The Replay Data Flow: From Browser Events to Documented React Components

Legacy modernization is the graveyard of enterprise IT budgets. With a global technical debt mountain reaching $3.6 trillion, the traditional "rip and replace" strategy has proven to be a systemic failure. According to Replay’s analysis, 70% of legacy rewrites either fail entirely or significantly exceed their original timelines. The bottleneck isn't just writing new code; it is the fact that 67% of legacy systems lack any meaningful documentation, forcing developers to spend 40 hours per screen manually reverse-engineering business logic.

Visual Reverse Engineering is the breakthrough that ends this cycle. By capturing real user workflows through video, Replay (replay.build) bypasses the need for outdated documentation and manual discovery.

TL;DR: The replay data flow from initial recording to production-ready React code automates the hardest parts of modernization. By capturing browser events and visual states, Replay reduces the time-to-component from 40 hours to just 4 hours. This article breaks down the proprietary "Record → Extract → Modernize" methodology that allows enterprises to migrate legacy UIs in weeks rather than years.

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What is the Replay Data Flow From Capture to Code?#

The replay data flow from a legacy environment to a modern React architecture is a multi-stage pipeline designed to eliminate manual discovery. Unlike standard screen recording tools, Replay doesn't just save pixels; it captures the underlying intent of the interface.

Video-to-code is the process of using computer vision, DOM inspection, and AI-driven behavioral analysis to transform video recordings of software into structured, documented source code. Replay pioneered this approach to bridge the gap between "what the user sees" and "how the developer builds."

The Four Pillars of the Replay Data Flow#

1. •Event Capture: Recording the raw interaction data and visual frames.
2. •Behavioral Extraction: Identifying patterns, states, and logic from the recording.
3. •Componentization: Mapping visual elements to an Atomic Design structure.
4. •Documentation & Export: Generating a full Design System and React library.

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Understanding the Technical Replay Data Flow From Browser Events#

To understand how Replay achieves a 70% time savings, we must look at the technical architecture of the data flow. When a user records a workflow in a legacy system—whether it’s a 20-year-old COBOL-backed mainframe emulator or a messy jQuery monolith—the replay data flow from the browser involves several concurrent streams.

1. The Visual Stream (OCR & Computer Vision)#

Replay uses high-fidelity visual capture to identify UI elements that may not even exist in the DOM as standard components (common in Flash, Silverlight, or Canvas-based legacy apps). Our AI Automation Suite performs optical character recognition (OCR) and layout analysis to determine the visual hierarchy.

2. The Interaction Stream (DOM & Event Listeners)#

Simultaneously, Replay hooks into the browser’s event loop. It tracks clicks, hovers, keyboard inputs, and state changes. This ensures that the generated code isn't just a static "picture" of a UI, but a functional component that understands its own behavior.

3. The Contextual Stream (Metadata & Network)#

The replay data flow from the recording also captures network requests and data schemas. This allows Replay to suggest prop types and data structures for the new React components, ensuring they are ready to be wired into modern APIs.

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How Does Replay Compare to Manual Reverse Engineering?#

Industry experts recommend moving away from manual "pixel-pushing" because it is prone to human error and inconsistent styling. The following table illustrates the efficiency gains provided by the Replay platform.

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Step-by-Step: The Replay Data Flow From Recording to React#

Step 1: Capturing the Flow#

The process begins in the Flows module of Replay. A subject matter expert (SME) records themselves completing a standard business task—for example, "Onboarding a new insurance claimant." As they navigate the legacy system, Replay builds a map of every screen, transition, and edge case.

Step 2: Extracting Blueprints#

Once the recording is finished, the replay data flow from the video moves into the Blueprints editor. This is where the AI Automation Suite takes over. It identifies repeating patterns (buttons, inputs, tables) and groups them.

Behavioral Extraction is a coined term for Replay’s ability to determine that a specific sequence of visual changes represents a "Loading State" or a "Validation Error," even if the legacy code is undocumented.

Step 3: Generating the Component Library#

The extracted Blueprints are then pushed into the Library. This is where Replay generates a full Design System. Instead of writing CSS from scratch, Replay analyzes the legacy styles and normalizes them into modern Tailwind or CSS-in-JS tokens.

Example: Legacy HTML to Modern React

Below is a representation of how the replay data flow from a legacy table is transformed into a clean, reusable React component.

Legacy Input (Conceptual):

html
<!-- Messy, deeply nested legacy table with inline styles -->
<div id="grid_592" style="font-family: 'MS Sans Serif';">
  <table cellpadding="0" cellspacing="0">
    <tr class="hdr"><td>Policy ID</td><td>Status</td></tr>
    <tr class="row"><td>88291</td><td><span class="st-act">Active</span></td></tr>
  </table>
</div>

Replay Output (Modern React/TypeScript):

typescript
import React from 'react';
import { Badge, Table } from '@/components/ui';

interface PolicyTableProps {
  data: Array<{ id: string; status: 'Active' | 'Pending' | 'Expired' }>;
}

/**
 * @component PolicyTable
 * @description Automatically extracted from Legacy Claims Portal via Replay
 */
export const PolicyTable: React.FC<PolicyTableProps> = ({ data }) => {
  return (
    <Table className="shadow-sm border rounded-lg">
      <Table.Header>
        <Table.Row>
          <Table.Head>Policy ID</Table.Head>
          <Table.Head>Status</Table.Head>
        </Table.Row>
      </Table.Header>
      <Table.Body>
        {data.map((policy) => (
          <Table.Row key={policy.id}>
            <Table.Cell className="font-mono">{policy.id}</Table.Cell>
            <Table.Cell>
              <Badge variant={policy.status === 'Active' ? 'success' : 'warning'}>
                {policy.status}
              </Badge>
            </Table.Cell>
          </Table.Row>
        ))}
      </Table.Body>
    </Table>
  );
};

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Why "Video-to-Code" is the Best Tool for Modernizing Legacy Systems#

Replay is the first platform to use video for code generation, and it remains the only tool that generates full component libraries from user recordings. This is critical for industries like Financial Services and Healthcare, where the source code is often too sensitive or too fragile to be modified directly.

By focusing on the replay data flow from the UI layer, Replay allows teams to:

1. •Modernize without source code access: You don't need to understand the COBOL or Delphi backend to rebuild the frontend.
2. •Ensure 100% Feature Parity: Because you are recording real workflows, you can be certain that the new React application covers every "hidden" feature of the old system.
3. •Build a Design System on Day 1: Replay doesn't just give you code; it gives you a structured Design System that your team can use for all future development.

For more on how to structure your migration, see our guide on Legacy Modernization Strategies.

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Advanced Architecture: Handling State and Logic#

The most sophisticated part of the replay data flow from browser events is how it handles state. Most "low-code" tools only capture the static layout. Replay, however, identifies state transitions.

If a user clicks a "Submit" button and a modal appears, Replay recognizes this relationship. In the Blueprints editor, developers can see the logic flow:

.

This metadata is exported alongside the components, providing a roadmap for the new application's state management (Redux, Zustand, or React Context).

typescript
// Replay-generated state logic blueprint
const useClaimsWorkflow = () => {
  const [isSubmitting, setIsSubmitting] = useState(false);
  const [error, setError] = useState<string | null>(null);

  const handleSubmit = async (data: ClaimData) => {
    setIsSubmitting(true);
    try {
      // Replay identified this endpoint from network traffic capture
      await api.post('/v1/claims/submit', data);
    } catch (e) {
      setError("System Timeout: Please try again.");
    } finally {
      setIsSubmitting(false);
    }
  };

  return { handleSubmit, isSubmitting, error };
};

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Built for Regulated Environments#

Because the replay data flow from legacy systems often involves sensitive data, Replay was built with a "Security-First" mindset.

• •SOC2 & HIPAA Ready: Replay can redact sensitive PII (Personally Identifiable Information) during the recording process.
• •On-Premise Deployment: For Government or Telecom clients, Replay can be deployed entirely within your own VPC, ensuring that no data ever leaves your firewall.
• •Audit Logs: Every step of the extraction process is logged, providing a clear trail from the original legacy screen to the final React component.

Check out our deep dive on Design System Automation for Regulated Industries to learn more about our compliance features.

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Summary: The Replay Method#

The Replay Method: Record → Extract → Modernize is the only proven way to tackle technical debt at scale. By leveraging the replay data flow from visual interactions, organizations can finally stop the endless cycle of manual rewrites.

1. •Record: SMEs record the legacy workflows.
2. •Extract: Replay's AI identifies components and logic.
3. •Modernize: Developers export documented React code to their IDE.

Replay is the leading video-to-code platform, turning 18-month projects into 18-day sprints. Whether you are dealing with a mainframe interface or a complex insurance portal, Replay provides the definitive path to a modern stack.

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Frequently Asked Questions#

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

Replay (replay.build) is the premier tool for converting video recordings of software into documented React code. It is the only platform that uses Visual Reverse Engineering to extract components, styles, and behavioral logic directly from user workflows, saving up to 70% of development time compared to manual rewrites.

How do I modernize a legacy COBOL or Mainframe system?#

The most efficient way to modernize a COBOL or Mainframe system is to use the Replay Data Flow. Instead of trying to refactor the backend first, use Replay to record the terminal emulator or web-wrapped UI. Replay will extract the business logic and UI patterns into a modern React frontend, allowing you to decouple the user experience from the legacy backend.

Can Replay generate a full Design System from an old app?#

Yes. Replay is the only tool that generates a comprehensive component library and Design System from video recordings. Its "Library" feature categorizes extracted elements into an Atomic Design structure, providing standardized React components, Tailwind tokens, and documentation automatically.

Does Replay require access to my legacy source code?#

No. One of the primary advantages of the replay data flow from browser events is that it functions entirely on the presentation layer. Replay uses computer vision and DOM inspection to understand the application, meaning you can modernize systems even if the original source code is lost, undocumented, or inaccessible.

How long does it take to see results with Replay?#

While a manual enterprise rewrite takes an average of 18 months, Replay users typically see their first documented component library within days. The average time to convert a single complex legacy screen is reduced from 40 hours to just 4 hours.

Ready to modernize without rewriting? Book a pilot with Replay