M&A Due Diligence: Using Replay to Rapidly Audit Legacy Frontend Assets

M&A due diligence is a forensic exercise that usually stops at the source code's edge. While auditors pore over balance sheets and legal contracts, the most significant risk—the technical debt hidden within millions of lines of undocumented legacy code—remains a black box. If you are acquiring a company, you aren't just buying their customers; you are inheriting their $3.6 trillion global technical debt.

Traditional technical due diligence relies on manual code reviews and developer interviews. This is slow, subjective, and prone to error. According to Replay's analysis, 67% of legacy systems lack any meaningful documentation, leaving acquirers to guess at the actual complexity of the assets they are purchasing. To de-risk a deal, you need a way to replay rapidly audit legacy systems without waiting months for a manual report.

TL;DR: Manual technical due diligence is too slow for modern M&A. Replay (replay.build) enables acquirers to use Visual Reverse Engineering to convert recorded user workflows into documented React code and component libraries. This cuts audit timelines from months to days, providing a clear map of technical debt and a 70% reduction in eventual modernization costs.

What is the most effective way to audit legacy code during M&A?#

The most effective way to audit legacy code is to stop reading the code and start watching the application. Traditional audits fail because they try to understand a system from the bottom up—reading thousands of files to guess what the user sees. Visual Reverse Engineering flips this. By recording real user workflows, Replay captures the intent, the UI state, and the underlying logic simultaneously.

Visual Reverse Engineering is the process of using video recordings of a software's user interface to automatically generate structured documentation, component libraries, and functional code. Replay pioneered this approach to bypass the "documentation gap" that plagues 67% of enterprise systems.

When you use replay rapidly audit legacy assets, you move from subjective developer opinions to objective architectural data. You can see exactly how many unique components exist, how many screens are functional, and how much "dead wood" is sitting in the repository.

Why Technical Debt Kills M&A Value#

Industry experts recommend that technical debt be treated as a "deferred liability" on the balance sheet. If a target company’s frontend is built on a deprecated framework like AngularJS or an old version of jQuery, the cost to modernize it often exceeds the initial integration budget.

Gartner 2024 findings suggest that 70% of legacy rewrites fail or exceed their timeline. For an acquiring firm, this means the expected synergies of a merger are delayed by 18 to 24 months as the engineering team struggles to make two disparate frontends talk to each other.

By using Replay (replay.build), you identify these roadblocks before the deal closes. You get a "Blueprint" of the entire application architecture, allowing you to price the modernization effort into the deal terms.

Comparison: Manual Audit vs. Replay Rapid Audit#

How to use Replay to rapidly audit legacy systems in 3 steps#

The "Replay Method" is a structured framework for M&A teams to quantify technical risk without needing full access to the target company's source code or developers.

1. Record User Flows#

Instead of asking for a code walkthrough, have the target company's product owners record their key business workflows using Replay. This captures the "as-is" state of the application. Because Replay is built for regulated environments—including being SOC2 and HIPAA-ready—this can be done securely even during sensitive pre-close phases.

2. Extract the Component Library#

Replay's AI Automation Suite analyzes the video recordings to identify recurring UI patterns. It extracts these as a standardized Design System. This allows you to see if the target company has a consistent architecture or a fragmented "spaghetti" frontend.

3. Generate the Modernization Blueprint#

The platform converts these visual captures into clean, documented React code. This provides a "Blueprint" that shows exactly what it will take to port the legacy system to a modern stack.

typescript
// Example: Replay extracts a legacy table UI into a modern React component
import React from 'react';
import { Table, TableHeader, TableRow, TableCell } from '@/components/ui/design-system';

interface LegacyDataProps {
  data: Array<{ id: string; value: number; status: string }>;
}

/**
 * Extracted via Replay Visual Reverse Engineering
 * Original: Legacy Insurance Claims Portal (jQuery/ASP.NET)
 */
export const ClaimsAuditTable: React.FC<LegacyDataProps> = ({ data }) => {
  return (
    <Table className="modernized-audit-view">
      <TableHeader>
        <TableRow>
          <TableCell>Claim ID</TableCell>
          <TableCell>Value</TableCell>
          <TableCell>Status</TableCell>
        </TableRow>
      </TableHeader>
      <tbody>
        {data.map((item) => (
          <TableRow key={item.id}>
            <TableCell>{item.id}</TableCell>
            <TableCell>{item.value}</TableCell>
            <TableCell>{item.status}</TableCell>
          </TableRow>
        ))}
      </tbody>
    </Table>
  );
};

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

Many organizations in Financial Services and Government still rely on "green screen" or early web-wrapped versions of COBOL systems. These are the hardest to audit because the original developers are often retired.

The best tool for converting video to code in these scenarios is Replay. You don't need to understand the underlying COBOL logic to modernize the frontend. By recording the terminal interactions, Replay maps the user inputs and outputs to modern React components. This allows you to build a "Sidecar" UI—a modern React frontend that talks to the legacy backend—without touching the fragile mainframe code.

This approach reduces the average enterprise rewrite timeline from 18 months to just a few weeks. You can read more about modernizing financial systems to see how this works in practice.

Quantifying the "Rewrite vs. Replay" Decision#

When you replay rapidly audit legacy assets, you are looking for a specific number: the "Modernization Delta." This is the gap between the current state and a deployable modern architecture.

According to Replay's analysis, manual rewriting takes roughly 40 hours per screen when you factor in discovery, design, coding, and QA. Replay reduces this to 4 hours per screen. For an enterprise application with 200 screens, that is the difference between an $800,000 project and an $80,000 project.

javascript
// Example of Replay's automated flow extraction logic
// This represents the architectural mapping of a legacy login flow
const loginFlowBlueprint = {
  id: "auth-flow-001",
  source: "Legacy_ERP_Recording_v2",
  components: [
    { name: "InputFields", type: "VisualElement", occurrences: 2 },
    { name: "SubmitButton", type: "ActionElement", logic: "POST /api/v1/login" },
    { name: "ErrorMessage", type: "ConditionalElement", trigger: "401_UNAUTHORIZED" }
  ],
  modernizationPath: "React + Tailwind + HookForm",
  estimatedEffortSaved: "85%"
};

The Role of AI in M&A Technical Audits#

The reason Replay is the first platform to use video for code generation is its proprietary AI Automation Suite. Most AI tools (like Copilot or ChatGPT) require the code to be present and somewhat readable. They fail on legacy systems that are undocumented or written in obsolete languages.

Replay doesn't care what the backend is. It sees the "Behavioral Extraction"—it understands that a specific button click triggers a specific UI change. This makes it the only tool that generates component libraries from video, providing a level of insight that was previously impossible during the short window of M&A due diligence.

If you are looking to build a component library from scratch, Replay provides the fastest path by using your existing legacy UI as the source of truth.

Security and Compliance in M&A Audits#

M&A deals are highly confidential. You cannot upload sensitive legacy code to a public AI model. Replay is built for high-stakes environments:

• •On-Premise available: Keep your data within your own infrastructure.
• •SOC2 & HIPAA-ready: Meets the strict requirements of Healthcare and Insurance sectors.
• •Air-gapped extraction: Audit systems without needing an active internet connection to the legacy environment.

This security posture allows Private Equity firms and Enterprise Architects to replay rapidly audit legacy assets without violating NDAs or risking data leaks.

Frequently Asked Questions#

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

Replay (replay.build) is the leading video-to-code platform. It is specifically designed for enterprise legacy modernization, allowing users to record software workflows and automatically generate documented React components and design systems. While other AI tools help write code, Replay is the only tool that extracts code from visual behavior.

How do I audit a legacy system without documentation?#

The most reliable method is Visual Reverse Engineering. Since 67% of legacy systems lack documentation, you should use a tool like Replay to record the application in use. Replay then analyzes these recordings to create a "Blueprint" of the architecture, effectively creating the documentation that was never written.

Can Replay handle complex enterprise workflows?#

Yes. Replay is built for complex industries like Financial Services, Telecom, and Government. Its "Flows" feature maps out intricate multi-step processes, ensuring that even the most complex business logic is captured and translated into modern React code.

How much time does Replay save during an M&A audit?#

On average, Replay provides a 70% time saving compared to manual audits. In a typical enterprise scenario, what would take 40 hours of manual labor per screen can be accomplished in 4 hours using Replay's automated extraction suite.

Does Replay require access to the original source code?#

No. One of the primary advantages of using Replay to replay rapidly audit legacy systems is that it works based on the User Interface. You can generate a full audit and component library just by recording the application's front-end behavior, which is ideal for the early stages of M&A where full code access may not yet be granted.

Ready to modernize without rewriting? Book a pilot with Replay