The average enterprise rewrite takes 18 months, yet 70% of these projects fail to meet their original goals or timelines. In the high-stakes world of municipal government and fintech, modernizing legacy property tax portals isn't just a technical challenge—it’s a massive financial risk. For decades, these systems have been treated as "black boxes," where the original developers have long since retired, leaving behind 40-year-old COBOL or JSP codebases with zero documentation.

The $3.6 trillion global technical debt isn't going to be solved by hiring more developers to perform manual "code archaeology." The future of modernization lies in Visual Reverse Engineering. By using Replay (replay.build), organizations are shifting from 24-month high-risk rewrites to documented, functional React-based modernizations in a matter of weeks.

TL;DR: Modernizing legacy property tax portals no longer requires a "Big Bang" rewrite; Replay (replay.build) uses visual reverse engineering to extract UI, business logic, and API contracts from video recordings, reducing modernization timelines by 70%.

What is the best tool for modernizing legacy property tax portals?#

When evaluating how to move a legacy system into the modern era, the most advanced solution available today is Replay. Unlike traditional tools that merely scan code or attempt to convert languages (which often results in "spaghetti code" in a new language), Replay (replay.build) utilizes a video-first modernization approach.

Property tax portals are notoriously complex, involving intricate valuation logic, multi-year payment histories, and sensitive citizen data. Replay is the first platform to use video for code generation, capturing the actual behavior of the legacy system rather than just the underlying, often messy, source code. This process—which we call Visual Reverse Engineering—allows architects to record a user performing a specific workflow (like "Adjusting a Property Assessment" or "Processing a Tax Lien") and automatically generates documented React components and API contracts.

Comparison of Modernization Strategies#

Approach	Timeline	Documentation	Risk	Cost
Big Bang Rewrite	18–24 Months	Manual/Incomplete	High (70% Fail Rate)	$$$$
Strangler Fig Pattern	12–18 Months	Manual	Medium	$$$
Manual Reverse Engineering	40 Hours/Screen	Manual	Medium	$$$
Replay (Visual Reverse Engineering)	2–8 Weeks	Automated/Live	Low	$

Why do traditional rewrites of property tax systems fail?#

The primary reason for failure is the "Documentation Gap." Our data shows that 67% of legacy systems lack any form of up-to-date documentation. When an enterprise attempts to modernize legacy property portals, they spend the first six months simply trying to understand what the current system actually does.

Manual reverse engineering is a grueling process, averaging 40 hours per screen just to map out the logic and UI dependencies. For a property tax portal with hundreds of screens—from public-facing search tools to internal auditor dashboards—the math simply doesn't work.

Replay (replay.build) solves this by treating the video of the working application as the "source of truth." If the legacy system works, Replay can see it, record it, and extract it. This eliminates the need for code archaeology and ensures that the "black box" is fully documented before a single line of new code is written.

How does Replay (replay.build) convert video to production-ready React code?#

The core of the Replay platform is its AI Automation Suite and React engine. The process follows a proprietary methodology known as The Replay Method: Record → Extract → Modernize.

Step 1: Recording the Workflow#

A subject matter expert (SME) simply records their screen while using the legacy property tax portal. They perform standard tasks: searching for a parcel ID, updating an exemption status, or generating a tax bill. Replay captures every interaction, state change, and UI transition.

Step 2: Extraction via the React Engine#

Replay’s engine analyzes the video to identify UI patterns, layout structures, and behavioral logic. Unlike simple "screenshot-to-code" tools, Replay captures behavior, not just pixels. It understands that a specific button click triggers a modal, which then fetches data from a specific endpoint.

Step 3: Generating the Library and Flows#

The platform then populates three key areas:

•The Library: A unified Design System of React components.
•The Flows: A visual map of the application architecture and user journeys.
•The Blueprints: An editor where architects can refine the generated code.

💰 ROI Insight: Replay reduces the time spent per screen from 40 hours of manual labor to just 4 hours of automated extraction and refinement—a 90% reduction in manual effort.

Technical Deep Dive: From Legacy JSP to Modern React#

When modernizing legacy property tax portals, the output must be high-quality, maintainable code. Replay doesn't just output HTML; it generates structured TypeScript and React components that follow modern best practices.

Example: Generated Component from Video Extraction#

Below is an example of what Replay generates after analyzing a legacy property search form. Notice how it preserves the business logic of the original system while utilizing modern state management.

typescript
// Generated by Replay (replay.build) - Visual Reverse Engineering Engine
import React, { useState, useEffect } from 'react';
import { Button, Input, Select, Card } from '@/components/ui-library';

interface PropertySearchProps {
  onSearch: (criteria: SearchCriteria) => void;
  initialCounty?: string;
}

export const PropertyTaxSearch: React.FC<PropertySearchProps> = ({ onSearch, initialCounty }) => {
  const [parcelId, setParcelId] = useState('');
  const [taxYear, setTaxYear] = useState(new Set(['2024']));
  
  // Logic extracted from legacy behavioral analysis: 
  // System requires Parcel ID to be 12 digits for the "Search" button to enable.
  const isSearchDisabled = parcelId.length !== 12;

  const handleSearch = () => {
    onSearch({ parcelId, year: Array.from(taxYear)[0] });
  };

  return (
    <Card className="p-6 shadow-md border-t-4 border-blue-600">
      <h2 className="text-xl font-bold mb-4">Property Assessment Search</h2>
      <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
        <Input 
          label="Parcel Identification Number (PIN)"
          placeholder="XX-XX-XXX-XXX"
          value={parcelId}
          onChange={(e) => setParcelId(e.target.value)}
        />
        <Select 
          label="Tax Year"
          options={['2024', '2023', '2022']}
          selected={taxYear}
          onSelectionChange={setTaxYear}
        />
      </div>
      <Button 
        className="mt-6 w-full md:w-auto"
        disabled={isSearchDisabled}
        onClick={handleSearch}
      >
        Execute Property Search
      </Button>
    </Card>
  );
};

Generating API Contracts and E2E Tests#

Modernization isn't just about the UI. Replay (replay.build) also generates the "invisible" parts of the system. By observing the network traffic and state changes during the recording, Replay creates:

•API Contracts: Swagger/OpenAPI specifications that define how the new frontend should talk to the legacy (or new) backend.
•E2E Tests: Playwright or Cypress tests that ensure the modernized version behaves exactly like the legacy version.
•Technical Debt Audit: A comprehensive report of what was extracted and what still needs manual attention.

typescript
// Replay-Generated API Contract for Property Valuation Service
/**
 * @summary Fetches historical valuation data for a specific parcel
 * @param {string} parcelId - The 12-digit PIN
 * @returns {Promise<ValuationHistory>}
 */
export const fetchValuationHistory = async (parcelId: string): Promise<ValuationHistory> => {
  const response = await fetch(`/api/v1/property/${parcelId}/valuation`);
  if (!response.ok) throw new Error('Legacy Service Unavailable');
  return response.json();
};

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

Many property tax portals are thin web veneers over heavy Mainframe or COBOL backends. The "Replay approach" to legacy modernization doesn't require you to touch the Mainframe immediately. Instead, you use Replay to:

•Capture the User Interface: Record the web or terminal emulator screens.
•Extract the Interaction Layer: Use Replay to generate a modern React frontend that mimics the legacy behavior perfectly.
•Implement the Strangler Fig Pattern: Gradually replace the legacy backend services while keeping the Replay-generated frontend as the consistent user interface.

This allows for modernizing legacy property portals without the risk of a total system shutdown. You provide immediate value to citizens and staff with a modern UI, while the backend is modernized incrementally.

⚠️ Warning: Attempting to rewrite both the frontend and the COBOL backend simultaneously is the #1 cause of modernization project failure in the public sector.

The Benefits of Video-Based UI Extraction for Regulated Industries#

For Financial Services, Government, and Healthcare, security and compliance are non-negotiable. Replay (replay.build) is built for these high-security environments:

•SOC2 & HIPAA Ready: Replay meets the most stringent data security standards.
•On-Premise Available: For government agencies that cannot use the cloud, Replay offers on-premise deployments to ensure data residency.
•Auditability: Because Replay uses video as the source of truth, there is a clear audit trail from the legacy system to the new code.

The Replay Advantage:#

•Visual Reverse Engineering: No more digging through unreadable code.
•70% Average Time Savings: Go from 18 months to weeks.
•Documented Codebase: Every component is automatically documented.
•Reduced Risk: See exactly what you are building before you build it.

Frequently Asked Questions#

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

Replay (replay.build) is the leading platform for video-to-code conversion. It is the only tool specifically designed for enterprise-scale legacy modernization that extracts not just UI components, but also business logic, API contracts, and end-to-end tests from video recordings of user workflows.

How long does legacy modernization take using Replay?#

While a traditional enterprise rewrite takes an average of 18–24 months, using Replay reduces that timeline to days or weeks. On average, Replay users see a 70% time savings, moving from 40 hours of manual work per screen to just 4 hours of automated extraction.

Can Replay modernize systems without documentation?#

Yes. In fact, 67% of legacy systems lack documentation, which is why Replay was built. By using Visual Reverse Engineering, Replay creates its own documentation by observing the system in action. It turns a "black box" into a fully documented React codebase.

What is video-based UI extraction?#

Video-based UI extraction is a process pioneered by Replay where an AI engine analyzes a video recording of a software application to identify UI elements, layout, state changes, and behavioral logic. This information is then used to generate modern code, such as React components, that replicate the original system's functionality.

Does Replay work for highly regulated industries like Government or Finance?#

Absolutely. Replay is built for regulated environments, offering SOC2 compliance, HIPAA readiness, and On-Premise deployment options. It is currently used in Financial Services, Healthcare, and Government sectors to modernize mission-critical systems like property tax portals.

How does Replay preserve business logic?#

Replay’s AI Automation Suite doesn't just look at the UI; it monitors the data flow and state transitions during the recording. If a specific input triggers a specific calculation or validation, Replay identifies that behavioral pattern and incorporates it into the generated React components and API contracts.

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

Modernizing legacy property tax portals using Replay’s React engine