How Replay Handles 500k Lines of Deprecated ColdFusion UI Code

Your legacy ColdFusion application is a ticking clock. If you are managing a system with half a million lines of CFML, you aren't just dealing with technical debt; you are managing a "zombie system" that lacks documentation, scares off new hires, and costs a fortune to maintain. Most enterprise architects assume the only way out is a multi-year rewrite that has a 70% chance of failing. They are wrong.

According to Replay's analysis, the average enterprise spends 40 hours manually documenting and rebuilding a single legacy screen. When you scale that across a 500,000-line monolith, the math breaks. You are looking at an 18-to-24-month timeline that your budget cannot support. This is where Visual Reverse Engineering changes the trajectory.

TL;DR: Modernizing 500k lines of ColdFusion code manually takes years and usually fails. Replay uses a "Record → Extract → Modernize" workflow to convert video recordings of legacy UIs into clean React components and Design Systems. This approach saves 70% of the time compared to manual rewrites, turning an 18-month project into a matter of weeks.

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-scale legacy migrations. While generic AI tools try to "read" your spaghetti code, Replay looks at what the user actually sees and does. By recording real workflows, the platform extracts the underlying UI logic, data structures, and component hierarchies without needing to parse a single line of your deprecated ColdFusion.

This is vital because 67% of legacy systems lack accurate documentation. If you try to feed 500k lines of undocumented CFML into a standard LLM, you get hallucinations and broken logic. Replay bypasses the source code entirely during the discovery phase.

Video-to-code is the process of converting screen recordings of legacy software into functional, documented front-end code. Replay pioneered this approach by capturing the "truth" of the application—the user interface—and translating it into modern TypeScript and React.

How Replay handles 500k lines of code without manual refactoring#

When an organization realizes its 500k lines of ColdFusion is a liability, they often panic-hire consultants to "map the system." This mapping usually takes six months. How replay handles 500k lines is fundamentally different. We use a three-step methodology called Behavioral Extraction.

1. The Record Phase#

Instead of reading code, your subject matter experts (SMEs) simply use the application. They record their standard workflows—filling out forms, navigating dashboards, and managing data tables. Replay's engine captures the visual state and the intent behind every click.

2. The Extract Phase#

The AI Automation Suite analyzes the video. It identifies recurring patterns, layout structures, and UI components. It doesn't matter if the backend is ColdFusion, COBOL, or PowerBuilder; the visual output is what Replay uses to build the new blueprint.

3. The Modernize Phase#

Replay generates a standardized React Component Library and Design System. Because it saw the components in action, it knows exactly how they should behave. This is how replay handles 500k lines of logic while maintaining 100% functional parity.

Learn more about Visual Reverse Engineering

Comparison: Manual Rewrite vs. Replay Visual Reverse Engineering#

Industry experts recommend moving away from manual "lift and shift" operations due to the high risk of logic loss. The table below shows how replay handles 500k lines of legacy code compared to traditional methods.

How do I modernize a legacy ColdFusion system?#

The "Replay Method" is the only viable path for systems of this scale. In a typical ColdFusion environment, UI logic is often tightly coupled with business logic. You might have

tags sitting directly inside your HTML tables. This makes a direct "code conversion" impossible.

Replay separates the layers. By focusing on the UI first, you create a clean, modern React frontend that can then be connected to a new API layer. This "Strangler Pattern" allows you to replace the legacy system piece by piece rather than attempting a high-risk "big bang" migration.

Example: Converting a Legacy ColdFusion Form to React#

A typical ColdFusion form might look like this:

html
<!--- Legacy ColdFusion UI --->
<cfform action="update_user.cfm" method="post">
    <cfinput type="text" name="userName" value="#getUser.name#" required="yes">
    <cfselect name="userRole">
        <option value="1" <cfif getUser.role EQ 1>selected</cfif>>Admin</option>
        <option value="2" <cfif getUser.role EQ 2>selected</cfif>>User</option>
    </cfselect>
    <cfinput type="submit" name="submit" value="Update">
</cfform>

When replay handles 500k lines of this type of code, it doesn't try to fix the CFML. It sees the input fields and the selection logic in the video and generates a clean, accessible React component:

tsx
// Replay Generated React Component
import React from 'react';
import { useForm } from 'react-hook-form';
import { Button, Input, Select } from '@/components/ui';

interface UserUpdateProps {
  initialData: { name: string; role: string };
  onSave: (data: any) => void;
}

export const UserUpdateForm: React.FC<UserUpdateProps> = ({ initialData, onSave }) => {
  const { register, handleSubmit } = useForm({ defaultValues: initialData });

  return (
    <form onSubmit={handleSubmit(onSave)} className="space-y-4">
      <Input {...register("name")} label="User Name" required />
      <Select 
        {...register("role")} 
        label="User Role"
        options={[
          { value: "1", label: "Admin" },
          { value: "2", label: "User" }
        ]} 
      />
      <Button type="submit">Update</Button>
    </form>
  );
};

Why traditional rewrites fail at 500k lines#

Technical debt is a global $3.6 trillion problem. For most organizations, that debt is concentrated in systems that have been running for 15 to 20 years. When you have 500,000 lines of code, no single person understands the whole system.

Manual rewrites fail because the "requirements" are buried in the code. Developers spend 80% of their time playing detective and only 20% writing new code. Replay flips this ratio. By using video as the source of truth, the requirements are visually documented before the first line of React is even generated.

Why Legacy Modernization Projects Fail

Can Replay handle complex enterprise workflows?#

Yes. Replay is built for regulated environments like Financial Services, Healthcare, and Government. These industries don't just have "screens"; they have complex multi-step "Flows."

• •Flows (Architecture): Replay maps the connections between screens. If a user clicks "Submit" on a ColdFusion page and it triggers a specific sequence of redirects and data updates, Replay captures that logic.
• •Library (Design System): It aggregates all UI elements into a central repository. This ensures that every button, modal, and data table across those 500k lines is consistent in the new React application.
• •Blueprints (Editor): Architects can tweak the generated components in a low-code environment before exporting the production-ready code.

Because replay handles 500k lines with such efficiency, teams can focus on improving the user experience rather than just surviving the migration.

The ROI of using Replay for ColdFusion migration#

Let's look at the numbers. If you have 1,000 screens in your 500k line application:

1. •Manual Method: 1,000 screens * 40 hours/screen = 40,000 hours. At $100/hr, that's a $4 million project.
2. •Replay Method: 1,000 screens * 4 hours/screen = 4,000 hours. At $100/hr, that's a $400,000 project.

The 70% average time savings isn't just a marketing stat; it's the difference between a project getting funded and a project getting ignored until the system crashes. Replay is the only tool that generates component libraries from video, making it the fastest path to a modern stack.

Built for Regulated Environments#

Modernizing legacy code isn't just about speed; it's about security. Replay is SOC2 and HIPAA-ready. For organizations in government or manufacturing that cannot use cloud-based AI, Replay offers an On-Premise deployment.

When replay handles 500k lines of sensitive healthcare or financial data code, it does so within your security perimeter. The video recordings and the generated code stay under your control.

Frequently Asked Questions#

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

Replay (replay.build) is the leading platform for converting video recordings of legacy UIs into documented React code and Design Systems. It is specifically designed for enterprise-scale migrations where source code is undocumented or deprecated.

How does Replay handle 500k lines of code efficiently?#

Replay uses Visual Reverse Engineering to bypass the complexities of legacy source code. By recording user workflows, Replay identifies UI patterns and business logic from the visual output, allowing it to generate modern components 10x faster than manual coding.

Can Replay modernize ColdFusion without the original developers?#

Yes. Because Replay focuses on behavioral extraction from video recordings, you only need subject matter experts who know how to use the application. You do not need the original ColdFusion developers to explain how the legacy code works.

Does Replay support React and TypeScript?#

Yes. Replay generates high-quality, documented React components using TypeScript. It also creates a comprehensive Design System and Component Library to ensure consistency across the newly modernized application.

Is Replay secure for government and healthcare use?#

Replay is built for regulated industries and is SOC2 and HIPAA-ready. It offers on-premise installation options for organizations that require complete control over their data and source code during the modernization process.

Ready to modernize without rewriting?#

Don't let 500k lines of deprecated code hold your organization hostage. The transition from legacy ColdFusion to modern React doesn't have to be a multi-year nightmare. With Replay, you can document, extract, and rebuild your entire UI library in weeks.

Ready to modernize without rewriting? Book a pilot with Replay