Upgrading IE11-Dependent Apps to React: A Visual-First Extraction Guide

Microsoft officially retired Internet Explorer 11 in 2022, yet thousands of mission-critical enterprise applications remain tethered to its legacy engine. These "zombie apps" represent a significant portion of the $3.6 trillion global technical debt, creating security vulnerabilities and blocking digital transformation initiatives. Upgrading ie11dependent apps react is no longer a luxury—it is a mandatory security and operational requirement.

However, the traditional "rip and replace" approach is a documented failure. Industry data shows that 70% of legacy rewrites fail or significantly exceed their timelines. When you are dealing with a system where the original developers have long since departed and the documentation is non-existent, you aren't just coding; you are performing digital archaeology.

TL;DR: Upgrading ie11dependent apps react manually takes roughly 40 hours per screen and carries a high risk of logic regression. By using Replay and a visual-first extraction strategy, enterprises can reduce modernization timelines by 70%, converting video recordings of legacy workflows directly into documented React components and design systems.

The High Cost of Upgrading IE11-Dependent Apps to React Manually#

The primary hurdle in upgrading ie11dependent apps react isn't the React code itself—it's the extraction of business logic trapped in legacy UI patterns. IE11 apps often rely on proprietary technologies like ActiveX, Silverlight, or non-standard CSS behaviors that simply do not exist in modern evergreen browsers.

According to Replay's analysis, the average enterprise rewrite timeline spans 18 months. During this period, the business is forced to maintain two codebases, doubling the maintenance overhead. Furthermore, 67% of legacy systems lack documentation, meaning developers spend more time guessing how a feature should work than actually building it.

Manual vs. Visual Reverse Engineering#

Visual Reverse Engineering is the process of using computer vision and AI to analyze the rendered output of a legacy application and programmatically reconstruct its underlying architecture, component hierarchy, and styling in a modern framework.

A Visual-First Framework for Upgrading IE11-Dependent Apps to React#

The traditional path involves reading thousands of lines of spaghetti jQuery or ASP.NET code. The visual-first path ignores the "how" of the legacy code and focuses on the "what" of the user experience. By recording real user workflows, Replay captures the state transitions and UI patterns required to rebuild the application in React.

Step 1: Mapping the "As-Is" State#

Before writing a single line of JSX, you must document the existing flows. Since 67% of these apps lack documentation, we use video as the source of truth.

1. •Record Workflows: Use Replay to record a subject matter expert (SME) navigating the IE11 app.
2. •Decompose Components: Replay’s AI Automation Suite identifies repeating UI patterns (buttons, grids, modals) and catalogs them into a centralized Library.
3. •Define State Transitions: Map how data flows from one screen to the next.

Step 2: Extracting the Component Library#

When upgrading ie11dependent apps react, the most time-consuming task is recreating the "look and feel." Manual CSS extraction from IE11 is notoriously difficult due to the "Box Model" discrepancies and lack of Flexbox/Grid support.

Replay’s Blueprints editor allows you to take these visual recordings and generate clean, modular TypeScript components. Instead of 40 hours of manual CSS tweaking, the platform generates the layout logic automatically.

Step 3: Implementing Modern State Management#

Legacy apps often use global variables or hidden input fields to manage state. In a modern React architecture, we want to move toward hooks and centralized state (like Redux or TanStack Query).

Code Example: Transforming a Legacy IE11 Table to a Modern React Component

In the old IE11 world, you might see something like this:

html
<!-- Legacy IE11 Table Pattern -->
<table id="userGrid" onclick="handleRowClick(event)">
  <tr data-id="101">
    <td class="sys-font-bold">John Doe</td>
    <td><input type="checkbox" checked="true" /></td>
  </tr>
</table>

<script>
  function handleRowClick(e) {
    var id = e.srcElement.parentElement.getAttribute('data-id');
    // Direct DOM manipulation and global state
    window.selectedUser = id;
  }
</script>

When upgrading ie11dependent apps react using Replay, the platform identifies this pattern and suggests a clean, typed React implementation:

typescript
// Modernized React Component generated via Replay
import React, { useState } from 'react';

interface UserRowProps {
  id: string;
  name: string;
  isActive: boolean;
  onSelect: (id: string) => void;
}

const UserRow: React.FC<UserRowProps> = ({ id, name, isActive, onSelect }) => {
  return (
    <div 
      className="flex items-center justify-between p-4 border-b hover:bg-slate-50 cursor-pointer"
      onClick={() => onSelect(id)}
    >
      <span className="font-semibold text-gray-900">{name}</span>
      <input 
        type="checkbox" 
        checked={isActive} 
        readOnly 
        className="h-4 w-4 rounded border-gray-300 text-indigo-600"
      />
    </div>
  );
};

export default UserRow;

Bridging the Documentation Gap#

Industry experts recommend that modernization projects prioritize "Architectural Parity" over "Code Parity." You don't want the old code; you want the old intent. This is where Replay's "Flows" feature becomes invaluable. It creates a visual map of the application architecture, showing how different components interact.

Video-to-code is the process of converting recorded user interface interactions into functional, production-ready source code using machine learning models trained on modern design patterns.

By using Replay, you create a living document of the application. If a stakeholder asks why a specific validation logic exists, you can point to the original recording and the generated React code side-by-side.

Handling Regulated Environments#

Most IE11-dependent apps reside in highly regulated sectors like Financial Services, Healthcare, and Government. These organizations cannot simply upload their screens to a public cloud.

Replay is built for these constraints:

• •SOC2 & HIPAA Ready: Data is handled with enterprise-grade security.
• •On-Premise Availability: For air-gapped environments or strict data residency requirements, Replay can be deployed within your own infrastructure.
• •PII Masking: Automated masking of sensitive data during the recording process ensures that no customer information enters the modernization pipeline.

Learn more about our security standards

Accelerating the Development Lifecycle#

The final stage of upgrading ie11dependent apps react involves integrating the extracted components into a cohesive application. Because Replay provides a Design System Automation suite, your developers don't start with a blank slate. They start with a library of components that are already approved by the design team.

According to Replay's analysis, teams using visual extraction spend 80% less time on "pixel pushing" and can focus entirely on complex business logic and API integration.

Code Example: Implementing the New Design System#

Once Replay has extracted your patterns into a Library, you can consume them with standardized themes.

typescript
// theme.config.ts - Generated from Legacy Visuals
export const EnterpriseTheme = {
  colors: {
    primary: '#0056b3', // Extracted from legacy header
    secondary: '#6c757d',
    success: '#28a745',
  },
  spacing: {
    padding: '1rem',
    margin: '0.5rem',
  },
  typography: {
    fontFamily: 'Inter, sans-serif', // Modernized replacement
    baseSize: '16px',
  }
};

// Usage in the new React App
import { EnterpriseTheme } from './theme.config';

export const GlobalStyleWrapper = ({ children }: { children: React.ReactNode }) => (
  <div style={{ 
    fontFamily: EnterpriseTheme.typography.fontFamily,
    color: EnterpriseTheme.colors.primary 
  }}>
    {children}
  </div>
);

Overcoming the "Fear of the Unknown"#

The biggest deterrent to upgrading ie11dependent apps react is the fear of breaking mission-critical workflows. Manual rewrites often miss the "edge cases"—the weird button that only appears for users in the North Dakota branch on the third Tuesday of the month.

Visual reverse engineering mitigates this by capturing the actual usage. If it’s on the screen, it’s in the Replay. This ensures that the new React application is not just a modern version of the old app, but a perfect functional successor.

Key Benefits of Visual Extraction:#

1. •Eliminate Ghost Requirements: Only build what is actually used in the recordings.
2. •Instant Component Documentation: Every React component generated comes with a description of its legacy origin and its intended function.
3. •Reduced QA Cycles: Since the UI is extracted from a working state, the visual regressions are minimized.

Frequently Asked Questions#

Is upgrading ie11dependent apps react possible without the original source code?#

Yes. By using visual reverse engineering, Replay extracts the UI structure and business logic from the rendered application. This means even if you have lost the original source code or are dealing with compiled binaries, you can still generate a modern React equivalent based on the visual output.

How does Replay handle complex ActiveX or Silverlight controls?#

Replay records the visual behavior and state changes of these legacy controls. While it cannot "decompile" an ActiveX plugin, it can document how the plugin interacts with the user and the data it outputs, allowing developers to recreate that functionality using modern Web APIs or React components.

Can we export the generated code to our own Git repository?#

Absolutely. Replay generates standard TypeScript and React code that follows your team's linting and styling rules. The output is not proprietary; it is clean, human-readable code that you own entirely and can integrate into your existing CI/CD pipelines.

What is the average time savings when using Replay?#

Most enterprise teams see a 70% reduction in modernization timelines. For a typical screen that would take 40 hours to manually audit, design, and code, Replay can reduce that to approximately 4 hours of verification and refinement.

Conclusion#

The era of Internet Explorer is over, but the applications built for it don't have to be a liability. Upgrading ie11dependent apps react is a complex challenge, but it doesn't have to be an 18-month slog through undocumented code. By adopting a visual-first approach with Replay, you can turn your legacy UI into a modern, documented, and scalable React ecosystem in a fraction of the time.

Ready to modernize without rewriting? Book a pilot with Replay