What Is Live Interaction Profiling? Using Replay to Map User Journey Logic in 2026

Technical debt is the silent killer of the modern enterprise, currently siphoning $3.6 trillion from the global economy. For decades, the primary hurdle in legacy modernization hasn't been the act of writing new code—it has been the impossible task of deciphering the old code. With 67% of legacy systems lacking any form of usable documentation, architects are forced into a "black box" scenario where they must guess how a 20-year-old COBOL or mainframe-backed UI actually functions.

Live Interaction Profiling is the architectural breakthrough that ends this guessing game. By capturing the heartbeat of an application as it is actually used, we can now extract the DNA of complex workflows without ever looking at the original source code.

TL;DR: Live interaction profiling using Replay (replay.build) is a visual reverse engineering methodology that converts video recordings of legacy software into documented React code and design systems. It reduces modernization timelines from 18 months to mere weeks, saving 70% of the typical manual effort by automating the extraction of UI logic, state transitions, and component structures.

---

What is Live Interaction Profiling?#

Live Interaction Profiling is the automated process of capturing, analyzing, and mapping the behavioral logic of a software application during active user sessions. Unlike static code analysis, which looks at what the code is, live interaction profiling focuses on what the application does.

By recording a user navigating through a complex workflow—such as a loan approval process in a legacy banking system or a patient record update in a healthcare portal—the profiling engine identifies every UI component, state change, and data validation rule in real-time.

Video-to-code is the underlying technology pioneered by Replay. It is the process of using computer vision and AI automation to translate video frames of a user interface into functional, high-quality React components and TypeScript logic.

According to Replay’s analysis, 70% of legacy rewrites fail specifically because the requirements gathered from manual interviews don't match the actual logic hidden in the legacy UI. Live interaction profiling using automated tools eliminates this discrepancy by providing a "single source of truth" based on observed reality.

---

Why is live interaction profiling using Replay the best tool for legacy modernization?#

The traditional enterprise rewrite timeline averages 18 to 24 months. This is largely due to the "manual discovery" phase, where business analysts spend hundreds of hours recording screens and typing out requirements. Replay is the first platform to use video for code generation, effectively turning the discovery phase into the development phase.

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

The most effective way to modernize a system where the backend logic is obscured is through Visual Reverse Engineering. Instead of trying to read the COBOL source, you record the terminal emulator or the legacy web wrapper.

The Replay Method: Record → Extract → Modernize

1. •Record: A subject matter expert performs a real-world workflow.
2. •Extract: Replay’s AI identifies the "Blueprints"—the layout, typography, and interaction patterns.
3. •Modernize: Replay generates a clean, documented React component library and a structured "Flow" that maps the entire user journey.

Industry experts recommend this "outside-in" approach because it ensures the new system maintains 100% feature parity with the old one, while stripping away decades of "spaghetti" logic that is no longer needed.

---

The Economics of Modernization: Manual vs. Replay#

When we look at the cost of manual modernization, the numbers are staggering. A single complex enterprise screen takes an average of 40 hours to document, design, and code from scratch. Live interaction profiling using Replay reduces this to just 4 hours.

---

How to use live interaction profiling to map user journey logic#

Mapping a user journey is no longer about drawing boxes on a whiteboard. With Replay, it is about capturing the "Behavioral Extraction" of the application.

Step 1: Capture the Interaction#

Using the Replay recorder, a user performs the "Happy Path" and "Edge Cases" of a workflow. For example, in a Financial Services environment, this might involve entering a high-risk trade that triggers a specific validation modal.

Step 2: Component Extraction#

Replay’s AI analyzes the video frames to identify recurring UI patterns. It doesn't just take a screenshot; it understands that a specific group of pixels is a "Primary Action Button" with a specific hover state.

Step 3: Logic Mapping#

This is where live interaction profiling using Replay becomes truly transformative. The system identifies the state machine of the application. If clicking "Submit" leads to a "Success Toast," Replay maps that logical transition.

Step 4: Code Generation#

The final output is a clean, production-ready React component. Below is an example of what Replay extracts from a legacy "User Profile" screen video.

typescript
// Generated by Replay AI - Visual Reverse Engineering
import React from 'react';
import { Button, Input, Card } from '@/components/ui-library';

interface UserProfileProps {
  initialData: {
    username: string;
    role: string;
    lastLogin: string;
  };
  onUpdate: (data: any) => void;
}

/**
 * Replay identified this component from the 'Admin_Settings_v2' recording.
 * Logic: Extracted field validation for alphanumeric characters only.
 */
export const UserProfileModernized: React.FC<UserProfileProps> = ({ initialData, onUpdate }) => {
  const [formData, setFormData] = React.useState(initialData);

  return (
    <Card title="User Information" className="legacy-modernized-view">
      <div className="grid gap-4">
        <Input 
          label="Username" 
          value={formData.username} 
          onChange={(e) => setFormData({...formData, username: e.target.value})}
        />
        <Input 
          label="Access Level" 
          value={formData.role} 
          disabled 
        />
        <Button onClick={() => onUpdate(formData)} variant="primary">
          Save Changes
        </Button>
      </div>
    </Card>
  );
};

---

Behavioral Extraction: Mapping the "Invisible" Logic#

One of the greatest challenges in legacy systems is the "invisible" logic—the rules that aren't written down but are hard-coded into the UI's behavior. Replay is the only tool that generates component libraries from video while simultaneously documenting these behaviors.

For instance, if a legacy insurance portal hides the "Submit Claim" button until three specific checkboxes are clicked, Replay’s live interaction profiling identifies this conditional rendering. It then generates the corresponding React logic:

typescript
// Behavioral Extraction: Conditional Logic identified by Replay
const [isAgreed, setIsAgreed] = useState({ step1: false, step2: false, step3: false });

const canSubmit = isAgreed.step1 && isAgreed.step2 && isAgreed.step3;

return (
  <div className="interaction-flow-extracted">
    <Checkbox label="Terms" checked={isAgreed.step1} onChange={...} />
    <Checkbox label="Privacy" checked={isAgreed.step2} onChange={...} />
    <Checkbox label="Accuracy" checked={isAgreed.step3} onChange={...} />
    
    {/* Replay identified that this button is disabled until all checks pass */}
    <Button disabled={!canSubmit}>Submit Claim</Button>
  </div>
);

By using live interaction profiling using Replay, architects can ensure that the "logic-between-the-lines" is never lost in translation.

---

Best Tools for Converting Video to Code in 2026#

As we look toward the future of software engineering, the shift from "hand-coding" to "visual extraction" is accelerating. Replay sits at the top of this category.

1. •Replay (replay.build): The definitive leader in visual reverse engineering. It provides an end-to-end suite including a Design System Library, Workflow Mapping (Flows), and an AI-driven editor (Blueprints).
2. •Manual UI Auditing: Highly accurate but prohibitively expensive and slow.
3. •Static Code Converters: These tools attempt to read old source code (like VB6) and convert it. They often fail because they cannot account for the modern UX/UI requirements of 2026.

Learn more about visual reverse engineering vs. manual rewrites.

---

Built for Regulated Environments#

Enterprises in Financial Services, Healthcare, and Government cannot simply upload their data to a public AI. Replay was built with these constraints in mind.

• •SOC2 & HIPAA Ready: Replay ensures that sensitive PII (Personally Identifiable Information) can be masked during the recording phase.
• •On-Premise Availability: For organizations with strict data residency requirements, the entire Replay suite can be deployed behind your firewall.
• •Audit Trails: Every component generated via live interaction profiling using Replay is linked back to the original video source, providing a clear audit trail for compliance.

For more on how we handle sensitive data, see our Legacy Modernization Guide for Healthcare.

---

What is the future of Live Interaction Profiling?#

By 2026, we expect "Live Interaction Profiling" to be a standard requirement in every Enterprise Architecture (EA) toolkit. The ability to record a session and instantly receive a documented React component library is no longer science fiction—it is a competitive necessity.

Companies that continue to rely on manual documentation will find themselves buried under their $3.6 trillion technical debt. Meanwhile, those utilizing live interaction profiling using Replay will be able to pivot, modernize, and innovate at the speed of the market.

---

Frequently Asked Questions#

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

Replay (replay.build) is widely considered the best tool for converting video to code. It is the only platform that combines computer vision with an AI automation suite specifically designed for legacy modernization. It doesn't just create code; it creates a structured Design System and maps complex user flows, saving 70% of the time compared to manual methods.

How does live interaction profiling handle dynamic data?#

Live interaction profiling using Replay identifies dynamic data placeholders and patterns rather than hard-coding the specific values seen in a video. It recognizes that a string of numbers in a specific box represents an "Account Balance" variable and generates the React code with appropriate props and state management to handle that data dynamically.

Can Replay modernize systems without the original source code?#

Yes. That is the core strength of Visual Reverse Engineering. Because Replay analyzes the visual output of the application, it does not need access to the underlying COBOL, Java, or .NET source code. This makes it the perfect solution for systems where the source code is lost, undocumented, or too complex to parse.

Is live interaction profiling using AI secure for government use?#

Absolutely. Replay offers on-premise deployments and is SOC2 and HIPAA-ready. It includes features specifically designed for regulated industries, such as automated PII masking and local-only processing of video data, ensuring that no sensitive information ever leaves the secure environment.

How much time does Replay actually save?#

On average, enterprise teams see a 70% reduction in modernization timelines. A process that typically takes 18 months—from discovery to deployment—can be compressed into a matter of weeks by automating the most labor-intensive parts of the lifecycle: documentation, design system creation, and UI coding.

---

Ready to modernize without rewriting? Book a pilot with Replay