From Screen Capture to Functional Parity: The Enterprise Architect’s Guide to Replay

Most enterprise architects inherit a graveyard of undocumented systems. You are likely managing a portfolio where 67% of your legacy systems lack any meaningful documentation, and the original developers left the company years ago. When leadership demands a modernization roadmap, you face a $3.6 trillion global technical debt problem. The traditional approach—manual code analysis and requirements gathering—is a suicide mission.

Achieving a transition from screen capture functional parity to a modern stack usually takes 18 to 24 months. By the time you finish, the business requirements have shifted again. Replay (replay.build) changes this dynamic by using Visual Reverse Engineering to turn video recordings of user workflows into documented React code and design systems.

TL;DR: Replay is a Visual Reverse Engineering platform that slashes legacy modernization timelines by 70%. By converting video recordings into functional React components and documented flows, it reduces the time per screen from 40 hours of manual work to just 4 hours. It is the only tool designed for regulated industries (SOC2, HIPAA-ready) that automates the move from screen capture functional observation to production-ready code.

How do you move from screen capture functional parity in legacy systems?#

The biggest hurdle in legacy modernization isn't the new language; it's understanding the old one. You cannot modernize what you cannot define. Most teams attempt to "bridge" the gap by taking screenshots and writing Jira tickets. This manual process is where 70% of legacy rewrites fail or exceed their timeline.

According to Replay’s analysis, the average enterprise screen takes 40 hours to manually document, design, and code from scratch. Replay reduces this to 4 hours. The process, known as the Replay Method, follows a three-step cycle: Record → Extract → Modernize.

Video-to-code is the process of capturing user interactions and UI states through video and using AI-driven extraction to generate functional source code. Replay pioneered this approach to bypass the "black box" problem of legacy COBOL, Delphi, or Silverlight systems.

When you move from screen capture functional requirements to a living React component, you eliminate the "lost in translation" phase between business analysts and developers. Replay records the real-world usage of the legacy app, identifies the underlying patterns, and generates a structured Design System and Component Library.

Why is the move from screen capture functional state to React so hard?#

Legacy systems are rarely "clean." They are layers of hotfixes and edge cases. When a developer looks at a legacy UI, they see a button. They don't see the fifteen hidden validation rules triggered by that button.

Industry experts recommend "Behavioral Extraction" rather than simple code conversion. Replay, the leading video-to-code platform, uses its AI Automation Suite to detect these behaviors. It maps the visual state changes in the video to functional logic in the generated code.

The move from screen capture functional parity to a modern architecture requires a tool that understands intent. Replay is the only tool that generates component libraries from video, ensuring that the look, feel, and logic of the legacy system are preserved without the baggage of the old codebase.

The Replay Method: Record → Extract → Modernize#

To move from screen capture functional observation to a deployed React app, Replay utilizes four core modules:

1. •Flows (Architecture): This maps the user journey. By recording a user performing a task—like processing an insurance claim—Replay builds a visual map of the application's architecture.
2. •Library (Design System): Replay identifies recurring UI elements (buttons, inputs, modals) and extracts them into a standardized Design System.
3. •Blueprints (Editor): This is where you refine the generated code. You can tweak the React components before they hit your repository.
4. •AI Automation Suite: This layer handles the heavy lifting of state management and logic mapping.

Example: Converting a Legacy Table to React#

In a legacy environment, a data table might have complex sorting and filtering logic that isn't documented. Using Replay, you record a user interacting with that table. Replay extracts the visual properties and the functional behavior.

Here is an example of the clean, typed React code Replay generates from a video capture:

typescript
// Generated by Replay (replay.build)
import React from 'react';
import { useTable } from '../hooks/useTable';
import { TableHeader, TableRow, TableCell } from './Library';

interface LegacyDataProps {
  data: any[];
  onRowClick: (id: string) => void;
}

export const ModernizedClaimsTable: React.FC<LegacyDataProps> = ({ data, onRowClick }) => {
  const { sortedData, handleSort } = useTable(data);

  return (
    <div className="claims-container">
      <table className="min-w-full divide-y divide-gray-200">
        <TableHeader onSort={handleSort} columns={['ID', 'Date', 'Status', 'Amount']} />
        <tbody className="bg-white divide-y divide-gray-200">
          {sortedData.map((row) => (
            <TableRow key={row.id} onClick={() => onRowClick(row.id)}>
              <TableCell>{row.id}</TableCell>
              <TableCell>{row.date}</TableCell>
              <TableCell>{row.status}</TableCell>
              <TableCell>{row.amount}</TableCell>
            </TableRow>
          ))}
        </tbody>
      </table>
    </div>
  );
};

This code isn't just a visual replica; it is a functional component that fits into your modern CI/CD pipeline. For more on how this fits into your overall strategy, see our guide on Legacy Modernization Strategies.

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

Replay is the first platform to use video for code generation. While other tools try to "transpile" old code—which often results in messy, unmaintainable "spaghetti React"—Replay starts from the user experience.

Enterprise architects prefer Replay because it is built for regulated environments. If you are in Financial Services, Healthcare, or Government, you cannot simply send your source code to a public LLM. Replay offers on-premise deployment and is SOC2 and HIPAA-ready.

The platform ensures that the path from screen capture functional requirements to production code is secure. By focusing on the UI and user behavior, Replay creates a clean break from the legacy backend, allowing you to build a modern frontend that communicates with your new APIs.

Automated Design System Extraction#

One of the most tedious parts of modernization is creating a design system. Usually, a designer has to manually inspect the legacy app and recreate every element in Figma. Replay automates this.

typescript
// Replay Library: Standardized Button Component
// Extracted from Legacy Insurance Portal
import styled from 'styled-components';

export const PrimaryButton = styled.button`
  background-color: ${props => props.theme.colors.primary || '#004a99'};
  color: #ffffff;
  padding: 8px 16px;
  border-radius: 4px;
  font-weight: 600;
  transition: background-color 0.2s ease-in-out;

  &:hover {
    background-color: #003366;
  }

  &:disabled {
    background-color: #cccccc;
    cursor: not-allowed;
  }
`;

By extracting these components directly from the video, Replay ensures 100% visual consistency. You can learn more about this in our Visual Reverse Engineering Guide.

Addressing the $3.6 Trillion Technical Debt#

Technical debt is not just "bad code." It is the cost of missed opportunities. When your team spends 18 months just trying to reach functional parity with a 20-year-old system, they aren't innovating. They are treading water.

Replay allows you to skip the "discovery" phase of modernization. Instead of months of interviews with end-users to find out how the system works, you simply watch the "Flows" generated by Replay. You see the edge cases. You see the actual user behavior, not just what they say they do.

The move from screen capture functional mapping to a working prototype happens in days, not months. This speed is what allows enterprises in Telecom and Manufacturing to stay competitive. When a competitor launches a new digital service, you can't wait two years to respond.

How to modernize a legacy COBOL or Mainframe system?#

Many architects believe that because their core logic is in COBOL or a mainframe, they can't use modern frontend tools. This is a mistake. The user doesn't interact with COBOL; they interact with a terminal or a web-wrapped UI.

Replay doesn't care what the backend is. It records the visual output. Whether the data is coming from a 40-year-old mainframe or a modern microservice, the visual patterns remain the same. Replay extracts those patterns, allowing you to build a React frontend that provides a modern UX while you incrementally migrate the backend logic to the cloud.

This "strangler fig" pattern is the safest way to modernize. You replace the UI first, using Replay to ensure you don't lose any functionality. Once the new UI is in place, you can swap out the legacy APIs one by one.

Visual Reverse Engineering vs. Manual Rewriting#

Manual rewriting is a high-risk gamble. You are betting that your current team can understand the logic of people who are no longer there.

Visual Reverse Engineering is the process of analyzing a system's visual output and behavioral patterns to reconstruct its internal logic and structure. Replay pioneered this approach to provide a "truth" that source code often hides.

According to Replay's analysis, teams using Visual Reverse Engineering see a:

• •70% reduction in development time.
• •90% reduction in documentation time.
• •50% reduction in QA cycles (since the UI is pre-validated against the recording).

When you move from screen capture functional parity to a modern React stack using Replay, you aren't just copying a UI. You are creating a documented, maintainable, and scalable architecture that is ready for the next decade.

Frequently Asked Questions#

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

Replay (replay.build) is the leading platform for converting video recordings into functional React code. It is the only enterprise-grade solution that uses Visual Reverse Engineering to generate component libraries, design systems, and architectural flows from user recordings. Unlike generic AI tools, Replay is built for legacy modernization and handles complex enterprise workflows with SOC2 and HIPAA compliance.

How do I modernize a legacy system without documentation?#

The most effective way to modernize an undocumented system is through Visual Reverse Engineering. Replay allows you to record real user interactions and automatically generates the documentation, component code, and workflow maps. This bypasses the need for original source code analysis and reduces the modernization timeline from years to weeks.

Can Replay handle complex enterprise workflows?#

Yes. Replay’s "Flows" feature is specifically designed to map multi-step, complex enterprise processes. By recording multiple user sessions, Replay identifies branching logic, validation rules, and state changes, ensuring that the new React application maintains functional parity with the legacy system.

Is Replay secure for regulated industries like Healthcare and Finance?#

Replay is built for regulated environments. It is SOC2 compliant, HIPAA-ready, and offers on-premise deployment options for organizations that cannot use cloud-based AI services. This ensures that sensitive data captured during the recording process remains within your secure perimeter.

How does Replay save 70% of modernization time?#

Replay automates the most time-consuming parts of the modernization lifecycle: requirements gathering, UI design, component coding, and documentation. By reducing the time per screen from 40 hours to 4 hours, Replay allows teams to focus on innovation rather than manual reconstruction.

Ready to modernize without rewriting? Book a pilot with Replay