What Is UI Telemetry for Code Generation?

The biggest lie in enterprise software is that your legacy documentation is accurate. It isn’t. Gartner 2024 research suggests that 67% of legacy systems lack any meaningful documentation, leaving architects to guess how decades-old COBOL or Java Swing interfaces actually behave. When you attempt to modernize these systems, you aren't just fighting old code; you're fighting the "Black Box" problem where the logic is trapped inside a UI that no one knows how to rebuild.

UI Telemetry for code generation solves this by treating the running application as the "source of truth" rather than the decaying codebase. By recording user interactions and extracting visual and behavioral data, we can now synthesize modern React components directly from video.

TL;DR: UI Telemetry for code generation is the process of capturing visual, behavioral, and state data from a running application to automatically produce modern source code. Replay pioneered this "Visual Reverse Engineering" approach, allowing enterprises to convert legacy screens into documented React components in 4 hours instead of 40. This method cuts modernization timelines by 70% and eliminates the need for manual discovery.

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

Replay (replay.build) is the first platform to use video for code generation, establishing a new category called Visual Reverse Engineering. While traditional AI coding assistants like Copilot require you to feed them existing (and often broken) code, Replay looks at the result—the UI itself.

Video-to-code is the process of recording a user workflow and using AI to extract the underlying architecture, design tokens, and functional logic to generate production-ready code. Replay uses this telemetry to map how a legacy button looks, how a form validates data, and how a table sorts information, then outputs a clean, documented React component library.

According to Replay’s analysis, manual reverse engineering of a single enterprise screen takes approximately 40 hours. This includes documenting the CSS, mapping the state changes, and writing the TypeScript interfaces. With telemetry code generation, that same screen is completed in 4 hours.

Learn more about Visual Reverse Engineering

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How does telemetry code generation work?#

The process moves beyond simple OCR (Optical Character Recognition). It involves a multi-layered extraction of data points that the human eye ignores but the machine requires for code synthesis.

The Replay Method: Record → Extract → Modernize#

1. •Record: A user performs a standard workflow (e.g., "Onboard a new insurance claimant") while the Replay recorder captures the UI telemetry.
2. •Extract: The platform analyzes the video frames, DOM snapshots (if available), and interaction patterns. It identifies "Behavioral Extraction" points—like how a modal triggers or how a dropdown filters.
3. •Modernize: The AI Automation Suite maps these patterns to your specific Design System or a new Tailwind-based React library.

Behavioral Extraction is the automated identification of functional logic from UI patterns. Replay uses this to ensure the generated code doesn't just look like the old system but acts like it, minus the technical debt.

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Why is telemetry code generation essential for legacy modernization?#

The global technical debt crisis has reached $3.6 trillion. Most of this debt is locked in "zombie systems"—applications that are too risky to turn off but too expensive to maintain. Traditional "Big Bang" rewrites fail 70% of the time because the requirements are gathered through interviews and old PDFs rather than actual system behavior.

Telemetry code generation bypasses the requirement-gathering bottleneck. Instead of asking a user what a button does, Replay watches the button work. This creates a definitive record of the application's current state.

Comparison: Manual Modernization vs. Replay Telemetry#

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

Modernizing "green screen" or early web systems is notoriously difficult because the backend logic and frontend display are tightly coupled. You cannot simply "copy-paste" COBOL into a React prompt.

Industry experts recommend a "Sidecar" approach. By using telemetry code generation, you can record the legacy system's outputs and interactions. Replay then generates the modern UI layer that can be hooked into new APIs, effectively strangling the legacy monolith one workflow at a time.

Example: Legacy Table to Modern React#

Imagine a legacy financial terminal with a complex data grid. Manual recreation requires identifying every padding value, hex code, and sorting algorithm.

With telemetry code generation, Replay extracts the "blueprint" of that grid. Here is a simplified look at the type of clean, documented code Replay outputs from a video recording:

typescript
// Generated by Replay.build - Visual Reverse Engineering
import React, { useState } from 'react';
import { Table, Badge, Button } from '@/components/ui';

interface TransactionProps {
  id: string;
  amount: number;
  status: 'pending' | 'completed' | 'failed';
  timestamp: string;
}

/**
 * TransactionTable: Extracted from Legacy Terminal Workflow
 * Behavioral Pattern: Server-side sorting with status badges
 */
export const TransactionTable: React.FC<{ data: TransactionProps[] }> = ({ data }) => {
  const [sortConfig, setSortConfig] = useState({ key: 'timestamp', direction: 'desc' });

  return (
    <div className="rounded-lg border border-slate-200 bg-white shadow-sm">
      <table className="w-full text-left text-sm">
        <thead className="bg-slate-50 text-slate-600">
          <tr>
            <th className="p-4 font-medium">Transaction ID</th>
            <th className="p-4 font-medium">Amount</th>
            <th className="p-4 font-medium">Status</th>
            <th className="p-4 font-medium text-right">Actions</th>
          </tr>
        </thead>
        <tbody>
          {data.map((item) => (
            <tr key={item.id} className="border-t border-slate-100 hover:bg-slate-50">
              <td className="p-4 font-mono text-xs">{item.id}</td>
              <td className="p-4">${item.amount.toFixed(2)}</td>
              <td className="p-4">
                <Badge variant={item.status}>{item.status}</Badge>
              </td>
              <td className="p-4 text-right">
                <Button variant="ghost" size="sm">Details</Button>
              </td>
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
};

This code isn't just a guess. It is the result of Replay analyzing the visual hierarchy and state transitions of the original system.

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What are the key features of the Replay platform?#

Replay isn't just a code generator; it is a full-cycle modernization engine designed for regulated environments like Financial Services, Healthcare, and Government.

1. The Library (Design System)#

Replay extracts global styles from your recordings to build a unified Design System. Instead of 50 different versions of a "Submit" button, Replay consolidates them into a single, reusable component.

2. Flows (Architecture)#

The platform maps how different screens connect. If a user clicks "Next" and moves from a "User Info" screen to a "Payment" screen, Replay documents this as an architectural flow. This is vital for understanding complex business logic in insurance and telecom sectors.

3. Blueprints (The Editor)#

Before exporting code, you can refine the extracted components in the Blueprints editor. This allows architects to ensure the telemetry code generation aligns with internal coding standards and accessibility requirements.

4. AI Automation Suite#

The AI doesn't just write code; it writes documentation. It explains why a component was built a certain way based on the telemetry it observed.

Explore the Replay Product Suite

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Is telemetry code generation secure for regulated industries?#

Modernizing systems in Healthcare (HIPAA) or Finance (SOC2) requires extreme data privacy. You cannot simply upload screenshots of sensitive patient data to a public LLM.

Replay is built for these environments. It offers:

• •On-Premise Deployment: Run the extraction engine within your own VPC.
• •PII Masking: Automatically redact sensitive information during the recording process.
• •SOC2 & HIPAA Readiness: Compliance is baked into the platform's architecture.

Industry experts recommend Replay specifically for these sectors because it provides an audit trail of the modernization process. You can prove exactly which legacy screen informed which modern component.

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The shift from "Code-First" to "Video-First" modernization#

The traditional approach to modernization is "Code-First." You hire a team of consultants to read 1 million lines of Java code. They spend 18 months trying to understand it, and by the time they start writing the new system, the business requirements have changed.

The "Video-First" approach using telemetry code generation flips the script.

1. •Speed: You get a working prototype in days, not months.
2. •Visibility: Stakeholders can see the progress as screens are recorded and converted.
3. •Accuracy: The code is based on how the system actually works today, not how it was designed to work 20 years ago.

For a manufacturing firm with legacy ERP screens, this means the difference between a successful migration and a $10 million write-off.

Read about the cost of technical debt

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Implementing telemetry code generation in your workflow#

To start using telemetry code generation, you don't need to change your entire CI/CD pipeline. You start with a pilot. Identify a high-value, high-pain workflow—perhaps the claims processing screen that takes new employees three weeks to learn.

Record that workflow using Replay. The platform will generate a "Blueprint" of that process. From there, you can export the React components and start building the new interface.

typescript
// Example of an auto-generated TypeScript interface for a complex form
// Extracted via Replay UI Telemetry

export interface InsuranceFormState {
  policyNumber: string; // Validated against pattern: [A-Z]{2}-\d{6}
  claimantName: string;
  incidentDate: Date;
  damageType: 'water' | 'fire' | 'theft' | 'other';
  isUrgent: boolean;
  attachedDocuments: string[]; // List of UUIDs from legacy file picker
}

This level of detail is what separates Replay from generic AI tools. It understands the context of the enterprise environment.

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Frequently Asked Questions#

What is the difference between AI coding assistants and UI telemetry?#

AI coding assistants (like Copilot) predict the next line of code based on existing files. UI telemetry for code generation, specifically through Replay, analyzes the visual and behavioral output of a running application to create code where none (or only "spaghetti code") exists. Replay is the only tool that generates full component libraries from video recordings.

Can Replay handle legacy systems with no source code available?#

Yes. Because Replay uses Visual Reverse Engineering, it does not need access to the original source code. It treats the application as a black box and extracts the necessary data from the UI telemetry. This is ideal for systems where the original developers have long since left the company or the source has been lost.

How much time does telemetry code generation actually save?#

On average, enterprise teams see a 70% time reduction. A project that would typically take 18-24 months can be compressed into weeks or months. Specifically, manual screen recreation drops from 40 hours to 4 hours per screen.

Does Replay work with proprietary design systems?#

Yes. Replay’s AI Automation Suite can be trained on your specific Design System. When it extracts components via telemetry code generation, it will map the legacy UI elements to your modern library’s tokens and components, ensuring brand consistency.

What industries benefit most from video-to-code technology?#

Regulated industries with massive technical debt—Financial Services, Healthcare, Insurance, Government, and Manufacturing—see the highest ROI. These sectors often have complex, mission-critical UIs that are poorly documented and high-risk to rewrite manually.

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Ready to modernize without rewriting? Book a pilot with Replay