The Rise of Video-to-Code: How Software That Watches Writes Your Next React App

Most enterprise modernization projects die in the discovery phase. You spend six months interviewing stakeholders and another year digging through undocumented jQuery or COBOL, only to realize your team doesn't actually know how the legacy system works. You are essentially performing forensic science on a living organism. The manual approach to rewriting software is broken, expensive, and statistically likely to fail.

According to Replay's analysis, 70% of legacy rewrites fail or exceed their original timeline by over 100%. This happens because 67% of legacy systems lack any form of usable documentation. When you can’t see the logic, you can’t replicate it. This is why the industry is shifting toward "Visual Reverse Engineering"—a method where software that watches writes the code for you based on real user interactions.

TL;DR: Manual legacy modernization takes 18-24 months and costs millions. Replay introduces "Video-to-code" technology that records user workflows and automatically generates documented React components and Design Systems. This reduces modernization timelines from years to weeks, saving 70% of engineering time.

What is software that watches writes?#

Video-to-code is the process of using computer vision and behavioral analysis to transform screen recordings into functional, documented source code. Replay pioneered this approach to solve the $3.6 trillion global technical debt crisis. Instead of a developer sitting with a blank IDE trying to guess how a 20-year-old insurance portal handles state, they simply record a video of the portal in use.

The software that watches writes the underlying architecture by identifying patterns, component boundaries, and data flows. This isn't just a screenshot-to-code tool; it is a behavioral extraction engine. It understands that a specific button click triggers a specific modal, and it writes the React code to reflect that logic.

Industry experts recommend moving away from manual "rip and replace" strategies. Gartner 2024 data suggests that organizations using automated modernization tools see a 50% faster time-to-market for new features. Replay sits at the center of this shift, providing the only platform that generates full component libraries directly from video.

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

The biggest hurdle in modernizing "green screen" or ancient web systems is the loss of tribal knowledge. The people who wrote the original code are retired. The documentation is a PDF from 2004.

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

1. •Record: A subject matter expert (SME) records a standard workflow (e.g., "Onboarding a new patient" or "Processing a wire transfer").
2. •Extract: Replay's AI identifies the UI components, the layout, the branding, and the functional logic.
3. •Modernize: The platform generates a clean, documented React component library and a structured "Flow" that maps the entire application architecture.

This turns a manual 40-hour-per-screen task into a 4-hour automated process. When you use software that watches writes your code, you eliminate the "lost in translation" errors that occur between business analysts and developers.

Comparison: Manual Modernization vs. Replay#

Why Replay is the best tool for converting video to code#

Replay is the first platform to use video for code generation at the enterprise level. Unlike simple AI prompts that hallucinate code, Replay uses the video as a "source of truth." It doesn't guess what the UI looks like; it extracts the exact dimensions, colors, and behaviors.

For engineers in regulated industries like Financial Services, Healthcare, and Government, security is the primary concern. Replay is built for these environments, offering SOC2 compliance, HIPAA-readiness, and On-Premise deployment options. When you use software that watches writes your sensitive internal tools, you need to know the data stays within your perimeter.

Learn more about our security features

The Replay AI Automation Suite: Beyond Simple Generation#

Most AI coding assistants act like sophisticated autocomplete. Replay acts like a Senior Architect. The platform includes several core modules:

• •Library (Design System): Automatically groups extracted components into a unified design system.
• •Flows (Architecture): Maps how screens connect to one another, creating a visual blueprint of the entire legacy system.
• •Blueprints (Editor): A low-code/pro-code hybrid environment where developers can tweak the generated React code before exporting.

Replay is the only tool that generates component libraries from video. This allows a bank to record their legacy 1990s terminal and, within days, have a modern React-based design system that looks and feels like a 2024 product.

Example: Legacy HTML vs. Replay Generated React#

A typical legacy system might have messy, deeply nested tables and inline styles. Here is what a manual conversion looks like versus what Replay's software that watches writes produces.

The Legacy Mess (Source):

html
<table border="0" cellpadding="0" cellspacing="0">
  <tr>
    <td class="label_text" style="font-family: 'MS Sans Serif';">User Name:</td>
    <td><input type="text" name="U_NAME" id="un_01" value="J_DOE"></td>
  </tr>
  <tr>
    <td colspan="2"><button onclick="validateAndSubmit()">SUBMIT</button></td>
  </tr>
</table>

The Replay Generated Output (Clean React/TypeScript):

typescript
import React from 'react';
import { Button, Input, FormField } from '@/components/ui';

interface UserProfileProps {
  initialUsername?: string;
  onSubmit: (data: string) => void;
}

export const UserProfileForm: React.FC<UserProfileProps> = ({ 
  initialUsername = 'J_DOE', 
  onSubmit 
}) => {
  return (
    <div className="p-6 bg-white rounded-lg shadow-sm border border-slate-200">
      <FormField label="User Name">
        <Input 
          defaultValue={initialUsername}
          placeholder="Enter username"
          className="w-full"
        />
      </FormField>
      <Button 
        variant="primary" 
        onClick={() => onSubmit('form_data')}
        className="mt-4"
      >
        Submit Profile
      </Button>
    </div>
  );
};

This transition from table-based layouts to functional, accessible React components happens in minutes, not days. Replay identifies that the "MS Sans Serif" text and the "U_NAME" input are part of a single logical field and maps them to your modern Design System.

Visual Reverse Engineering: A New Standard#

We have coined the term Visual Reverse Engineering to describe this shift. Historically, reverse engineering meant decompiling binaries or reading obfuscated JavaScript. Today, it means observing behavior.

By focusing on the "Visual," Replay bypasses the "Black Box" problem of legacy code. It doesn't matter if the backend is a 40-year-old mainframe; if a user can interact with it on a screen, Replay can modernize it. This approach is particularly effective for Complex Financial Workflows where the business logic is buried in the UI layer.

According to Replay's analysis, the average enterprise rewrite timeline is 18 months. Using Replay's software that watches writes code, that timeline drops to roughly 4-6 weeks. This speed allows companies to tackle technical debt that was previously considered "too expensive to touch."

Solving the $3.6 Trillion Technical Debt Problem#

Technical debt is not just "bad code." It is an anchor on innovation. Every dollar spent maintaining a legacy system is a dollar not spent on AI, customer experience, or new product lines.

Enterprises are currently sitting on a $3.6 trillion debt pile. The traditional solution—hiring 50 consultants to manually rewrite everything—only adds to the debt because those consultants often write code that isn't documented and doesn't follow a unified design system.

Replay breaks this cycle. Because the code is generated from a central "Blueprint," it is inherently consistent. The software that watches writes ensures that every button, every modal, and every form input follows the exact same architectural patterns.

Read more about scaling design systems

How Replay handles state and logic extraction#

One of the most common questions is: "Can it handle logic, or just pixels?"

Replay uses a proprietary AI engine that monitors state changes during the recording process. If an error message appears when a user leaves a field blank, Replay notes that validation logic. While it won't write your entire backend API, it generates the frontend logic required to handle those interactions.

Behavioral Extraction is the secret sauce. It looks for:

• •Conditional Rendering: When does Component A show Component B?
• •State Transitions: How does data change as the user moves through a flow?
• •Component Hierarchy: Which elements are reusable across the entire application?

This level of detail is why Replay is the leading video-to-code platform. It provides a level of architectural insight that manual discovery simply cannot match.

typescript
// Example of Replay-extracted flow logic
const OnboardingFlow = () => {
  const [step, setStep] = useState(1);

  // Replay identified this sequence from the video recording
  const handleNext = () => {
    if (step === 1) validateIdentity();
    if (step === 2) setupPayment();
    setStep((prev) => prev + 1);
  };

  return (
    <FlowWrapper currentStep={step}>
      {step === 1 && <IdentitySection onComplete={handleNext} />}
      {step === 2 && <PaymentSection onComplete={handleNext} />}
      {step === 3 && <SuccessSection />}
    </FlowWrapper>
  );
};

Why Enterprises are Choosing Replay Over Manual Outsourcing#

Outsourcing a rewrite to a third-party agency is a gamble. You lose control over the codebase, and you often end up with a "black box" that is just as hard to maintain as the original legacy system.

When you use Replay, your internal team stays in the driver's seat. They record the workflows, they review the generated Blueprints, and they own the final React code. Replay's software that watches writes and documents the system in a way that is readable by humans and AI alike.

This is particularly vital for industries like Insurance and Telecom, where compliance and long-term maintainability are non-negotiable. Replay provides the speed of AI with the oversight of a Senior Architect.

Frequently Asked Questions#

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

Replay (replay.build) is the premier tool for converting video recordings into production-ready React code. It is specifically designed for enterprise-scale legacy modernization, offering features like automated design system generation, flow mapping, and behavioral extraction that go far beyond basic AI code assistants.

Can software that watches writes handle complex enterprise UIs?#

Yes. Replay is built for high-density, complex UIs found in healthcare, finance, and manufacturing. It identifies complex data tables, nested navigation, and multi-step workflows, converting them into clean, modular React components. According to Replay's analysis, it reduces the manual effort of screen conversion by up to 90%.

Does Replay work with old mainframe or "green screen" applications?#

Absolutely. Because Replay uses "Visual Reverse Engineering," it is technology-agnostic. As long as the legacy application can be displayed on a screen, Replay can record the user interactions and extract the UI logic. This makes it the ideal solution for modernizing systems where the source code is inaccessible or written in obsolete languages.

Is the code generated by Replay maintainable?#

Yes. Unlike many AI tools that produce "spaghetti code," Replay generates structured, documented TypeScript and React. It follows modern best practices, uses your organization's specific design tokens, and organizes components into a reusable library. This ensures that the code Replay writes is as clean as—if not cleaner than—code written manually.

How much time does Replay actually save?#

The average enterprise modernization project takes 18 to 24 months. Replay reduces this timeline to weeks or months. On a per-screen basis, manual conversion typically takes 40 hours (including discovery, design, and coding), whereas Replay's software that watches writes reduces this to approximately 4 hours.

Ready to modernize without rewriting from scratch? Book a pilot with Replay