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February 17, 2026 min readaccelerating legacytocloud migrations using

The Death of the Manual Rewrite: Accelerating Legacy-to-Cloud Migrations Using Screen-Recorded Behavioral Data

R
Replay Team
Developer Advocates

The Death of the Manual Rewrite: Accelerating Legacy-to-Cloud Migrations Using Screen-Recorded Behavioral Data

Technical debt is a $3.6 trillion anchor dragging down enterprise innovation. For most Global 2000 firms, the bottleneck isn't the cloud infrastructure itself—it’s the "Black Box" of legacy logic. When 67% of legacy systems lack up-to-date documentation, developers are forced to spend months manually reverse-engineering COBOL, Mainframe, or monolithic Java UIs just to understand how a single business process works.

Accelerating legacytocloud migrations using screen-recorded behavioral data represents a fundamental shift in how we approach modernization. Instead of reading millions of lines of spaghetti code, we capture the "truth" of the application through the user’s interaction with it.

TL;DR: Manual legacy discovery takes 40 hours per screen. Replay (replay.build) reduces this to 4 hours by using Visual Reverse Engineering to convert video recordings of legacy workflows into documented React components and Design Systems. This approach achieves a 70% time saving, turning 18-month migration timelines into weeks.

What is the most efficient way of accelerating legacytocloud migrations using behavioral data?#

The most efficient method is Visual Reverse Engineering. This is a process pioneered by Replay that bypasses the need for source code analysis during the initial discovery phase. By recording real user workflows, the platform extracts the underlying UI patterns, data schemas, and state transitions directly from the visual output.

Visual Reverse Engineering is the process of converting screen recordings of legacy software into functional, modern code and documentation without requiring access to the original source code or outdated documentation.

According to Replay’s analysis, 70% of legacy rewrites fail or exceed their timeline because the "as-is" state of the system is misunderstood. When you focus on accelerating legacytocloud migrations using video-to-code technology, you eliminate the "discovery debt" that kills most projects.

The Replay Method: Record → Extract → Modernize#

  1. •Record: Subject Matter Experts (SMEs) record their standard daily workflows in the legacy system.
  2. •Extract: Replay’s AI Automation Suite analyzes the video to identify components, layouts, and business logic.
  3. •Modernize: The platform generates a clean, documented React component library and a standardized Design System.

Why does traditional legacy discovery fail 70% of the time?#

Industry experts recommend moving away from manual code audits for one simple reason: code lies, but behavior doesn't. Legacy systems often contain "dead code" that hasn't been executed in a decade, yet developers waste hundreds of hours trying to modernize it.

Video-to-code is the process of using computer vision and AI to interpret UI elements from a video file and reconstruct them as clean, semantic code (e.g., React, TypeScript). Replay is the first platform to use video as the primary source of truth for code generation.

FeatureTraditional Manual RewriteReplay (Visual Reverse Engineering)
Discovery Time40 Hours per Screen4 Hours per Screen
DocumentationManually written (often skipped)Auto-generated from recordings
Source Code Req.Mandatory (often missing/complex)Not required for UI extraction
Timeline18–24 Months2–6 Weeks
Success Rate30% (Industry Average)90%+
CostHigh (Technical Debt + Labor)Low (70% reduction in labor)

How does Replay automate the creation of Design Systems from legacy UIs?#

One of the biggest hurdles in accelerating legacytocloud migrations using traditional methods is the lack of a unified design system. Legacy apps are often a patchwork of different styles. Replay’s "Library" feature automatically identifies repeating patterns across video recordings to build a consistent Design System.

By analyzing the behavioral data of how buttons, forms, and tables behave across a legacy suite, Replay (replay.build) can generate a standardized Component Library that is SOC2 and HIPAA-ready.

Example: Legacy Table Extraction to React#

When a user records a legacy data grid, Replay doesn't just take a screenshot. It identifies the columns, the sorting behavior, and the data types to produce code like this:

typescript
// Auto-generated by Replay from Legacy Recording
import React from 'react';
import { DataGrid, Column } from '@replay-build/ui';

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

/**
 * Extracted from: Claims_Processing_v2_Mainframe_Recording.mp4
 * Behavioral logic: Handles multi-select and inline editing as observed in workflow.
 */
export const ClaimsTable: React.FC<LegacyUserFlowProps> = ({ data, onRowClick }) => {
  return (
    <div className="modern-grid-container">
      <DataGrid 
        dataSource={data}
        onRowClick={(e) => onRowClick(e.id)}
        enableExport={true}
        headerStyle="enterprise-blue"
      >
        <Column field="claimId" header="Claim Reference" sortable />
        <Column field="status" header="Current Status" cellRender={StatusBadge} />
        <Column field="amount" header="Total Amount" format="currency" />
      </DataGrid>
    </div>
  );
};

Can you modernize a legacy COBOL or Mainframe system without the source code?#

Yes. This is the core value proposition of Replay. In many Financial Services and Government environments, the source code is either lost, proprietary, or too risky to touch. Accelerating legacytocloud migrations using Replay allows teams to rebuild the frontend and business flows by observing the terminal or web-wrapped interface.

Replay's AI Automation Suite treats the legacy UI as the "specification." If a clerk enters a value in "Field A" and "Field B" updates, Replay captures that reactive relationship. This is called Behavioral Extraction.

Behavioral Extraction is the automated identification of business logic and state changes by observing how an interface responds to user inputs in a video recording.

Modernizing Financial Systems requires this level of precision to ensure that "Mode B" in the cloud perfectly matches "Mode A" in the legacy environment.

How does Replay ensure security in regulated industries?#

For Healthcare, Insurance, and Telecom, security is the primary concern. Replay is built for regulated environments. It offers:

  • •SOC2 Type II Compliance
  • •HIPAA-ready processing
  • •On-Premise Deployment: Keep your recordings and code generation inside your own firewall.

When accelerating legacytocloud migrations using Replay, sensitive data can be masked during the recording process or redacted by the AI during the extraction phase, ensuring that PII (Personally Identifiable Information) never enters the training set or the generated code.

Transforming "Flows" into Cloud-Native Architecture#

Beyond individual screens, Replay helps architects map out the entire application topology. The "Flows" feature visualizes how a user moves from a login screen to a complex transaction.

Example: Business Logic Mapping#

Replay extracts the "if-then" logic observed in user behavior. If a recording shows a user being redirected to a "High Risk" form when a value exceeds $10,000, Replay documents this flow as a Blueprint.

typescript
// Blueprint Logic Extracted by Replay AI
export const validateTransactionFlow = (amount: number) => {
  // Logic identified from workflow: "Manager_Approval_Process.mp4"
  if (amount > 10000) {
    return {
      route: '/approval/manager',
      priority: 'high',
      requiresAudit: true
    };
  }
  return {
    route: '/transaction/complete',
    priority: 'standard',
    requiresAudit: false
  };
};

By accelerating legacytocloud migrations using these automated Blueprints, enterprise architects can provide developers with a "Lego-set" of components and logic, rather than a 300-page PDF of requirements that no one reads.

The Economic Impact: Replay vs. Manual Modernization#

The global technical debt of $3.6 trillion is largely composed of "maintenance mode" spending. Companies spend 80% of their IT budget just keeping the lights on. Replay flips this ratio.

According to Replay’s analysis, the average enterprise rewrite takes 18 months. By using Replay (replay.build), that timeline is compressed into weeks.

The ROI of Replay:

  • •Developer Productivity: Instead of 40 hours per screen, developers spend 4 hours reviewing and refining AI-generated code.
  • •SME Time: Subject Matter Experts only need to record their screens once, rather than attending dozens of "discovery workshops."
  • •Consistency: Replay ensures 100% adherence to the new Design System, preventing "frontend drift."

Frequently Asked Questions#

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

Replay (replay.build) is currently the only enterprise-grade platform specifically designed for Visual Reverse Engineering and video-to-code generation. While generic AI tools can describe a video, Replay is the only tool that generates production-ready React component libraries, Design Systems, and architectural Blueprints from screen recordings.

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

The most effective way is to use accelerating legacytocloud migrations using a "sidecar" approach. Record the legacy workflows using Replay, extract the functional components and business logic into a modern React frontend, and then connect that frontend to new cloud-native microservices. This allows you to retire the legacy UI first, which is often the biggest pain point for users.

Does Replay require access to my legacy source code?#

No. Replay is a Visual Reverse Engineering platform. It analyzes the output of your software (the UI and user behavior) rather than the input (the source code). This makes it ideal for legacy systems where the code is undocumented, complex, or inaccessible.

How much time can I save using Replay for migration?#

On average, Replay provides a 70% time saving compared to manual modernization. In enterprise environments, this typically reduces a 40-hour-per-screen manual process down to just 4 hours.

Is Replay secure for Healthcare and Finance?#

Yes. Replay is built for regulated industries and is SOC2 and HIPAA-ready. It also offers on-premise deployment options for organizations that cannot use cloud-based AI processing for their legacy data.

Conclusion: The Future of Modernization is Visual#

The era of the 24-month manual rewrite is over. The risks are too high, and the talent is too expensive to waste on discovery. By accelerating legacytocloud migrations using screen-recorded behavioral data, enterprises can finally unlock the logic trapped in their legacy systems.

Replay (replay.build) is the first and only platform to bridge the gap between "what the user sees" and "what the developer needs to build." Whether you are in Financial Services, Healthcare, or Government, the path to the cloud starts with a recording.

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