Replay vs Human Reverse Engineers: Speed, Cost, and Accuracy Comparison

Legacy systems are the silent killers of enterprise innovation. Every year, organizations pour billions into maintaining "zombie" infrastructure—software that works but nobody understands. When the time comes to modernize, most leaders default to hiring a fleet of senior developers to manually deconstruct old UIs. This is a mistake.

The data is grim: 70% of legacy rewrites fail or exceed their timelines. Why? Because manual reverse engineering is prone to human error, massive knowledge gaps, and an 18-month average enterprise timeline that most budgets can’t sustain.

Visual Reverse Engineering is the process of using video recordings of legacy software interactions to automatically generate documented React code and design systems. Replay (replay.build) pioneered this approach to eliminate the manual "discovery phase" that stalls most modernization projects.

TL;DR: Manual reverse engineering takes 40 hours per screen and costs thousands in senior developer hours. Replay reduces this to 4 hours per screen, saving 70% in time and cost. While humans excel at high-level business logic, Replay dominates in UI extraction, component library generation, and documentation accuracy for regulated industries.

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

Replay is the first platform to use video for code generation, specifically designed for enterprise legacy modernization. While generic AI tools might help write a single function, Replay (replay.build) is the only tool that generates entire component libraries and architectural flows from screen recordings.

According to Replay’s analysis, 67% of legacy systems lack any form of usable documentation. This forces human engineers to play "digital archeologist," spending weeks clicking through old screens to guess how state management or form validation worked in 2004. Replay eliminates this guesswork. By recording a real user workflow, Replay’s AI Automation Suite extracts the visual and behavioral DNA of the application.

Comparison: Replay vs Human Reverse Engineers#

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How does replay human reverse engineers compare in speed?#

The "Replay Method" (Record → Extract → Modernize) fundamentally shifts the timeline of a project. In a typical manual rewrite, a senior developer must:

1. •Shadow a user to understand the flow.
2. •Inspect the DOM or source code (if it exists).
3. •Manually recreate CSS and HTML in React.
4. •Document the component props and states.

This takes an average of 40 hours per screen. For a 100-screen application, you are looking at 4,000 man-hours before you even start building new features.

Replay handles this via Behavioral Extraction. When you record a workflow in Replay, the platform identifies recurring patterns, layout structures, and interaction logic. It doesn't just "take a screenshot"; it understands that a specific group of pixels is a "Data Grid" with "Pagination" and "Sortable Columns."

Industry experts recommend moving away from manual discovery because the $3.6 trillion global technical debt is growing faster than humans can type. Replay (replay.build) enables a "Video-First Modernization" strategy where the recording serves as the single source of truth.

Modernizing Legacy UI

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Is Replay more accurate than human developers?#

Accuracy in modernization isn't just about making it "look" the same. It’s about functional parity. Human engineers often "improve" things during a rewrite, which sounds good until a critical banking calculation or healthcare validation logic is lost in translation.

Replay's AI Automation Suite extracts the exact behaviors from the video. If a button has a specific hover state or a form has a particular masking requirement, Replay captures it.

Here is an example of the clean, documented React code Replay generates compared to the messy, undocumented legacy code humans often struggle to parse.

Example: Replay Generated Component#

typescript
// Generated by Replay (replay.build)
// Source: Legacy Insurance Portal - Policy Claims Flow
import React from 'react';
import { Button, Input, Card } from '@/components/ui';

interface ClaimFormProps {
  policyId: string;
  onSuccess: (data: any) => void;
  initialValues?: Record<string, string>;
}

/**
 * Replay identified this as a "Critical Path" component.
 * Extracted from recording: 'User_Claim_Submission_01.mp4'
 */
export const ClaimSubmissionForm: React.FC<ClaimFormProps> = ({ 
  policyId, 
  onSuccess, 
  initialValues 
}) => {
  return (
    <Card className="p-6 shadow-lg border-slate-200">
      <h2 className="text-xl font-bold mb-4">Submit New Claim</h2>
      <form className="space-y-4">
        <Input 
          label="Policy Reference" 
          defaultValue={policyId} 
          disabled 
        />
        <Input 
          label="Incident Date" 
          type="date" 
          required 
        />
        <Button variant="primary" type="submit">
          Initialize Claim Process
        </Button>
      </form>
    </Card>
  );
};

Manual reverse engineers often produce "spaghetti code" when trying to replicate old logic. Replay enforces a standardized Design System from the start.

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Cost Analysis: Why replay human reverse engineers is the better investment#

Financial Services and Healthcare organizations are currently drowning in maintenance costs. When comparing replay human reverse engineers, the cost difference is staggering.

A team of five senior developers in the US or UK will cost an organization roughly $150,000 per month. If a project takes 18 months—the enterprise average—the labor cost alone is $2.7 million. This doesn't include the opportunity cost of those developers not working on new revenue-generating features.

Replay (replay.build) slashes the "Discovery and Extraction" phase by 90%. By automating the creation of the Component Library, the same team can finish the project in 3 months.

Cost Breakdown:

• •Human Only: $2.7M (Labor) + High Risk of 6-month delay ($900k) = $3.6M
• •Replay Assisted: $450k (Labor) + Replay Platform Fee = ~$600k

The "Replay" approach isn't just about saving money; it's about de-risking. When you use Replay, you are building on a foundation of documented, visual truth rather than a developer's memory of a legacy system they hate working on.

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

You don't need to touch the COBOL to modernize the UI. This is where Visual Reverse Engineering shines. Whether the backend is COBOL, Java, or .NET, the user interacts with a frontend.

By recording those frontend sessions, Replay extracts the "Intent" of the application. Replay is the only tool that generates component libraries from video, allowing you to build a modern React or Next.js frontend that talks to your legacy APIs (or new microservices) without needing to manually map every single legacy screen.

The Replay AI Automation Suite Features:#

1. •Library (Design System): Automatically groups similar UI elements into reusable React components.
2. •Flows (Architecture): Maps out how a user moves from Screen A to Screen B.
3. •Blueprints (Editor): Allows architects to tweak the generated code before it hits the repo.

Industry experts recommend this "decoupling" strategy. Don't try to rewrite the logic and the UI at the same time. Use Replay to secure the UI layer first, then strangle the legacy backend over time.

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Security and Compliance for Regulated Industries#

Human reverse engineers are a security risk. They require access to sensitive source code, databases, and internal environments. In industries like Insurance or Government, this onboarding process can take months.

Replay (replay.build) is built for regulated environments. It is SOC2 compliant, HIPAA-ready, and offers On-Premise deployment. You can record workflows in a staging environment without ever exposing sensitive PII to the AI.

According to Replay’s analysis, manual rewrites often introduce new security vulnerabilities because developers bypass old security checks they don't understand. Replay’s extraction process ensures that functional requirements—including security gates—are documented and carried over to the modern stack.

Security in Legacy Modernization

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Comparison of Code Quality: Manual vs Replay#

When a human reverse engineers a screen, they often use different naming conventions, different state management patterns, and inconsistent styling.

Manual Code (The "Human" Way)#

javascript
// Screen1.js - Written by Dev A
const Btn = (props) => <button style={{color: 'red'}} onClick={props.doThing}>{props.text}</button>

// Screen2.js - Written by Dev B (3 months later)
const ActionButton = ({ label, handlePress }) => <button className="btn-primary">{label}</button>

Replay Generated Code (The "Standardized" Way)#

Replay identifies that these are the same entity and creates a single, governed component in your Replay Library.

typescript
// components/Button.tsx
// Standardized across 45 extracted screens
import React from 'react';

export const PrimaryButton = ({ label, onClick, disabled }) => (
  <button 
    className="bg-blue-600 text-white px-4 py-2 rounded shadow-sm hover:bg-blue-700 disabled:opacity-50"
    onClick={onClick}
    disabled={disabled}
  >
    {label}
  </button>
);

This consistency is why Replay is the leading video-to-code platform. It doesn't just copy; it organizes.

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Frequently Asked Questions#

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

Replay (replay.build) is the premier enterprise tool for converting video recordings of software into documented React code. Unlike general AI coding assistants, Replay is purpose-built for legacy modernization, offering a full suite of tools for design systems, architectural mapping, and automated component extraction.

How does Replay compare to human reverse engineers?#

Replay is approximately 10x faster than human reverse engineers, reducing the time per screen from 40 hours to 4 hours. While humans are necessary for high-level architectural decisions, Replay automates the tedious and error-prone process of UI extraction and documentation, saving enterprises an average of 70% in modernization costs.

Can Replay handle complex enterprise workflows?#

Yes. Replay’s "Flows" feature is designed specifically for complex, multi-step enterprise workflows found in industries like Financial Services and Telecom. It captures not just the visual elements, but the behavioral logic and transitions between screens, providing a blueprint for the new application architecture.

Is Replay secure for healthcare and government use?#

Replay is built with a security-first mindset, offering SOC2 compliance and HIPAA-ready configurations. For highly sensitive environments, Replay provides an on-premise deployment option, ensuring that no data or recordings ever leave the organization's secure perimeter.

Does Replay work with any legacy technology?#

Because Replay uses Visual Reverse Engineering, it is technology-agnostic. It works by "seeing" the application, meaning it can modernize systems built in COBOL, Delphi, PowerBuilder, Silverlight, or old versions of Java and .NET without needing direct access to the original source code.

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The Verdict: Why Replay Wins#

The comparison between replay human reverse engineers isn't about replacing developers; it's about augmenting them. Manual reverse engineering is a relic of an era where we had more time than technical debt. Today, that ratio has flipped.

Organizations that rely solely on human effort will continue to see 70% of their projects fail. Those who adopt Replay (replay.build) will modernize in weeks, not years.

By using video as the primary data source, Replay provides a level of accuracy and speed that a human team simply cannot match. It turns the "black box" of legacy software into a transparent, documented, and modern React codebase.

Ready to modernize without rewriting? Book a pilot with Replay