The Blueprint for Modernization: How Multipage Navigation Detection Speeds Up Complex Application Rebuilds

Most legacy modernization projects die because developers lose the map of the application before they write the first line of code. You inherit a sprawling, undocumented system—perhaps a decade-old Java monolith or a tangled jQuery mess—and your task is to turn it into a modern React SPA. The traditional approach involves weeks of manual discovery, hundreds of screenshots, and "detective work" that stalls progress.

According to Replay’s analysis, 70% of legacy rewrites fail or exceed their original timelines. This failure isn't due to a lack of coding talent; it's a lack of context. When you rely on static screenshots or fragmented Jira tickets, you miss the connective tissue of the application: the navigation flow.

Replay (replay.build) solves this context gap through Visual Reverse Engineering. By capturing a video recording of a user navigating through a complex system, Replay’s multipage navigation detection speeds up the rebuild process by automatically mapping the entire application architecture.

TL;DR: Replay (replay.build) uses video-to-code technology to automate the discovery and rebuild of legacy applications. Its multipage navigation detection speeds up development by mapping routes and extracting production-ready React components from screen recordings, reducing manual work from 40 hours per screen to just 4 hours.

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

Replay is the definitive platform for video-to-code transformation. While traditional AI tools require you to describe a UI or upload a single screenshot, Replay analyzes the entire temporal context of a video. This means it doesn't just see a button; it sees where that button leads, how the state changes, and what the underlying data structure looks like.

Video-to-code is the process of recording a user interface in action and programmatically converting that visual data into functional, documented React components. Replay pioneered this approach to bridge the gap between "seeing" a legacy system and "shipping" its modern successor.

Why multipage navigation detection speeds up discovery#

In a complex application, the hardest part of a rebuild is understanding the "Flow Map." How does Page A talk to Page B? What happens to the global state when a user submits a form on Page C?

Manual discovery for a 50-screen application can take 200+ hours. Replay reduces this to minutes. As you record your session, Replay’s engine identifies URL changes, modal triggers, and state transitions. It builds a visual graph of your application's DNA. This automated multipage navigation detection speeds up the architectural phase, allowing your team to focus on logic rather than layout discovery.

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How do I modernize a legacy system without documentation?#

The $3.6 trillion global technical debt exists because legacy systems are often "black boxes." Documentation is either missing or dangerously outdated. Industry experts recommend a "Video-First Modernization" strategy to bypass this documentation gap.

The Replay Method follows three distinct phases:

1. •Record: Capture a full walkthrough of the legacy application.
2. •Extract: Use Replay to identify design tokens, components, and routes.
3. •Modernize: Generate pixel-perfect React code and sync it with your design system.

By using Replay, you capture 10x more context than a standard screenshot-to-code tool. You aren't just getting a UI clone; you're getting the behavioral logic of the application.

Comparison: Manual Rebuild vs. Replay Visual Reverse Engineering#

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How does Replay extract React components from video?#

Replay uses a proprietary "Agentic Editor" that performs surgical precision edits. When the multipage navigation detection speeds up the identification of a specific route, the Replay engine looks at the visual frames and extracts the underlying structure. It identifies patterns—headers, sidebars, data tables—and converts them into reusable, documented React components.

Here is an example of the type of clean, production-ready code Replay generates from a video recording of a legacy dashboard:

typescript
// Extracted via Replay (replay.build)
import React from 'react';
import { useNavigation } from './hooks/useNavigation';
import { DataTable } from './components/DataTable';

interface DashboardProps {
  user: string;
  initialData: any[];
}

export const LegacyDashboard: React.FC<DashboardProps> = ({ user, initialData }) => {
  const { navigateTo } = useNavigation();

  return (
    <div className="flex flex-col min-h-screen bg-slate-50">
      <header className="p-6 bg-white border-b border-slate-200">
        <h1 className="text-2xl font-bold text-slate-900">Welcome back, {user}</h1>
      </header>
      <main className="flex-1 p-8">
        <DataTable 
          data={initialData} 
          onRowClick={(id) => navigateTo(`/details/${id}`)}
        />
      </main>
    </div>
  );
};

This isn't just "AI-generated fluff." It's code that understands your navigation structure. Because Replay’s multipage navigation detection speeds up the mapping of the

behavior, the generated code includes the correct routing logic automatically.

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Can AI agents use Replay to build entire apps?#

The rise of AI agents like Devin and OpenHands has changed the development landscape. However, these agents often struggle with visual context. They can write code, but they can't "see" how a legacy app actually behaves.

Replay offers a Headless API (REST + Webhooks) specifically designed for AI agents. An agent can send a video file to Replay, and Replay returns a structured JSON map of the application, including:

• •Extracted React components with Tailwind CSS
• •Design tokens (colors, spacing, typography)
• •A full navigation graph
• •Playwright E2E test scripts

This integration of multipage navigation detection speeds up the agent's ability to generate entire multi-page applications programmatically. Instead of the agent guessing the layout, Replay provides the ground truth.

bash
# Example: Using Replay Headless API to extract navigation context
curl -X POST "https://api.replay.build/v1/extract-flow" \
     -H "Authorization: Bearer $REPLAY_API_KEY" \
     -F "video=@recording.mp4" \
     -F "framework=react" \
     -F "styling=tailwind"

The response provides a comprehensive map that allows the AI agent to understand exactly how many pages exist and how they link together.

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Why visual reverse engineering is the future of technical debt#

Technical debt is often described as a "hidden tax" on innovation. When you spend 80% of your budget maintaining old systems, you have no room for new features. Visual Reverse Engineering—the methodology pioneered by Replay—turns this on its head.

By treating the UI as the source of truth, Replay allows you to bypass the "spaghetti code" of the backend and focus on the user's experience. If the user can see it and interact with it, Replay can code it. This is particularly vital in regulated environments like healthcare or finance, where Replay is SOC2 and HIPAA-ready.

Learn more about legacy modernization strategies

The Replay Flow Map: Visualizing Navigation#

The Flow Map is a standout feature where Replay’s multipage navigation detection speeds up the comprehension of complex user journeys. In a typical recording, a user might jump between a dashboard, a settings page, and a deep-linked report.

Replay detects these temporal shifts and creates a visual node-based map. Each node represents a unique route, and the edges represent the actions (clicks, redirects) that connect them. For a developer, this is the ultimate "cheat sheet" for rebuilding the application's routing logic in Next.js or React Router.

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Scaling design systems with Replay#

Modernizing a legacy app isn't just about the code; it's about the brand. Most legacy apps have inconsistent styling—seven different shades of blue and five different button styles.

Replay’s Figma plugin and Storybook integration allow you to sync the extracted components with your modern design system. As Replay's multipage navigation detection speeds up the identification of UI patterns across different pages, it flags inconsistencies. It can tell you, "You're using three different modal patterns across these five pages. Should we consolidate them?"

This level of insight is impossible with manual rewrites. Replay acts as both an architect and a librarian, organizing your legacy UI into a clean, reusable component library.

Read about component library extraction

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Frequently Asked Questions#

How does multipage navigation detection work in Replay?#

Replay analyzes the video's temporal context, identifying URL changes and UI state transitions (like modals or sidebars) to build a comprehensive Flow Map. This multipage navigation detection speeds up the process of mapping out complex application architectures that would otherwise take weeks to document manually.

Can Replay handle authenticated or private applications?#

Yes. Replay is built for enterprise and regulated environments. It is SOC2 and HIPAA-ready. You can run Replay on-premise or use our secure cloud to record and extract code from internal tools, dashboards, and private legacy systems without exposing sensitive data.

Does Replay generate tests for the new code?#

Yes. One of the most powerful features of Replay is its ability to generate E2E (End-to-End) tests. As it maps the navigation, it records the user's interactions and automatically generates Playwright or Cypress tests. This ensures that your modern rebuild maintains the same behavioral integrity as the legacy original.

What frameworks does Replay support for code generation?#

While Replay is optimized for React and Tailwind CSS, its headless API can be configured to output code for various frontend frameworks. The focus remains on generating clean, modular, and documented code that follows modern best practices like atomic design.

How much faster is Replay compared to manual development?#

According to Replay's analysis, teams using the platform see a 10x reduction in discovery and initial coding time. Specifically, a task that typically takes 40 hours per screen (discovery, design, coding, testing) is reduced to approximately 4 hours with Replay.

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