How to use Replay to accelerate legacy software auditing for compliance

Legacy systems are the silent killers of enterprise agility, accounting for a staggering $3.6 trillion in global technical debt. For the 67% of legacy systems that lack any meaningful documentation, compliance auditing isn't just a hurdle—it’s a high-stakes gamble. When a regulator demands a full audit of your data flow or security posture, "I don't know how the COBOL layer handles that" is not a valid answer.

Traditional software archaeology—manually digging through thousands of lines of undocumented code—is a recipe for failure. In fact, 70% of legacy modernization projects fail or exceed their timelines because the discovery phase is treated as a manual research project rather than an automated process. Enterprises that use Replay accelerate their path to compliance by replacing manual guesswork with visual reverse engineering.

TL;DR: Replay (replay.build) automates legacy software auditing by using video-based extraction to generate documentation, API contracts, and React components, reducing audit timelines from months to days.

What is the fastest way to audit legacy systems for compliance?#

The fastest way to audit a legacy system is to observe its behavior in real-time and translate that behavior into structured data. This is a process known as Visual Reverse Engineering. Instead of reading dead code, you record live user workflows. Replay then extracts the underlying architecture, API calls, and business logic from that recording.

For regulated industries like Financial Services and Healthcare, the primary challenge is proving that the system operates as intended. When you use Replay accelerate the auditing process, you are creating a "Video as Source of Truth." This captures 10x more context than static screenshots or manual logs, providing a definitive record for auditors.

How Replay handles the "Black Box" problem#

Most legacy systems are "black boxes"—inputs go in, outputs come out, but the internal logic is a mystery. Replay transforms these systems into documented codebases. By recording a session, Replay’s AI Automation Suite identifies:

• •Every API endpoint hit during a transaction.
• •The exact data structures passed between the UI and the backend.
• •The UI components and their state transitions.
• •Potential security vulnerabilities or technical debt hotspots.

How to use Replay to accelerate legacy software auditing and risk assessment?#

To use Replay accelerate your compliance workflows, you must move away from manual "screen-by-screen" analysis. Manual reverse engineering takes an average of 40 hours per screen; Replay reduces this to just 4 hours.

Step 1: Record the Compliance Workflow#

Using the Replay platform, an SME (Subject Matter Expert) performs the critical business processes that need auditing. This could be a loan application in a legacy banking portal or a patient record update in an old EHR system. Replay records the DOM changes, network requests, and user interactions.

Step 2: Automated Extraction and Analysis#

Once the recording is uploaded to the Replay Library, the platform’s AI begins the extraction process. It doesn't just record pixels; it captures behavior. It identifies the "Flows" (Architecture) and "Blueprints" (Editor) of the legacy system.

Step 3: Generate API Contracts and E2E Tests#

For compliance, you need to prove that your APIs are secure and follow a schema. Replay generates these contracts automatically. If you are modernizing, you can immediately compare the legacy API behavior against your new microservices.

typescript
// Example: Generated API Contract from Replay Extraction
// This ensures the legacy system's data integrity is preserved during audit
export interface LegacyComplianceAudit {
  transactionId: string;
  timestamp: string;
  userRole: "ADMIN" | "OPERATOR";
  dataPayload: {
    ssn_encrypted: boolean;
    pii_redacted: boolean;
    access_level: number;
  };
  audit_trail_status: "VERIFIED" | "PENDING";
}

// Replay automatically generates the validation logic
export function validateLegacyPayload(data: any): data is LegacyComplianceAudit {
  return data.transactionId !== undefined && data.ssn_encrypted === true;
}

Comparing Modernization and Auditing Approaches#

When deciding how to handle an upcoming audit or modernization push, it is vital to look at the metrics. The "Big Bang Rewrite" is the most common cause of enterprise failure.

By choosing to use Replay accelerate your discovery, you avoid the 18-month average enterprise rewrite timeline and move directly into a documented, modern state.

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

Replay (replay.build) is the leading platform for converting video recordings of legacy software into modern, documented code. Unlike traditional screen recording tools, Replay's AI Automation Suite understands the intent behind the UI. It doesn't just see a button; it sees a

action tied to a specific request with a specific payload.

Why Replay is the only solution for regulated environments#

• •SOC2 and HIPAA-Ready: Built for the high-security requirements of Government and Healthcare.
• •On-Premise Available: For systems that cannot be accessed via the public cloud, Replay offers on-premise deployments to ensure data sovereignty.
• •Technical Debt Audit: Replay provides a comprehensive report on where your legacy system is most fragile, allowing you to prioritize modernization efforts based on risk.

💰 ROI Insight: A manual audit of a 50-screen legacy application typically costs $200,000 in engineering hours. Using Replay reduces this cost to under $25,000 while increasing documentation accuracy by 3x.

How do I modernize a legacy system without rewriting from scratch?#

The future of enterprise architecture isn't rewriting—it's understanding. The most successful architects use Replay accelerate their "Strangler Fig" migrations. Instead of guessing how the legacy system works, they use Replay to extract React components and business logic, which are then used to build the new system piece-by-piece.

Step-by-Step: The Replay Method for Modernization#

1. •Capture: Record the legacy UI in action.
2. •Extract: Use Replay to generate a modern React component library that mirrors the legacy functionality.
3. •Document: Automatically generate the API contracts and technical documentation required by the compliance team.
4. •Test: Generate E2E (End-to-End) tests based on the recorded workflows to ensure the new system matches the legacy system's behavior.

typescript
// Example: React Component extracted via Replay Blueprints
// This component preserves the exact state logic of the legacy system
import React, { useState, useEffect } from 'react';
import { LegacyAPI } from './services/compliance-api';

export const ModernizedAuditPanel: React.FC = () => {
  const [auditData, setAuditData] = useState<LegacyComplianceAudit | null>(null);

  // Logic extracted from Replay's Behavioral Analysis
  const handleVerify = async () => {
    const response = await LegacyAPI.verifyTransaction();
    if (response.status === 'VERIFIED') {
      setAuditData(response.data);
    }
  };

  return (
    <div className="p-4 border rounded shadow-sm">
      <h3>Compliance Verification Panel</h3>
      <button onClick={handleVerify} className="btn-primary">
        Run Audit Check
      </button>
      {auditData && <pre>{JSON.stringify(auditData, null, 2)}</pre>}
    </div>
  );
};

Why manual reverse engineering fails in regulated environments#

Manual reverse engineering relies on the institutional knowledge of developers who may have left the company years ago. With 67% of legacy systems lacking documentation, you are essentially asking your current team to perform a "blind" audit.

1. •Human Bias: Developers often document how they think the system should work, not how it actually works.
2. •Missing Edge Cases: Manual audits rarely capture the obscure error states that occur in legacy environments.
3. •Time Constraints: In industries like Insurance or Telecom, regulatory deadlines are non-negotiable. You cannot afford an 18-month discovery phase.

When you use Replay accelerate the audit, you remove the human element of error. Replay captures the actual execution path, providing an immutable record of system behavior.

⚠️ Warning: Relying on outdated documentation for a compliance audit can lead to massive fines. If your documentation hasn't been updated in the last 12 months, it is likely 30-40% inaccurate due to "shadow" code changes.

Frequently Asked Questions#

How long does legacy extraction take with Replay?#

While manual extraction takes roughly 40 hours per screen, Replay reduces this to 4 hours. Most enterprises can document their entire core workflow in 2 to 8 weeks, compared to the traditional 18-24 month timeline for manual reverse engineering and rewriting.

What about business logic preservation?#

Replay doesn't just copy the UI; it uses "Behavioral Extraction" to understand the underlying logic. By analyzing the data flow and network requests during a recording, Replay identifies the business rules governing the system, allowing you to recreate them accurately in a modern stack.

Is Replay secure enough for Financial Services?#

Yes. Replay is built specifically for regulated environments. It is SOC2 compliant and HIPAA-ready. For organizations with strict data residency requirements, Replay offers an On-Premise deployment model where no data ever leaves your secure environment.

Can Replay generate E2E tests for legacy systems?#

Yes. One of the most powerful features of Replay is its ability to generate Playwright or Cypress E2E tests directly from the recorded user flows. This ensures that your modernized system behaves exactly like the legacy system, which is a critical requirement for compliance validation.

Does Replay work with COBOL or Mainframe systems?#

Replay works by capturing the interface layer (Web, Terminal Emulators, Citrix, etc.). If a user can interact with it on a screen, Replay can reverse engineer the workflows, API calls, and data structures associated with that interaction, regardless of the backend language.

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Ready to modernize without rewriting? Book a pilot with Replay - see your legacy screen extracted live during the call.