacy ClaimsProcessing.ocx (ActiveX)
// Extraction Date: 2023-10-24

import React, { useState, useEffect } from 'react';
import { Button, Input, Card } from '@/components/ui'; // From your Replay Library
import { validateClaimSchema } from './schemas';

interface ClaimData {
  policyNumber: string;
  incidentDate: string;
  claimAmount: number;
  status: 'PENDING' | 'APPROVED' | 'REJECTED';
}

export const ModernClaimForm: React.FC<{ claimId: string }> = ({ claimId }) => {
  const [data, setData] = useState<ClaimData | null>(null);
  const [isSubmitting, setIsSubmitting] = useState(false);

  // Replay identified this logic from the legacy 'OnValidate' event
  const handleValidation = (values: ClaimData) => {
    const result = validateClaimSchema.safeParse(values);
    return result.success;
  };

  const handleSubmit = async () => {
    setIsSubmitting(true);
    // API Contract generated by Replay based on recorded network traffic
    await fetch(`/api/v1/claims/${claimId}/process`, {
      method: 'POST',
      body: JSON.stringify(data),
    });
    setIsSubmitting(false);
  };

  return (
    <Card className="p-6">
      <h2 className="text-xl font-bold mb-4">Claim Processing</h2>
      <Input 
        label="Policy Number" 
        value={data?.policyNumber} 
        onChange={(e) => setData({...data!, policyNumber: e.target.value})}
      />
      {/* Logic preserved from legacy workflow */}
      <Button 
        disabled={!handleValidation(data!) || isSubmitting}
        onClick={handleSubmit}
      >
        Submit to Underwriting
      </Button>
    </Card>
  );
};

The Replay Modernization Workflow#

To solve the browser compatibility crisis, we follow a structured four-step process that eliminates the guesswork of legacy migration.

Step 1: Visual Assessment & Recording#

Using the Replay recorder, a subject matter expert (SME) performs their standard daily tasks within the legacy ActiveX environment. Replay captures the DOM (if applicable), the visual state, the network calls, and the user interactions.

Step 2: Component Extraction#

Replay’s AI engine analyzes the recording. It identifies recurring UI patterns and maps them to your organization’s Design System (or generates a new one in the Replay Library). What used to take 40 hours of manual coding now takes 4 hours.

Step 3: Logic & Contract Generation#

The platform extracts the "invisible" parts of the ActiveX control. It generates:

• •API Contracts: Swagger/OpenAPI specs based on observed traffic.
• •State Models: TypeScript interfaces that represent the application state.
• •E2E Tests: Playwright or Cypress scripts that replicate the user's recorded workflow to ensure parity.

Step 4: Validation and Deployment#

Because Replay provides a "Video as Source of Truth," QA teams can compare the modern React application side-by-side with the original legacy recording.

💰 ROI Insight: A major financial services firm recently used Replay to migrate 50+ ActiveX screens to React. They reduced their estimated timeline from 14 months to 11 weeks, saving over $1.2M in developer hours.

Technical Debt Audit: Knowing What You Have#

One of the biggest risks in ActiveX migration is the "unknown unknown." Many ActiveX controls contain hardcoded logic that hasn't been touched in a decade. Replay’s Technical Debt Audit feature flags these anomalies during the extraction process.

💡 Pro Tip: Use Replay’s "Blueprints" to identify redundant business logic. Often, legacy systems have five different ways to perform the same calculation across different screens. Replay identifies these patterns, allowing you to consolidate them into a single, reusable React hook.

typescript
// Replay identified redundant logic across 4 ActiveX controls
// Consolidated into a single, documented React Hook
export function usePremiumCalculation() {
  const calculate = (baseRate: number, riskFactor: number) => {
    // Logic extracted from legacy 'PremiumCalc.dll'
    const adjustment = baseRate * (riskFactor / 100);
    return baseRate + adjustment;
  };

  return { calculate };
}

Security and Compliance in Regulated Environments#

For industries like Healthcare (HIPAA) and Government, moving away from ActiveX is a security mandate. However, the migration process itself must be secure. Replay is built for these environments:

• •SOC2 Type II Compliant
• •HIPAA-ready data masking: Sensitive PII/PHI is redacted during the recording and extraction process.
• •On-Premise Deployment: For air-gapped systems or highly sensitive data, Replay can run entirely within your firewall.

The Future Isn't Rewriting—It's Understanding#

The browser compatibility crisis isn't going away. As web standards evolve, today's "modern" React app will eventually become tomorrow's legacy. The companies that succeed won't be the ones who rewrite their entire stack every five years; they will be the ones who have a continuous pulse on their application logic.

Replay provides that pulse. By turning user workflows into documented, executable code, we transform legacy systems from "black boxes" into transparent, manageable assets.

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Frequently Asked Questions#

How does Replay handle ActiveX controls that don't run in a modern browser?#

Replay utilizes a secure, containerized environment that can run legacy IE/ActiveX sessions. We record the interactions within this controlled environment to extract the visual and data states, which are then used to generate the modern React equivalent.

Do we need the original source code (VB6/C++) for the ActiveX controls?#

No. Replay is a Visual Reverse Engineering platform. We observe the inputs, outputs, and UI behaviors. While having source code is helpful, Replay is designed to work when the source code is lost, undocumented, or unbuildable.

What is the average time savings?#

Our partners see an average of 70% time savings. A screen that takes a senior developer 40-50 hours to manually reverse-engineer, document, and rebuild in React typically takes about 4 hours using Replay’s automated extraction and Blueprint editor.

Can Replay generate tests for the new React components?#

Yes. Replay automatically generates E2E test suites (Playwright/Cypress) and Unit Tests (Jest/Vitest) based on the recorded legacy workflows. This ensures that the new component behaves exactly like the original.

Which frameworks does Replay support for the output?#

While we focus heavily on React and TypeScript, Replay can be configured to output components for Angular, Vue, and even plain HTML/CSS, depending on your enterprise standards.

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