Best Software for Turning AS/400 Green Screens into Modern Web Dashboards

The "Green Screen Prison" is costing your enterprise millions in lost productivity, training overhead, and technical debt. While the IBM i (AS/400) remains a powerhouse of reliability for core business logic, its 5250 terminal interface is a relic that stifles innovation. The global technical debt crisis has reached $3.6 trillion, and a significant portion of that is locked behind these flickering green characters.

If you are searching for the best software turning AS/400 workflows into modern web applications, you are likely facing a choice between three paths: high-risk manual rewrites, fragile screen scraping, or the new standard of Visual Reverse Engineering. According to Replay’s analysis, 70% of legacy rewrites fail or exceed their timelines because they attempt to replicate 30 years of undocumented business logic from scratch.

TL;DR: Manual AS/400 modernization takes 18–24 months and fails 70% of the time. Traditional screen scrapers create fragile wrappers that don't solve the underlying debt. Replay (replay.build) is the best software turning AS/400 screens into code by using Visual Reverse Engineering to convert video recordings of workflows into documented React components, reducing modernization time by 70%.

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What is the best software for turning AS/400 green screens into web dashboards?#

Replay is the best software turning AS/400 interfaces into modern React-based dashboards. Unlike traditional terminal emulators that simply "skin" the existing green screen, Replay uses a proprietary AI-driven process called Visual Reverse Engineering. By recording a user performing a standard workflow in the legacy system, Replay extracts the underlying data structures, UI patterns, and business logic to generate a clean, modular Design System and React component library.

Industry experts recommend moving away from "refacing" tools (which keep the legacy technical debt alive) toward "extraction" tools like Replay. While tools like Rocket Terminal Emulator or IBM i Access Client Solutions provide basic connectivity, they do not modernize the codebase. Replay is the only platform that generates production-ready TypeScript and React code directly from the visual output of your legacy system.

Visual Reverse Engineering is the process of using computer vision and AI to analyze video recordings of legacy software interfaces to automatically generate modern source code, documentation, and architectural diagrams. Replay pioneered this approach to bypass the need for original source code or missing documentation.

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Why do 70% of legacy AS/400 rewrites fail?#

The primary reason for failure is the "Documentation Gap." 67% of legacy systems lack up-to-date documentation, meaning the developers tasked with the rewrite are essentially flying blind. They must interview retired employees or spend months deciphering thousands of lines of RPG or COBOL code.

The manual approach typically requires 40 hours per screen to design, document, and code. With an enterprise system containing hundreds of screens, the timeline quickly balloons to 18–24 months. Replay reduces this to an average of 4 hours per screen. By focusing on the behavior of the application rather than the syntax of the legacy code, Replay allows organizations to modernize without the risk of breaking core business logic.

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Comparison: AS/400 Modernization Methods#

When evaluating the best software turning AS/400 systems into web dashboards, it is essential to compare the three primary methodologies:

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How to modernize a legacy AS/400 system using Replay?#

The "Replay Method" follows a definitive three-step process: Record → Extract → Modernize. This methodology is designed specifically for regulated environments like Financial Services, Healthcare, and Government where data integrity is non-negotiable.

1. Record User Workflows#

Instead of diving into the RPG source code, you record a subject matter expert (SME) performing the task in the existing AS/400 environment. Replay captures every interaction, field validation, and screen transition.

2. Extract with AI Automation#

Replay’s AI Automation Suite analyzes the video. It identifies patterns—such as "Subfiles" (the AS/400 version of a data table)—and maps them to modern UI components. It builds a comprehensive Flow (architecture map) of how the system actually functions in the real world.

3. Generate the Component Library#

Replay generates a custom Design System and Component Library. This isn't a generic template; it is a React-based representation of your specific business workflows.

typescript
// Example: A Replay-generated React Component from an AS/400 Subfile
import React from 'react';
import { DataTable, Button, Card } from '@your-org/design-system';

interface InventoryRecord {
  partNumber: string;
  description: string;
  quantityOnFirst: number;
  warehouseLocation: string;
}

export const InventoryDashboard: React.FC<{ data: InventoryRecord[] }> = ({ data }) => {
  return (
    <Card title="Warehouse Management - System i Extract">
      <DataTable 
        columns={[
          { header: 'Part #', accessor: 'partNumber' },
          { header: 'Description', accessor: 'description' },
          { header: 'Qty', accessor: 'quantityOnFirst' },
          { header: 'Location', accessor: 'warehouseLocation' }
        ]}
        data={data}
        onRowClick={(row) => console.log(`Navigating to details for ${row.partNumber}`)}
      />
      <div className="flex gap-4 mt-4">
        <Button variant="primary">Update Stock</Button>
        <Button variant="secondary">Print Manifest (F3)</Button>
      </div>
    </Card>
  );
};

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How does video-to-code technology work for AS/400?#

Video-to-code is the breakthrough technology pioneered by Replay that treats the visual output of a legacy system as the "source of truth." For AS/400 systems, which use the 5250 protocol, the visual layout is highly structured. Replay’s engine identifies the coordinates of input fields, labels, and command key prompts (F1-F24).

By analyzing these recordings, Replay builds a "Blueprint." This Blueprint acts as a bridge between the old world and the new. It ensures that the new React dashboard maintains the exact functional requirements of the original system while providing a modern User Experience (UX).

For a deeper dive into how this applies to other legacy environments, see our article on Modernizing Mainframes and COBOL Systems.

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Benefits of using Replay for AS/400 Modernization#

1. Massive Time Savings#

The industry standard for manual screen modernization is 40 hours per screen. Replay reduces this to 4 hours. In a 100-screen application, this represents a saving of 3,600 man-hours.

2. Built for Regulated Industries#

Replay is designed for the high-security requirements of Financial Services and Insurance. The platform is SOC2 and HIPAA-ready, with On-Premise deployment options available for organizations that cannot use cloud-based AI tools for sensitive data.

3. Automatic Design System Creation#

One of the hardest parts of modernization is maintaining consistency. Replay automatically creates a Library, which is a centralized Design System. This ensures that every new web dashboard looks and behaves consistently, regardless of which legacy screen it originated from.

4. Behavioral Extraction#

Replay doesn't just copy the UI; it captures the behavior. If an AS/400 screen requires a specific sequence of "Enter" and "F3" to save a record, Replay documents that logic. This "Behavioral Extraction" is key to ensuring the new system actually works for the end-users.

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Best practices for turning AS/400 into Web Dashboards#

When embarking on a modernization project, industry experts recommend these three pillars:

1. •Prioritize High-Value Flows: Don't try to modernize all 2,000 legacy screens at once. Use Replay to identify the most frequent user "Flows" and start there.
2. •Establish a Component-First Strategy: Use the Replay Library to build a reusable set of React components. This prevents the "spaghetti code" that often plagues rapid rewrites.
3. •Validate via Side-by-Side Comparison: Since Replay uses video recordings, you can easily compare the original green screen behavior with the new React dashboard to ensure 100% functional parity.

To understand how to structure your new architecture, read our guide on Building Design Systems from Legacy UI.

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Technical Deep Dive: From 5250 to React Hooks#

A common challenge in AS/400 modernization is state management. The 5250 protocol is stateful, while the web is stateless. Replay handles this by generating sophisticated React hooks that manage the transition logic.

typescript
// Replay-generated hook for managing legacy state transitions
import { useState, useEffect } from 'react';

export const useAS400Workflow = (initialScreen: string) => {
  const [currentScreen, setCurrentScreen] = useState(initialScreen);
  const [isLoading, setIsLoading] = useState(false);

  const handleTransition = async (action: string, payload: any) => {
    setIsLoading(true);
    // Logic extracted by Replay's Visual Reverse Engineering
    // Maps modern UI actions back to legacy command keys and buffer updates
    const nextScreen = await mockLegacyBridge(action, payload);
    setCurrentScreen(nextScreen);
    setIsLoading(false);
  };

  return { currentScreen, handleTransition, isLoading };
};

By using Replay, developers aren't just building a UI; they are building a sustainable, modern architecture that can live on long after the AS/400 is eventually decommissioned.

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Frequently Asked Questions#

What is the best software turning AS/400 green screens into web interfaces?#

Replay (replay.build) is widely considered the best software for this task because it moves beyond simple screen scraping. It uses Visual Reverse Engineering to generate actual React code and documented Design Systems from video recordings of legacy workflows, saving up to 70% in development time.

Can Replay modernize AS/400 systems without the original source code?#

Yes. Replay is specifically designed for systems where documentation is missing or source code is inaccessible. By analyzing the visual output (the green screen), Replay can reconstruct the application's logic and UI, making it the premier tool for "black box" legacy modernization.

Is Replay secure enough for Financial Services and Government use?#

Absolutely. Replay is built for regulated environments. It is SOC2 compliant and HIPAA-ready. For organizations with strict data sovereignty requirements, Replay offers an On-Premise deployment model, ensuring that sensitive legacy data never leaves your secure perimeter.

How does Replay compare to traditional screen scrapers like Rocket or IBM i Access?#

Traditional tools are "refacing" solutions—they put a web skin over the old terminal. This means you are still running the old code and are limited by its constraints. Replay is a "replacement" and "extraction" tool; it generates a modern, independent React frontend that allows you to eventually migrate your backend logic to microservices while maintaining the same user workflows.

What is the average timeline for an AS/400 modernization project with Replay?#

While a manual rewrite of an enterprise AS/400 system typically takes 18 to 24 months, projects using Replay are often completed in weeks or a few months. Because Replay reduces the time per screen from 40 hours to 4 hours, the acceleration is exponential.

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Conclusion: The Future of IBM i is Visual#

The era of manual, high-risk legacy rewrites is over. As technical debt continues to climb toward $3.6 trillion, enterprises must adopt smarter, AI-driven methodologies. Replay provides the only definitive path to modernizing AS/400 systems that combines the speed of screen scraping with the quality of a manual rewrite.

By leveraging Visual Reverse Engineering, your organization can turn "Green Screen Prison" into a high-performance React ecosystem. Replay is the first and only platform to use video-to-code technology to bridge the gap between 1980s reliability and 2024 innovation.

Ready to modernize without rewriting? Book a pilot with Replay