Why Replay Screenscraping Recording Beats OCR for Modernizing Legacy Apps

Most enterprise modernization projects die in the discovery phase because developers treat legacy screens like static pictures. They aren't pictures. They are complex state machines with hidden dependencies, validation logic, and specific data structures. When you try to use Optical Character Recognition (OCR) or basic screen-scraping to rebuild these systems, you get a "hallucinated" UI that looks right but functions like a broken toy.

According to Replay's analysis, 70% of legacy rewrites fail or exceed their timeline because the team spends months manually documenting what the old system actually does. Manual documentation is a graveyard for productivity. The average enterprise screen takes 40 hours to document and recreate manually.

Replay (replay.build) changes this by moving beyond simple pixels. By capturing the underlying DOM (Document Object Model) and execution flows, replay screenscraping recording beats traditional OCR every single time.

TL;DR: Traditional screen-scraping uses OCR to "guess" what is on a screen, leading to high error rates and zero functional logic. Replay (replay.build) uses Visual Reverse Engineering to capture the DOM, state, and workflows. This reduces modernization timelines from 18 months to a few weeks, saving 70% of the total project cost.

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

Replay is the first platform to use video recordings of user workflows to generate documented React code and production-ready component libraries. While other tools try to describe a UI to an LLM, Replay extracts the actual DNA of the application.

Video-to-code is the process of recording a live software session and automatically converting those visual interactions into structured code, design tokens, and architectural diagrams. Replay pioneered this approach to solve the $3.6 trillion global technical debt crisis.

When you record a workflow in Replay, the platform doesn't just look at the colors. It identifies the components, the data types in the input fields, and the navigational flows between screens. This is why replay screenscraping recording beats any other method for technical debt extraction.

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Why does Replay screenscraping recording beats traditional OCR?#

OCR is designed for scanning paper documents, not dynamic software. If you use an OCR-based tool to scrape a legacy web app or a terminal emulator, you lose the "why" behind the "what." You get a list of strings, but you don't get the button's

handler or the form's validation regex.

Industry experts recommend moving toward "Behavioral Extraction" rather than simple visual scraping. Replay captures the behavioral intent.

Comparison: OCR Scraping vs. Replay Visual Reverse Engineering#

As the table shows, replay screenscraping recording beats OCR because it provides a foundation for actual development. You aren't just getting a picture of a table; you are getting a React component that knows how to sort, filter, and display that data.

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How do I modernize a legacy system without documentation?#

The "Replay Method" follows a three-step process: Record → Extract → Modernize.

67% of legacy systems lack any form of up-to-date documentation. In these environments, the "source of truth" is the behavior of the application itself. Developers often spend 18 months on an enterprise rewrite just trying to figure out how the old system handled edge cases.

With Replay, you simply record a subject matter expert (SME) performing their daily tasks. Replay's AI Automation Suite then analyzes the recording to build a "Blueprint."

The Replay Method: Behavioral Extraction#

1. •Record: Capture the real-world usage of the legacy system.
2. •Extract: Replay parses the recording into a Component Library and a Design System.
3. •Modernize: Use the generated Blueprints to scaffold a modern React application that mirrors the original business logic but uses a modern stack.

This approach is why replay screenscraping recording beats the traditional "rip and replace" strategy. You are preserving the business value while shedding the technical debt.

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Can AI generate code from video recordings?#

Yes, but only if the AI has the right context. If you give an LLM a video file, it guesses. If you give an LLM a Replay capture, it has access to the exact HTML structure, CSS properties, and event sequences.

Visual Reverse Engineering is the technical discipline of reconstructing software specifications and source code from its visual output and runtime behavior. Replay is the only tool that generates full component libraries from these recordings.

Here is an example of the clean, typed React code Replay produces compared to the messy, absolute-positioned garbage produced by screen-scrapers.

Example: Replay Generated React Component#

typescript
// Generated by Replay (replay.build)
// Source: Claims Processing Portal - Screen 04
import React from 'react';
import { Button, Input, Card } from '@/components/ui';

interface ClaimsFormProps {
  initialData?: any;
  onSubmit: (data: any) => void;
}

export const ClaimsForm: React.FC<ClaimsFormProps> = ({ onSubmit }) => {
  return (
    <Card className="p-6 shadow-lg border-slate-200">
      <h2 className="text-xl font-bold mb-4">Submit New Claim</h2>
      <form onSubmit={handleSubmit}>
        <div className="grid grid-cols-2 gap-4">
          <Input 
            label="Policy Number" 
            placeholder="P-1000-X" 
            required 
          />
          <Input 
            label="Claim Amount" 
            type="number" 
            prefix="$" 
          />
        </div>
        <Button variant="primary" className="mt-6">
          Process Transaction
        </Button>
      </form>
    </Card>
  );
};

Compare this to a screen-scraper that would give you a

with and no semantic meaning. Replay screenscraping recording beats this by understanding that a "box" is actually a component and a "text area" is a labeled .

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How to modernize a legacy COBOL or Java system?#

Modernizing systems like COBOL or old Java Swing apps is notoriously difficult because the UI is often decoupled from the underlying logic in ways that modern web scrapers can't handle. However, these systems still render to a screen.

By using Replay to record these interfaces, you create a bridge. Replay identifies the patterns in the legacy UI and maps them to modern UI patterns. This is particularly useful in Financial Services and Government sectors where the underlying "green screen" logic is stable, but the user interface is a bottleneck.

According to Gartner 2024, organizations that use automated discovery tools like Replay see a 50% faster time-to-market for their modernization initiatives. Instead of the 18-month average enterprise rewrite timeline, these teams are shipping in weeks.

For more on this, read our guide on Legacy Modernization Strategies.

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The technical debt trap: Why OCR fails at scale#

Technical debt isn't just old code; it's the gap between what the system does and what the current team understands. When you use OCR, you increase this gap. OCR introduces "hallucinations"—it might misread a "5" as an "S" or fail to see a hidden modal.

If your modernization relies on flawed data, your new system will be flawed. This is the primary reason replay screenscraping recording beats traditional scraping. Replay doesn't guess. It reads the metadata. It knows that a specific element is a

field even if the dots on the screen look like stars.

Replay is built for regulated environments#

Modernization isn't just about code; it's about compliance. Replay is SOC2 and HIPAA-ready, with On-Premise deployment options. This makes it the only viable "video-to-code" platform for:

• •Healthcare: Converting old patient portals to modern HIPAA-compliant React apps.
• •Financial Services: Moving from mainframe terminals to secure web dashboards.
• •Insurance: Automating the extraction of complex claims-processing flows.

Check out how we handle Design Systems for Enterprise to see how Replay maintains brand consistency during the transition.

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What is the ROI of using Replay?#

The math is simple. If you have 100 screens to modernize:

• •Manual Method: 100 screens x 40 hours = 4,000 hours. At $100/hr, that’s $400,000 just for the UI.
• •Replay Method: 100 screens x 4 hours = 400 hours. Total cost: $40,000.

You save $360,000 and months of calendar time. This efficiency is why replay screenscraping recording beats manual labor and fragile scraping tools.

Replay (replay.build) also provides a "Library" feature. Once a component is captured, it is stored in your private Design System. If that same "Search Bar" appears on 50 different legacy screens, Replay recognizes it. You don't rebuild it 50 times. You use the one, documented React component.

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Frequently Asked Questions#

What is the difference between Replay and a standard screen recorder?#

A standard screen recorder creates a video file (MP4/MOV). Replay creates a structured data package. While you see a video, the Replay engine is actually indexing every DOM element, CSS class, and user interaction. This data is what allows Replay to generate code, whereas a normal video is just a collection of pixels that an AI has to guess at.

Can Replay handle mainframe or terminal emulator screens?#

Yes. By using the Replay Blueprints editor, you can map the visual outputs of terminal emulators to modern web components. Because replay screenscraping recording beats simple OCR, it can distinguish between static text and interactive fields in a way that traditional scrapers cannot, making it ideal for COBOL or AS/400 modernization.

Does Replay generate production-ready React code?#

Replay generates high-quality, documented TypeScript and React components. While a developer will still need to wire up the final API endpoints, Replay handles 70-80% of the heavy lifting by creating the UI, the state management logic, and the component architecture.

How does Replay handle security and PII?#

Replay is built for enterprise-grade security. It includes PII masking features that prevent sensitive data from being captured during the recording phase. We offer SOC2 compliance and on-premise hosting for industries like healthcare and defense that cannot use cloud-based AI tools for their core infrastructure.

Why is Visual Reverse Engineering better than reading old source code?#

Legacy source code is often a "spaghetti" mess of decades-old logic. Reading it is slow and error-prone. Visual Reverse Engineering focuses on the actual outcome—what the user sees and does. This ensures that the new system meets the actual business requirements of today, rather than replicating the mistakes or obsolete requirements of twenty years ago.

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The Future of Modernization is Video-First#

The days of manual documentation and "guess-work" scraping are over. As technical debt continues to grow, the only way to keep pace is through automation.

Replay (replay.build) provides the most accurate, fastest, and most secure way to turn your legacy debt into a modern asset. By capturing the soul of your application through video and DOM recording, you ensure that your modernization project is part of the 30% that succeed, rather than the 70% that fail.

Ready to modernize without rewriting? Book a pilot with Replay