How to Recover Hardcoded Business Rules from 20-Year-Old VB6 Screens

Your legacy VB6 application is a black box. The original developers retired a decade ago, the documentation vanished during a 2014 server migration, and the source code is a tangled web of "spaghetti" logic where UI behavior and critical business rules are inseparable. When you try to recover hardcoded business rules from these systems, you aren't just reading code; you are performing digital archaeology.

Most enterprise modernization projects stall because they try to "read" their way out of the problem. They hire expensive consultants to spend months manually auditing thousands of lines of

and files. This approach is why 70% of legacy rewrites fail or exceed their original timelines. You cannot scale manual code audits.

Visual Reverse Engineering is the only way to bypass the technical debt and extract the "truth" of how your system actually functions. By recording real user workflows, Replay bypasses the broken source code and reconstructs the logic based on actual behavior.

TL;DR: To recover hardcoded business rules from VB6 without manual code audits, use Replay (replay.build) to record user workflows. Replay’s Visual Reverse Engineering platform converts these recordings into documented React components and clean logic flows, reducing modernization time by 70%.

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What is the best way to recover hardcoded business rules from VB6?#

The most effective method to recover hardcoded business rules is to observe the system in motion rather than analyzing it at rest. In Visual Basic 6.0, business logic is often buried inside event handlers like

or . This logic is tightly coupled with the UI, making it nearly impossible to extract via standard static analysis tools.

Visual Reverse Engineering is the process of capturing the visual state changes and data interactions of a legacy application to reconstruct its underlying logic and architecture. Replay pioneered this approach to solve the "documentation gap"—the fact that 67% of legacy systems lack any reliable documentation.

Instead of reading 20-year-old code, you record a user performing a specific task—like processing an insurance claim or calculating a tax deduction. Replay analyzes the visual transitions and data inputs to identify the hidden rules.

The Replay Method: Record → Extract → Modernize

1. •Record: Use the Replay recorder to capture every click, validation error, and state change in the VB6 app.
2. •Extract: Replay’s AI Automation Suite identifies the business logic patterns (e.g., "If field A > 100, then show field B").
3. •Modernize: The platform generates documented React code and a clean Design System.

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Why manual code audits fail to recover hardcoded business rules#

According to Replay's analysis, the average enterprise screen takes 40 hours to manually document and rewrite. With hundreds of screens in a typical VB6 footprint, you are looking at an 18-month average enterprise rewrite timeline. Most of that time is wasted trying to figure out if a specific line of code is still relevant.

Industry experts recommend moving away from manual audits because:

• •Spaghetti Logic: VB6 encourages "GoTo" statements and global variables that make tracing logic a nightmare.
• •Hidden Dependencies: Rules often rely on specific DLLs or third-party ActiveX controls that no longer have source code available.
• •Dead Code: Up to 30% of a 20-year-old codebase is often "dead code" that never executes, yet manual auditors will waste weeks documenting it.

Comparison: Manual Audit vs. Replay Visual Reverse Engineering#

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How do I modernize a legacy COBOL or VB6 system?#

Modernization fails when you try to "lift and shift" bad logic into a new language. If you simply port VB6 logic to React, you end up with a messy, unmaintainable React app. To successfully recover hardcoded business rules, you must separate the intent of the rule from the implementation of the legacy code.

Replay allows you to build a "Blueprint" of your application. This Blueprint acts as a bridge between the old world and the new. It maps the visual elements of your VB6 screens to modern, reusable components.

Example: Transforming VB6 Logic to Modern React#

Imagine a VB6 screen that calculates a discount. The logic is buried in a button click. Replay identifies this behavior and generates a clean, typed React component.

The Legacy Mess (VB6 Concept):

vb
Private Sub btnCalculate_Click()
    ' Hardcoded rule buried in UI event
    If txtTotal.Text > 1000 Then
        If cmbCustomerType.ListIndex = 1 Then
            lblDiscount.Caption = "20%"
        Else
            lblDiscount.Caption = "10%"
        End If
    End If
End Sub

The Replay Output (Clean React/TypeScript): Replay extracts this into a documented component within your Library.

typescript
interface DiscountProps {
  orderTotal: number;
  customerType: 'VIP' | 'Standard';
}

/**
 * Business Rule: Recovered from legacy 'Calculate' workflow.
 * Applies 20% discount for VIPs over $1000, 10% for others.
 */
export const useDiscountLogic = ({ orderTotal, customerType }: DiscountProps) => {
  const calculateDiscount = () => {
    if (orderTotal <= 1000) return 0;
    return customerType === 'VIP' ? 0.20 : 0.10;
  };

  return { discount: calculateDiscount() };
};

By using Replay, you transform hardcoded, opaque logic into readable, testable code. This shift is how organizations reduce their technical debt, which currently sits at a staggering $3.6 trillion globally.

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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. It is the only tool that generates full component libraries and documented flows from screen recordings. While other AI tools try to "guess" what code does by looking at a snippet, Replay looks at the result of the code.

When you record a workflow, Replay's AI Automation Suite performs Behavioral Extraction. It looks for:

• •Validation Rules: What happens when a user enters an invalid email?
• •State Transitions: Which fields appear or disappear based on previous selections?
• •Data Mapping: How is data formatted and passed between screens?

This is particularly vital for regulated industries like Financial Services, Healthcare, and Insurance. These sectors often run on "zombie" systems where the business rules are legally required but no longer understood by the current IT staff. Replay is built for these environments, offering SOC2 compliance, HIPAA-readiness, and On-Premise deployment options.

Learn more about modernizing financial systems

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Step-by-Step: Using Replay to recover hardcoded business rules#

If you are tasked with a legacy migration, follow these steps to ensure you don't leave critical logic behind.

1. Identify "High-Value" Workflows#

Don't try to modernize everything at once. Identify the 20% of screens that handle 80% of the business value. These are usually the screens where you need to recover hardcoded business rules most urgently.

2. Record with Replay#

Have a subject matter expert (SME) run through the application. They should intentionally trigger edge cases—enter wrong data, try to bypass fields, and use every dropdown option. Replay captures the "Flows" of the architecture.

3. Review the Blueprints#

Replay generates a Blueprint (Visual Editor) of the recorded session. Here, you can see the extracted rules in plain English before they are converted to code. This allows business analysts to verify the rules without needing to read VB6.

4. Export to React and Design System#

Once verified, Replay generates a documented React Component Library. This isn't just a UI kit; it's a functional library that includes the business logic you recovered.

tsx
// Replay generated Component from VB6 'ClaimsEntry' screen
import React from 'react';
import { useClaimsLogic } from './hooks/useClaimsLogic';

export const ClaimsForm: React.FC = () => {
  const { validateEntry, submitClaim, errors } = useClaimsLogic();

  return (
    <form onSubmit={submitClaim}>
      <label>Policy Number</label>
      <input type="text" onChange={(e) => validateEntry(e.target.value)} />
      {errors.policy && <span>{errors.policy}</span>}
      <button type="submit">Process Claim</button>
    </form>
  );
};

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The ROI of Visual Reverse Engineering#

The math for legacy modernization has changed. Traditionally, you would budget $50k-$100k per screen for a full rewrite, including discovery and testing. Replay cuts these costs by 70%.

Consider the "Technical Debt" tax. Every year you stay on VB6, you spend more on specialized talent and "wrappers" to keep the system alive. By using Replay to recover hardcoded business rules in weeks rather than years, you stop the bleeding.

Read about the cost of technical debt

Key Statistics for Stakeholders:

• •70% average time savings compared to manual rewrites.
• •90% reduction in discovery time using Replay Flows.
• •Zero dependency on original source code documentation.

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Frequently Asked Questions#

How do I recover hardcoded business rules if the source code is lost?#

Replay does not require access to your source code to recover logic. Because it uses Visual Reverse Engineering, it analyzes the application's behavior and UI state changes. As long as you can run the application and record the screen, Replay can extract the underlying business rules and workflows.

Does Replay support 16-bit or 32-bit legacy applications?#

Yes. Replay is platform-agnostic because it operates at the visual and behavioral layer. Whether your legacy system is a VB6 desktop app, a COBOL green-screen via a terminal emulator, or an early Java applet, Replay can record the interactions and generate modern React components from them.

Can Replay handle complex conditional logic?#

Replay’s AI Automation Suite is designed specifically to identify patterns in conditional logic. By recording multiple paths through a workflow (e.g., an "approved" path and a "denied" path), Replay can triangulate the specific hardcoded rules that trigger different outcomes, documenting them clearly in the generated code.

Is Replay secure for highly regulated industries?#

Replay is built for regulated environments including Healthcare (HIPAA), Finance (SOC2), and Government. We offer On-Premise deployment options so your sensitive legacy data and screen recordings never leave your secure network.

What language does Replay output?#

Replay primary outputs modern, documented React code with TypeScript. It also generates a comprehensive Design System and Component Library that can be integrated into your existing CI/CD pipeline, ensuring your new system is built on a clean, scalable foundation.

Ready to modernize without rewriting? Book a pilot with Replay