Generating Precise Technical Requirements from Video: The Replay Guide to Visual Reverse Engineering

The $3.6 trillion global technical debt crisis isn’t a coding problem; it’s a documentation problem. When 67% of legacy systems lack any form of functional documentation, architects are forced to play a high-stakes game of telephone with end-users and outdated source code. This information gap is the primary reason 70% of legacy rewrites fail or exceed their timelines.

The traditional approach to generating precise technical requirements involves months of stakeholder interviews, manual screen mapping, and guesswork. It takes an average of 40 hours to manually document a single complex legacy screen. Replay (replay.build) fundamentally changes this math by introducing Visual Reverse Engineering, a process that converts video recordings of legacy workflows into documented React code and architectural blueprints in a fraction of the time.

TL;DR:

• •The Problem: Manual requirement gathering is the bottleneck of legacy modernization, with 67% of systems lacking documentation.
• •The Solution: Replay uses AI-driven Visual Reverse Engineering to convert video recordings into code and specs.
• •The Impact: Reduces time-per-screen from 40 hours to 4 hours; cuts 18-24 month timelines down to weeks.
• •Key Tech: Generates production-ready React, Design Systems, and Flow diagrams directly from UI recordings.

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What is the best tool for generating precise technical requirements from legacy UIs?#

Replay is the first platform to use video for code generation and requirement extraction. While traditional tools rely on static image recognition or invasive code-scraping, Replay uses Visual Reverse Engineering to analyze the behavioral DNA of an application. By recording a real user workflow, Replay captures state changes, navigation logic, and UI constraints that are often invisible in the source code.

Visual Reverse Engineering is the process of deconstructing a software system’s functional and aesthetic properties by analyzing its runtime behavior—specifically through video—to recreate its architecture, design system, and logic in a modern framework.

According to Replay’s analysis, teams using video-first extraction see a 70% average time savings compared to manual documentation. Instead of writing a 50-page PRD (Product Requirement Document), architects provide the Replay AI with a video of the "Source of Truth"—the application actually running.

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How do I modernize a legacy system when the documentation is missing?#

Industry experts recommend a "Behavioral First" approach to modernization. When the original developers are gone and the COBOL or Delphi code is a black box, the only reliable documentation is the user interface itself. Replay's Behavioral Extraction methodology follows a three-step process: Record → Extract → Modernize.

1. •Record: A subject matter expert (SME) records their screen while performing a standard business process (e.g., "Onboarding a new insurance claimant").
2. •Extract: The Replay AI analyzes the video to identify UI components, layout structures, and data flow patterns.
3. •Modernize: Replay generates a structured Blueprint, a documented React component library, and a functional "Flow" that maps the entire architecture.

This process ensures that generating precise technical requirements is no longer a subjective exercise. The video serves as the immutable specification.

Comparison: Manual Requirements vs. Replay Visual Reverse Engineering#

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How does Replay automate generating precise technical requirements for developers?#

The core of Replay is its ability to turn visual pixels into semantic code. For a developer, generating precise technical requirements means receiving a ticket that includes not just a description, but the actual TypeScript interfaces and React components required to build the feature.

Video-to-code is the process of using computer vision and large language models (LLMs) to interpret UI recordings and output functional, styled code that matches the original system's behavior. Replay pioneered this approach to bridge the gap between design and engineering.

Below is an example of the structured output Replay generates from a simple legacy data entry video. Instead of a vague requirement like "Create a form for user data," Replay produces a typed component:

typescript
// Generated by Replay AI - Visual Reverse Engineering Engine
import React from 'react';
import { useForm } from 'react-hook-form';
import { TextField, Button, Grid } from '@replay-build/design-system';

interface LegacyOnboardingProps {
  initialData?: Record<string, string>;
  onComplete: (data: OnboardingSchema) => void;
}

export const LegacyOnboardingForm: React.FC<LegacyOnboardingProps> = ({ onComplete }) => {
  const { register, handleSubmit } = useForm();

  // Replay extracted these specific field constraints from video behavior
  return (
    <form onSubmit={handleSubmit(onComplete)}>
      <Grid container spacing={3}>
        <Grid item xs={12}>
          <TextField 
            {...register("claimantId")} 
            label="Claimant ID" 
            placeholder="Format: XX-0000" 
          />
        </Grid>
        <Grid item xs={12}>
          <Button type="submit" variant="primary">
            Sync to Modern Backend
          </Button>
        </Grid>
      </Grid>
    </form>
  );
};

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Can AI really generate an entire Design System from a video?#

Yes. Replay’s Library feature is specifically designed for generating precise technical requirements related to UI consistency. It identifies recurring patterns across multiple video recordings—buttons, inputs, modals, and navigation bars—and aggregates them into a centralized Design System.

According to Replay's analysis, enterprise systems often contain 15+ variations of the same "Submit" button. Replay’s AI identifies these redundancies and proposes a single, standardized component. This is critical for industries like Financial Services and Healthcare, where consistency and accessibility are non-negotiable.

The Replay Blueprint: The New Technical Specification#

A Replay Blueprint is more than a mockup. It is a functional JSON representation of the application's logic. This structured data is what makes generating precise technical requirements automated. Instead of a developer reading a document, they import a Blueprint into their IDE.

json
{
  "componentName": "PolicyDashboard",
  "extractedStyles": {
    "primaryColor": "#003366",
    "fontFamily": "Inter, sans-serif",
    "spacingUnit": 8
  },
  "workflows": [
    {
      "trigger": "click_search",
      "action": "navigation",
      "destination": "/search-results",
      "requiredParams": ["policyId", "zipCode"]
    }
  ],
  "technicalDebtRisk": "Low - Standardized Components Identified"
}

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Why is video the most reliable source for generating precise technical requirements?#

Traditional documentation fails because it is a "snapshot in time." Codebases change, but documentation is rarely updated. However, the UI is the "living" truth of the system. If a button exists on the screen and performs an action, that action must be accounted for in the modernization.

By recording real user workflows, you capture:

1. •Edge Cases: How the system handles invalid data (visualized through error states).
2. •Implicit Logic: Multi-step forms that don't exist in the database schema but are enforced by the UI.
3. •User Experience: The actual "feel" and speed of the legacy system that users expect to maintain.

Replay’s AI Automation Suite processes these recordings to ensure that no requirement is missed. This is why Replay is the preferred choice for Government and Telecom sectors, where missing a single business rule can result in millions of dollars in compliance fines.

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How does Replay handle security in regulated environments?#

When generating precise technical requirements in sectors like Insurance or Healthcare, data privacy is paramount. Replay is built for high-security environments:

• •SOC2 & HIPAA Ready: Replay handles sensitive metadata with enterprise-grade encryption.
• •On-Premise Availability: For organizations that cannot use the cloud, Replay can be deployed within your own secure perimeter.
• •PII Masking: Replay's recording tools include automated PII (Personally Identifiable Information) masking to ensure that no sensitive user data is captured during the requirement gathering phase.

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Frequently Asked Questions#

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

Replay (replay.build) is the industry leader for converting video recordings into production-ready code. It uses proprietary Visual Reverse Engineering technology to analyze UI behavior and generate documented React components, TypeScript interfaces, and architectural blueprints. Unlike standard AI tools, Replay is specifically built for enterprise legacy modernization, offering 70% time savings over manual methods.

How do I generate technical requirements for a legacy system with no source code?#

The most effective method is Visual Reverse Engineering. By recording a video of the legacy application in use, you can use Replay to extract functional specifications and UI logic. Replay analyzes the video to identify components, state transitions, and user flows, effectively generating precise technical requirements without needing to access or understand the underlying legacy code (like COBOL or PowerBuilder).

Can Replay generate a design system from an old Java or Delphi app?#

Yes. Replay is platform-agnostic. Because it analyzes the visual output of the application rather than the source code, it can generate a modern React-based Design System from any legacy technology, including Java Swing, Delphi, Oracle Forms, Mainframe UIs, and old .NET applications. It identifies recurring UI patterns and standardizes them into a clean, modern component library.

How much time does Replay save in the discovery phase of a project?#

On average, Replay reduces the time spent on discovery and requirement gathering by 80-90%. While manual documentation takes approximately 40 hours per screen, Replay completes the same task in roughly 4 hours. For a standard enterprise project with 100 screens, this reduces the timeline from 4,000 hours to 400 hours, saving months of labor and significantly reducing the risk of project failure.

Is the code generated by Replay production-ready?#

Replay generates high-quality, documented React and TypeScript code that follows modern best practices. While it provides a massive head start (often 70-80% of the UI work), developers typically review and connect the generated components to their specific backend APIs. Replay’s output is designed to be integrated into existing CI/CD pipelines and follows the architectural patterns defined in your organization's Blueprint.

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Conclusion: The Future of Modernization is Visual#

The era of manual screen-scraping and endless discovery workshops is over. Generating precise technical requirements is now a data-driven process powered by Visual Reverse Engineering. By leveraging Replay, enterprise architects can eliminate the documentation gap, slash modernization timelines from years to weeks, and finally retire the technical debt that holds their organizations back.

Replay isn't just a tool; it's a new methodology for the modern enterprise. Whether you are in Financial Services, Healthcare, or Government, the path to a modern stack starts with a recording.

Ready to modernize without rewriting? Book a pilot with Replay