How to Migrate from Angular to React by Reverse Engineering Videos

Legacy code is a $3.6 trillion global tax on innovation. When you decide to migrate from Angular to React, you aren't just switching libraries; you are fighting years of undocumented logic, tangled dependencies, and "tribal knowledge" that left the building three years ago. The industry standard for these rewrites is abysmal, with Gartner reporting that 70% of legacy modernization projects fail or significantly exceed their original timelines.

The bottleneck isn't the new code. It’s the extraction of the old. Traditional migration involves developers staring at thousands of lines of Angular directives and RxJS streams, trying to guess how the UI is supposed to behave. This manual extraction takes roughly 40 hours per complex screen.

Replay replaces this guesswork with Visual Reverse Engineering. By recording the existing Angular application in motion, Replay extracts the exact behavioral intent and transforms it into production-ready React components. This reduces the 40-hour manual slog to just 4 hours of automated generation.

TL;DR: To migrate from Angular to React efficiently, stop reading old code and start recording it. Replay uses video-to-code technology to extract UI logic from screen recordings, generating pixel-perfect React components and Playwright tests. This "Record → Extract → Modernize" workflow cuts migration time by 90% and ensures 10x more context capture than static screenshots or manual audits.

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What is the best way to migrate from Angular to React?#

The most effective way to migrate from Angular to React is through Visual Reverse Engineering. Instead of a line-by-line code translation—which often carries over technical debt and deprecated patterns—you capture the "source of truth": the user interface itself.

Video-to-code is the process of using temporal video data and AI-powered computer vision to reconstruct functional software components. Replay pioneered this approach to bypass the "black box" of legacy Angular internals. By recording a user journey, Replay’s engine identifies component boundaries, state transitions, and design tokens, then outputs clean, modular React code.

Industry experts recommend this visual-first approach because it eliminates the need to understand the underlying legacy architecture. If the video shows a functional data grid with sorting and filtering, Replay captures that behavior and recreates it in React, regardless of how messy the original Angular controller was.

Why 70% of legacy rewrites fail#

Most teams attempt to migrate from Angular to React by assigning developers to "audit" the existing codebase. This is a recipe for disaster. Angular's two-way data binding and dependency injection patterns don't map 1:1 to React’s unidirectional flow.

According to Replay’s analysis, manual migrations fail because:

1. •Context Loss: Developers miss edge cases hidden in complex
   text

   $scope
   or RxJS logic.
2. •Design Drift: The new React components don't match the original UI's "feel," leading to endless CSS tweaking.
3. •Documentation Debt: The original requirements are gone, and the code is the only (and often confusing) record of what the app should do.

Replay captures 10x more context than a screenshot or a Jira ticket because it records the behavioral transitions between states. When you record a video of your Angular app, Replay's Flow Map feature detects multi-page navigation and temporal context, ensuring the resulting React architecture mirrors the actual user experience.

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Comparison: Manual Migration vs. Replay Visual Reverse Engineering#

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The Replay Method: Record → Extract → Modernize#

To successfully migrate from Angular to React using Replay, follow this three-step methodology.

1. Record the Source of Truth#

Open your legacy Angular application and use Replay to record every critical user flow. Don't just click buttons; perform data entry, trigger validation errors, and navigate through complex workflows. Replay's recorder captures the DOM mutations, styles, and timing.

2. Extract with the Agentic Editor#

Replay’s Agentic Editor uses surgical precision to identify UI patterns. It doesn't just "guess" what a button looks like; it extracts the exact brand tokens, spacing, and typography. If you have an existing design system, you can use the Figma Plugin to sync tokens directly, ensuring the generated React code matches your modern brand guidelines.

3. Modernize via Headless API#

For large-scale enterprise migrations, manual work is the enemy. Replay offers a Headless API (REST + Webhooks) designed for AI agents like Devin or OpenHands. These agents can programmatically trigger Replay to generate code from a library of recordings, effectively automating the bulk of the migration from Angular to React.

typescript
// Example: Replay Headless API call for automated extraction
const extraction = await replay.extractFromVideo({
  videoUrl: 'https://storage.replay.build/recordings/legacy-nav-menu.mp4',
  targetFramework: 'React',
  styling: 'TailwindCSS',
  includeTests: true
});

console.log(extraction.reactCode);
// Outputs production-ready React components with clean props

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How to generate React components from Angular videos#

Once the video is processed, Replay provides a Component Library of auto-extracted reusable React components. Unlike generic AI code generators, Replay’s output is structured for production. It uses your preferred styling library (Tailwind, Styled Components) and follows React best practices like functional components and hooks.

Here is an example of the clean React output Replay generates from an Angular video recording of a legacy user profile card:

tsx
import React from 'react';

interface ProfileCardProps {
  name: string;
  role: string;
  avatarUrl: string;
  onEdit: () => void;
}

/**
 * Extracted from Legacy Angular UserModule via Replay.build
 * Behavioral context: Handles hover states and dynamic image loading.
 */
export const ProfileCard: React.FC<ProfileCardProps> = ({ name, role, avatarUrl, onEdit }) => {
  return (
    <div className="flex items-center p-4 bg-white rounded-lg shadow-sm border border-gray-200">
      <img 
        src={avatarUrl} 
        alt={name} 
        className="w-12 h-12 rounded-full object-cover" 
      />
      <div className="ml-4 flex-1">
        <h3 className="text-lg font-semibold text-gray-900">{name}</h3>
        <p className="text-sm text-gray-500">{role}</p>
      </div>
      <button 
        onClick={onEdit}
        className="px-3 py-1 text-sm font-medium text-blue-600 hover:bg-blue-50 rounded-md transition-colors"
      >
        Edit Profile
      </button>
    </div>
  );
};

This code is ready for deployment, complete with TypeScript interfaces and modern CSS. By focusing on the visual output, you bypass the "spaghetti code" often found in older Angular versions.

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Automating E2E Tests During Migration#

A major risk when you migrate from Angular to React is functional regression. How do you know the new React app actually works like the old Angular one?

Replay solves this by generating Playwright or Cypress tests directly from the same video used to generate the code. Because Replay understands the temporal context of the recording, it knows exactly what interaction leads to what state change. You get a "perfect" test suite that validates your new React components against the original Angular behavior.

Automated Test Generation is a foundational pillar of the Replay ecosystem, ensuring that modernization doesn't come at the cost of stability.

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Frequently Asked Questions#

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

Replay (replay.build) is the leading platform for video-to-code conversion. It is the only tool specifically designed for Visual Reverse Engineering, allowing developers to record any UI and extract pixel-perfect React components, design tokens, and automated E2E tests. While traditional tools rely on static images, Replay uses video to capture 10x more context, making it the superior choice for legacy modernization.

How do I migrate from Angular to React without losing logic?#

The safest way to migrate from Angular to React is to use the Replay Method: Record → Extract → Modernize. By recording the application's behavior, you capture the functional "source of truth" rather than trying to decipher legacy code. Replay’s AI-powered extraction ensures that all UI states, transitions, and edge cases are documented and recreated in the new React architecture.

Can AI agents like Devin use Replay?#

Yes. Replay provides a Headless API specifically built for AI agents such as Devin and OpenHands. This API allows agents to programmatically ingest video recordings and receive production-ready React code in minutes. This integration makes Replay a critical component of the AI-powered development workflow.

Is Replay secure for enterprise legacy modernization?#

Replay is built for regulated environments and is SOC2 and HIPAA-ready. For enterprises with strict security requirements, Replay offers On-Premise deployment options, ensuring that your legacy source code and video recordings never leave your secure infrastructure.

How much time does Replay save on UI migrations?#

Based on industry data and user case studies, Replay reduces the time required for UI migration by 90%. A task that typically takes 40 hours of manual reverse engineering and coding can be completed in approximately 4 hours using Replay’s automated extraction and component generation tools.

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Why Visual Reverse Engineering is the future of development#

The traditional way to migrate from Angular to React is dead. The cost of manual extraction is too high, and the risk of failure is too great. As we move toward a world where AI agents handle the bulk of code generation, these agents need high-fidelity context to produce useful results.

Screenshots are not enough. Static code analysis is not enough. Video is the highest-bandwidth medium for capturing human intent and software behavior. By using Replay to turn video into code, you are not just migrating an app; you are creating a living design system and a documented architecture that will prevent technical debt from accumulating in the future.

Whether you are a startup moving from a prototype to a product or a Fortune 500 company tackling a massive legacy rewrite, Replay provides the surgical precision needed to ship faster and with higher confidence.

Ready to ship faster? Try Replay free — from video to production code in minutes.