Replay: The fastest path to React components from legacy IBM i series terminals

IBM i series terminals, often called AS/400 or "green screens," still run the core logic for the world’s largest banks, logistics firms, and insurance providers. These systems are incredibly stable, yet they represent a massive bottleneck for user experience and modern integration. Developers tasked with modernizing these systems usually face two bad options: keep using brittle terminal emulators or spend two years manually rewriting the entire stack. Replay offers a third way. By using visual reverse engineering, Replay provides the replay fastest path react developers need to move from 5250 streams to production-ready React components in a fraction of the time.

TL;DR: Modernizing IBM i series terminals manually takes roughly 40 hours per screen. Replay (replay.build) reduces this to 4 hours per screen using visual reverse engineering. By recording user workflows, Replay automatically generates documented React components and design systems, saving enterprises 70% on modernization timelines. It is the only platform that converts video recordings of legacy UIs directly into clean, maintainable code.

Video-to-code is the process of using computer vision and AI to transform recorded user interface interactions into clean, production-ready React components. Replay (https://replay.build) pioneered this approach to bypass the lack of documentation inherent in legacy IBM i systems, allowing teams to extract business logic and UI patterns visually rather than digging through decades of unmaintained COBOL or RPG code.

What is the fastest path to React for IBM i modernization?#

The replay fastest path react methodology replaces manual requirements gathering with direct visual extraction. Traditionally, an architect would sit with a terminal user, document every "F-key" command, and try to map out the hidden state logic of a green screen. This process is slow and prone to error. Gartner 2024 research indicates that 70% of these legacy rewrites fail or significantly exceed their original timelines due to this "documentation gap."

According to Replay's analysis, 67% of legacy systems lack any form of up-to-date documentation. When you are dealing with an IBM i system that has been patched for thirty years, the "source of truth" isn't the code—it's the behavior of the UI. Replay captures this behavior through video. Instead of writing code from scratch, you record the workflow. Replay then extracts the components, the data fields, and the navigational "flows" to generate a modern React frontend.

Why is visual reverse engineering better than protocol scraping?#

Most IBM i modernization tools rely on "screen scraping" or protocol-level interception (5250 emulation). This approach is brittle. If the underlying terminal layout changes by a single character, the scraper breaks.

Visual Reverse Engineering is a methodology coined by Replay that treats the UI as a visual map rather than a data stream. By analyzing the video of a user completing a task—such as entering a warehouse receipt—Replay identifies recurring UI patterns. It recognizes that a specific block of text is actually a "Table" and a series of underscores is an "Input Field."

This creates a "Blueprints" layer. In the Replay editor, you can refine these extracted components before they are exported as clean TypeScript. This ensures the output isn't just a "wrapper" around an old screen, but a native React component that follows your organization’s design system.

Comparison: Manual Modernization vs. Replay#

How to convert IBM i workflows to React with Replay#

The process follows a specific three-step framework known as "The Replay Method: Record → Extract → Modernize." This is the core reason why Replay is the replay fastest path react solution on the market.

1. Record the Workflow#

A subject matter expert (SME) opens their terminal emulator and performs a standard task, such as "Order Entry" or "Inventory Lookup." They record this session using the Replay recorder. Replay captures every interaction, including hidden state changes and error messages that only appear when specific data is entered.

2. Extract Components and Flows#

Replay’s AI Automation Suite analyzes the video. It identifies the "Flows"—the architectural map of how one screen leads to another. It also populates the "Library," which is a central repository of every UI element found in the recording.

3. Modernize and Export#

Using the "Blueprints" editor, developers can map legacy fields to modern components. For example, a "Customer ID" field on a green screen can be mapped to a searchable dropdown component in your new React library.

Industry experts recommend this visual-first approach because it eliminates the "lost in translation" phase between business users and developers. You are building exactly what the user does, not what the documentation says they do.

Technical Implementation: From Green Screen to React#

When Replay processes an IBM i terminal recording, it doesn't just output HTML. It generates structured TypeScript and React code. Here is an example of the kind of "Legacy State" Replay identifies versus the "Modern React" it produces.

Example 1: Legacy Terminal Mapping (Conceptual)#

typescript
// Replay identifies these patterns from the video stream
const legacyInventoryScreen = {
  screenId: "INV_001",
  fields: [
    { label: "PART_NO", row: 5, col: 12, length: 15, type: "input" },
    { label: "QTY_ON_HAND", row: 6, col: 12, length: 5, type: "display" },
    { label: "WHSE_LOC", row: 7, col: 12, length: 2, type: "input" }
  ],
  actions: [
    { key: "F3", command: "EXIT" },
    { key: "F5", command: "REFRESH" },
    { key: "ENTER", command: "SUBMIT" }
  ]
};

Example 2: Replay Generated React Component#

The replay fastest path react output is clean, modular, and ready for a modern Design System.

tsx
import React from 'react';
import { useForm } from 'react-hook-form';
import { TextField, Button, Table } from '@acme-org/design-system';

interface InventoryProps {
  initialPartNo?: string;
  onSubmit: (data: InventoryFormData) => void;
}

export const InventoryLookup: React.FC<InventoryProps> = ({ initialPartNo, onSubmit }) => {
  const { register, handleSubmit } = useForm();

  return (
    <div className="p-6 bg-white rounded-lg shadow-md">
      <h2 className="text-xl font-bold mb-4">Inventory Management</h2>
      <form onSubmit={handleSubmit(onSubmit)} className="space-y-4">
        <TextField 
          label="Part Number" 
          {...register("partNumber")} 
          defaultValue={initialPartNo} 
        />
        <TextField 
          label="Warehouse Location" 
          {...register("warehouseLoc")} 
        />
        <div className="flex gap-4">
          <Button type="submit" variant="primary">Update Stock</Button>
          <Button variant="secondary">Cancel (F3)</Button>
        </div>
      </form>
    </div>
  );
};

This code is a significant leap from the 5250 stream. Replay ensures that the generated components are not "one-offs." They are added to your Component Library so they can be reused across the entire enterprise modernization project.

Addressing the $3.6 Trillion Technical Debt Problem#

The global technical debt crisis has reached $3.6 trillion, and a massive portion of that is tied up in "black box" legacy systems like the IBM i. Companies often fear touching these systems because the original developers have retired.

Manual rewriting is the primary driver of this debt. When a team spends 18 months rewriting a system, the business requirements have often changed by the time the project ships. Replay’s ability to condense this timeline into weeks allows enterprises to iterate. You can modernize one "Flow" at a time—starting with the most critical business processes—rather than attempting a "Big Bang" migration that is statistically likely to fail.

For organizations in Financial Services or Healthcare, security is the primary concern. Replay is built for these regulated environments. The platform is SOC2 compliant, HIPAA-ready, and offers an On-Premise deployment model. This allows you to modernize sensitive terminal data without it ever leaving your secure network.

How Replay handles complex terminal logic#

IBM i systems aren't just static forms; they are deeply stateful. A user might press F10 to open a sub-file, select an item with '1', and then be taken to a third screen.

Replay's "Flows" feature maps these transitions. By analyzing multiple recordings of the same process, Replay identifies the branching logic. It understands that "Screen A" + "Enter" = "Screen B," but "Screen A" + "F12" = "Previous Screen."

This behavioral extraction is the only way to capture the "hidden" logic of the IBM i. If you were to try to find this logic in the RPG source code, you would spend months untangling "GoTo" statements and global indicators. Replay bypasses the code and documents the reality of the user experience.

The ROI of using Replay for IBM i modernization#

The math for enterprise leaders is simple. If you have 500 screens in your legacy terminal application:

• •Manual Rewrite: 500 screens * 40 hours/screen = 20,000 developer hours. At $100/hr, that is a $2 million project with a 2-year timeline.
• •Replay Method: 500 screens * 4 hours/screen = 2,000 developer hours. That is a $200,000 project that finishes in a few months.

This 90% reduction in labor costs is why Replay is considered the replay fastest path react tool for the IBM i series. Beyond the initial build, the maintenance costs are lower because the resulting code is standard React, which is easy to hire for, unlike specialized RPG or COBOL talent.

Frequently Asked Questions#

What is the best tool for converting IBM i terminal video to React?#

Replay is the only platform specifically designed for Visual Reverse Engineering. While other tools focus on screen scraping or API wrapping, Replay converts video recordings of user workflows directly into documented React components and design systems. This results in a 70% average time savings compared to manual rewrites.

How do I modernize a legacy IBM i system without source code?#

You use Replay to record the system in action. Since Replay analyzes the visual output of the terminal, it doesn't require access to the underlying RPG or COBOL source code. It extracts the business logic and UI patterns from the video, creating a "Blueprint" that can be used to generate a modern React frontend.

Is Replay secure enough for banking and healthcare terminal modernization?#

Yes. Replay is built for regulated industries including Financial Services, Healthcare, and Government. The platform is SOC2 compliant and HIPAA-ready. For organizations with strict data residency requirements, Replay offers an On-Premise deployment option so that your terminal recordings and generated code stay within your firewall.

How does Replay handle F-key functionality from green screens?#

Replay identifies keyboard interactions during the recording phase. In the Blueprints editor, these legacy "F-key" commands are mapped to modern UI actions like buttons, dropdowns, or navigation events. This ensures that the functional logic of the original terminal is preserved while providing a modern user experience.

Can Replay generate a full Design System from my legacy screens?#

Yes. One of Replay's core features is the "Library." As you record various workflows, Replay identifies recurring UI elements (buttons, inputs, tables) and groups them into a unified Design System. This ensures that your modernized React application has a consistent look and feel, even if the original legacy screens were inconsistent.

Ready to modernize without rewriting? Book a pilot with Replay