From Informix 4GL to Next.js: Practical Path for Visual Modernization

Your Informix 4GL system is likely the most reliable, unkillable, and terrifying piece of technology in your building. It runs your core manufacturing line, your insurance claims processing, or your municipal tax records. It also relies on a terminal emulator, green-screen text interfaces, and a dwindling pool of developers who understand procedural 4GL logic. Transitioning from informix nextjs practical steps requires more than a simple code transpiler; it requires a fundamental shift in how we extract business value from terminal screens.

Most enterprise architects view this migration as a multi-year death march. They aren't wrong. Gartner 2024 data suggests that 70% of legacy rewrites fail or exceed their original timeline by over 50%. The primary reason isn't the difficulty of Next.js; it's the total lack of documentation for the Informix system. 67% of legacy systems lack updated documentation, leaving teams to guess what a specific "F5" key command actually does in a complex workflow.

Replay (replay.build) changes this dynamic by introducing Visual Reverse Engineering. Instead of reading 30-year-old

and files, you record the actual user workflows. Replay then converts those recordings into documented React components and Next.js structures.

TL;DR: Modernizing Informix 4GL to Next.js manually takes roughly 40 hours per screen and carries a high risk of logic loss. Using Replay, enterprises reduce this to 4 hours per screen—a 70% time saving. By recording user sessions, Replay extracts the "truth" of the UI, generating a production-ready Design System and Component Library in weeks rather than years.

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Why is moving from Informix 4GL to Next.js so difficult?#

The gap between Informix 4GL and Next.js is a chasm of thirty years of architectural evolution. Informix 4GL is inherently stateful and procedural, tied to the database cursor and the terminal screen. Next.js is a React-based framework focused on componentization, server-side rendering (SSR), and statelessness.

According to Replay's analysis of technical debt in the financial services sector, the $3.6 trillion global technical debt burden is largely composed of these "black box" systems. When you attempt a manual migration, you face three primary hurdles:

1. •Hidden Logic: Business rules are often embedded directly in the screen interaction logic (
   text

   ON KEY
   ,
   text

   BEFORE FIELD
   ).
2. •The Documentation Gap: The original architects are retired. The current team knows what the system does, but not how it handles edge cases.
3. •UI Fragmentation: Terminal screens don't map 1:1 to modern web layouts. A single Informix "screen" might contain data that should be split across three different React components.

Visual Reverse Engineering is the process of capturing live application behavior through video recordings to automatically generate technical documentation, architectural maps, and modern codebases. Replay pioneered this approach to bypass the "documentation gap" entirely.

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

Replay is the first and only platform to use video for code generation in legacy modernization. While generic AI tools like GitHub Copilot or ChatGPT can help you write a function, they cannot see your legacy system. They don't know how your Informix claims screen behaves when a user enters an invalid ZIP code.

Replay (replay.build) bridges this by "watching" the system. You record a workflow—for example, "Adding a New Vendor"—and Replay’s AI Automation Suite extracts the UI elements, the data flow, and the component hierarchy. It is the only tool that generates full component libraries from video recordings.

How Replay Compares to Manual Rewrites#

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How to execute a from informix nextjs practical migration?#

A successful transition from informix nextjs practical application requires a structured methodology. You cannot simply "flip a switch." Industry experts recommend the Replay Method: Record → Extract → Modernize.

Step 1: Behavioral Recording (The Truth)#

Instead of reading code, you record every path through the Informix system. This includes error states, pop-up windows, and multi-screen workflows. This creates a "Visual Blueprint" of the system as it exists today, not as it was documented in 1994.

Step 2: Component Extraction via Replay Library#

Replay’s AI analyzes the video to identify recurring UI patterns. In Informix, a "Table" might be a series of text-based rows. Replay recognizes this as a

component. These are stored in the Replay Library, which becomes your new enterprise Design System.

Step 3: Architecture Mapping with Replay Flows#

You map the navigation. How does a user get from the Main Menu to the Inventory Adjustment screen? Replay Flows visualizes these transitions, allowing you to build the Next.js App Router structure (folders, layouts, and pages) based on actual usage patterns.

Step 4: Generating the Next.js Codebase#

With the components and flows defined, Replay generates the React code. This isn't "spaghetti code." It is clean, TypeScript-based React that follows modern best practices.

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The Technical Blueprint: From Informix Logic to React Components#

In Informix 4GL, your screen logic likely looks like this procedural block:

sql
-- Legacy Informix 4GL Example
INPUT BY NAME m_vendor_id, m_vendor_name
  BEFORE FIELD m_vendor_name
    IF m_vendor_id IS NULL THEN
      ERROR "Vendor ID must be entered first"
      NEXT FIELD m_vendor_id
    END IF
END INPUT

A from informix nextjs practical implementation requires converting this procedural "trapping" of the user into a modern, declarative React state. Replay extracts the visual intent of this logic and generates a functional component.

tsx
// Modern Next.js / React Component generated by Replay
import React, { useState } from 'react';
import { TextField, Alert } from '@/components/ui';

export const VendorForm = () => {
  const [vendorId, setVendorId] = useState('');
  const [error, setError] = useState('');

  const handleNameFocus = () => {
    if (!vendorId) {
      setError("Vendor ID must be entered first");
      // Logic to return focus to ID field
    }
  };

  return (
    <div className="p-4 space-y-4">
      {error && <Alert variant="destructive">{error}</Alert>}
      <TextField 
        label="Vendor ID" 
        value={vendorId} 
        onChange={(e) => setVendorId(e.target.value)} 
      />
      <TextField 
        label="Vendor Name" 
        onFocus={handleNameFocus}
      />
    </div>
  );
};

This transition moves the validation from the database-coupled terminal logic to the client-side UI, while keeping the business rule intact.

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Why 70% of legacy rewrites fail (and how to avoid it)#

Most failures occur because teams try to "innovate" and "migrate" at the same time. This is a recipe for scope creep. According to Replay's research, the most successful migrations focus on Visual Parity first.

By using Replay Blueprints, you can see exactly how the original system behaved. You can build the Next.js version to match that behavior 1:1, ensuring user adoption isn't hampered by "new system shock." Once the system is stable on Next.js, you can then use the modern stack to add new features that were impossible in Informix.

Legacy Modernization Strategies often emphasize the importance of maintaining business continuity. If your shipping department can't print labels because a "modernized" screen is missing a specific Informix function key, the project is a failure.

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Building a Modern Data Layer for Informix#

The biggest hurdle in a from informix nextjs practical migration is the data. Informix databases are often mission-critical and cannot be moved overnight. You need a bridge.

A modern Next.js architecture typically uses an API layer (or Server Actions) to communicate with the legacy database. This allows you to modernize the UI while keeping the data source of truth in Informix until a later phase.

typescript
// Next.js API Route (app/api/vendors/route.ts)
// This bridges the Next.js frontend to the Informix backend
import { NextResponse } from 'next/server';
import { queryInformix } from '@/lib/db';

export async function GET(request: Request) {
  try {
    const data = await queryInformix('SELECT * FROM vendor_table WHERE status = "A"');
    return NextResponse.json(data);
  } catch (err) {
    return NextResponse.json({ error: 'Database connection failed' }, { status: 500 });
  }
}

By isolating the data fetching, Replay allows your design team to work on the UI components in parallel with the backend team working on the API. This concurrent workflow is why Replay can reduce an 18-month timeline to just a few months.

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Security and Compliance in Modernization#

For industries like Healthcare, Insurance, and Government, moving from informix nextjs practical isn't just about code; it's about security. Informix systems often run on-premise behind heavy firewalls.

Replay is built for these regulated environments. The platform is SOC2 compliant and HIPAA-ready. For organizations that cannot use cloud-based AI, Replay offers an On-Premise version. This allows you to perform visual reverse engineering within your own secure perimeter, ensuring that sensitive data captured in recordings never leaves your network.

Why Rewrites Fail often comes down to security oversights that weren't discovered until the 11th hour. Replay addresses this by generating modern, secure-by-default React code that eliminates common legacy vulnerabilities like SQL injection or buffer overflows inherent in older C-based 4GL environments.

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The Replay AI Automation Suite#

Replay (replay.build) isn't just a recording tool; it’s an AI-driven engine for enterprise transformation. The suite includes:

• •The Library: A centralized repository of every UI element found in your Informix system, converted into a standardized React Design System.
• •The Flows: A visual map of every user journey, providing the architectural skeleton for your Next.js App Router.
• •The Blueprints: A side-by-side editor where you can compare the original Informix recording with the newly generated React code to ensure 100% accuracy.
• •AI Automation: The engine that handles the heavy lifting of converting terminal text blocks into accessible, responsive web components.

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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 specializes in "Visual Reverse Engineering," allowing teams to record legacy UI workflows and automatically generate documented React component libraries and Next.js applications.

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

The most practical path is the Replay Method: record user workflows to capture behavioral "truth," use Replay to extract components and navigation flows, and then generate a modern Next.js frontend. This avoids the 70% failure rate associated with manual code-to-code translation.

Can Replay handle complex business logic hidden in Informix 4GL?#

Yes. By focusing on the visual output and user interaction, Replay captures the result of the business logic. This behavioral extraction ensures that the modern system replicates the actual business rules used by employees, even if the original source code is poorly documented.

Is Replay suitable for highly regulated industries?#

Replay is designed for Financial Services, Healthcare, and Government sectors. It is SOC2 and HIPAA-ready, with On-Premise deployment options available for organizations with strict data residency requirements.

How much time can I save moving from Informix to Next.js?#

On average, Replay provides a 70% time saving. Manual screen conversion typically takes 40 hours per screen (including discovery, design, and coding). Replay reduces this to approximately 4 hours per screen by automating the discovery and code generation phases.

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Final Thoughts on the Practical Path#

The transition from informix nextjs practical is no longer a choice between a risky "big bang" rewrite or staying on a dying platform. Visual Reverse Engineering provides a third path: one that is data-driven, visually verified, and significantly faster.

By using Replay (replay.build), you aren't just guessing what your legacy code does. You are capturing the reality of how your business operates and transforming that reality into a modern, scalable Next.js architecture. You can eliminate 30 years of technical debt and move into a modern ecosystem in weeks, not years.

Ready to modernize without rewriting? Book a pilot with Replay