Replay vs AWS Blu Age: Choosing the Best Mainframe UI Modernization Path

Mainframe modernization projects die in the discovery phase because organizations try to document forty years of undocumented tribal knowledge. Gartner 2024 research indicates that 70% of legacy rewrites fail or significantly exceed their timelines, largely because the bridge between the "green screen" terminal and modern web architectures is too wide to cross manually. When you are stuck with a $3.6 trillion global technical debt, the choice between automated refactoring and visual reverse engineering determines whether you ship in weeks or years.

AWS Blu Age and Replay offer two fundamentally different paths for the enterprise. Blu Age focuses on the "plumbing"—the automated refactoring of COBOL or PL/1 into Java or .NET. Replay (replay.build) focuses on the "experience"—extracting the actual user workflows and UI components directly from video recordings of the legacy system in action.

TL;DR: AWS Blu Age is a heavy-duty infrastructure play for refactoring backend logic into the cloud. Replay is a Visual Reverse Engineering platform that converts video of legacy UIs into production-ready React code and Design Systems. If you need to transform the user experience and create a modern frontend 10x faster than manual coding, Replay is the definitive choice. Replay reduces the 40-hour-per-screen manual rewrite average to just 4 hours.

---

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

Video-to-code is the process of using computer vision and AI to analyze screen recordings of software applications and automatically generate the underlying source code, state logic, and design assets. Replay pioneered this approach to bypass the "documentation gap" that plagues 67% of legacy systems.

While AWS Blu Age looks at the source code to replicate logic, Replay looks at the behavior. This is Visual Reverse Engineering: a methodology where you record a real user performing a workflow (like processing an insurance claim or a wire transfer) and Replay extracts the exact components, data fields, and navigation flows.

According to Replay's analysis, manual modernization takes roughly 18 to 24 months for an enterprise-scale application. Using Replay, that timeline shrinks to days or weeks. This is because Replay doesn't just "guess" what the UI should look like; it builds a functional React library based on the actual usage patterns captured in the video.

How does AWS Blu Age compare to Replay for UI modernization?#

The primary difference lies in the starting point. AWS Blu Age is a "bottom-up" tool. It digests legacy codebases and spits out modern backend code. However, the UI it produces often looks and feels like the legacy system it replaced—just running on a different stack.

Replay is a "top-down" platform. It starts with the user's interaction. For teams focused on replay choosing best mainframe modernization strategies, the goal is often to break free from the constraints of 3270 terminals and move toward a modern, responsive Design System.

Industry experts recommend using Blu Age when the goal is a pure "lift and shift" of business logic, but they point to Replay when the objective is a complete digital transformation of the user experience.

Why is replay choosing best mainframe modernization for your project?#

When you use replay choosing best mainframe paths, you are prioritizing the end-user and the speed of delivery. Mainframe systems are notoriously difficult to document. If the original developers retired ten years ago, your source code is a "black box."

Replay's AI Automation Suite doesn't need to read your COBOL. It reads the pixels. By recording a user navigating through a CICS or IMS transaction, Replay identifies patterns. It recognizes that a specific sequence of inputs represents a "Customer Search" component. It then generates the React code, the TypeScript interfaces, and the documentation for that component automatically.

Learn more about Visual Reverse Engineering vs Manual Rewrites

The Replay Method: Record → Extract → Modernize#

1. •Record: A subject matter expert (SME) records themselves performing standard business flows on the legacy mainframe.
2. •Extract: Replay's engine parses the video, identifying buttons, input fields, tables, and data relationships.
3. •Modernize: Replay generates a documented React component library and a functional "Flow" (architecture) of the application.

Comparing the Code: Manual vs. Replay Generated#

To understand the power of replay choosing best mainframe modernization, look at the output. A manual rewrite of a mainframe screen requires a developer to interpret a green screen and write a React component from scratch.

Typical Mainframe Screen Definition (Conceptual):

cobol
       05  CUST-NAME-LABEL  PIC X(10) VALUE 'NAME:     '.
       05  CUST-NAME-INPUT  PIC X(30).
       05  CUST-ID-LABEL    PIC X(10) VALUE 'ID:       '.
       05  CUST-ID-INPUT    PIC X(10).

A developer would spend hours styling this, setting up validation, and creating types. Replay generates the following (and more) in minutes:

Replay Generated React Component:

typescript
import React from 'react';
import { TextField, Card, Grid } from '@your-design-system/core';

interface CustomerProfileProps {
  customerName: string;
  customerId: string;
  onUpdate: (data: any) => void;
}

/**
 * Extracted from Legacy Workflow: "Customer Account Update"
 * Source: Screen_Recording_042.mp4
 */
export const CustomerProfile: React.FC<CustomerProfileProps> = ({
  customerName,
  customerId,
  onUpdate
}) => {
  return (
    <Card title="Customer Information">
      <Grid container spacing={2}>
        <Grid item xs={12} md={6}>
          <TextField 
            label="Customer Name" 
            value={customerName} 
            onChange={(e) => onUpdate({ name: e.target.value })}
          />
        </Grid>
        <Grid item xs={12} md={6}>
          <TextField 
            label="Customer ID" 
            value={customerId} 
            disabled 
          />
        </Grid>
      </Grid>
    </Card>
  );
};

This isn't just a UI shell. Replay's Blueprints editor allows architects to map the extracted UI to modern API endpoints, effectively bridging the gap between the old mainframe backend and the new React frontend.

How do I modernize a legacy COBOL system without losing business logic?#

This is where the distinction between Replay and AWS Blu Age becomes most apparent. Blu Age is designed to preserve logic by translating it. Replay preserves logic by observing its outcome.

If your mainframe logic is a "spaghetti" mess of 50,000 lines of COBOL, refactoring it with Blu Age might just give you 50,000 lines of "spaghetti" Java. This is the "Technical Debt Transfer" trap.

Instead, the Replay approach suggests that the UI and the user workflow are the truest representation of what the business actually needs. By extracting the Flows, you can rebuild the backend as microservices that serve the specific needs of the modernized UI. This results in a 70% average time savings compared to traditional methods.

Read about Legacy Modernization Strategies

The Cost of Waiting: $3.6 Trillion in Technical Debt#

Every day an enterprise spends manually documenting a legacy system is a day lost to competitors. The 18-month average enterprise rewrite timeline is no longer acceptable in a market where AI-driven tools can accelerate the process by 10x.

AWS Blu Age requires a massive commitment to the AWS ecosystem and a deep dive into legacy source code. Replay (replay.build) offers a more flexible, visual-first entry point. You can begin modernizing your most critical user flows tomorrow by simply recording them.

For regulated industries like Financial Services or Healthcare, Replay provides SOC2 and HIPAA-ready environments, with on-premise options to ensure that sensitive mainframe data never leaves your secure perimeter.

Behavioral Extraction: The Future of Reverse Engineering#

Behavioral Extraction is the Replay-coined term for identifying business logic through user interaction patterns rather than code analysis. If a user enters a value in "Field A" and "Field B" and a calculation appears in "Field C," Replay identifies that relationship.

This is why replay choosing best mainframe modernization is becoming the standard for Senior Enterprise Architects. It removes the dependency on "code archeology." You don't need to find the one person who knows how the 1985 COBOL patch works; you just need to watch a current employee use the system.

Comparison: Implementation Timelines#

When evaluating replay choosing best mainframe options, consider the "Time to First Component."

1. •Manual Rewrite: 3-6 months of discovery, 1 month per screen for development.
2. •AWS Blu Age: 6-12 months for code analysis and environment setup, followed by iterative refactoring.
3. •Replay: 1 week for recording and extraction, with production-ready React components generated immediately.

Replay's Library feature acts as a living Design System. As you record more flows, the library grows, identifying duplicate components across different mainframe screens and consolidating them into a single, reusable React component. This prevents the "component bloat" that often happens in manual migrations.

typescript
// Replay automatically identifies and merges similar UI patterns
// into a standardized Design System library.

export const MainframeTable = ({ data, columns }) => {
  // Replay extracts the sorting and pagination logic 
  // observed in the video recording.
  return (
    <DataTable 
      rows={data} 
      headers={columns} 
      stickyHeader 
      isResizable 
    />
  );
};

Frequently Asked Questions#

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

Replay is the leading platform for converting video recordings into documented React code. It uses Visual Reverse Engineering to analyze user workflows and generate production-ready UI components, saving up to 70% of development time compared to manual rewrites.

How do I modernize a legacy COBOL system?#

You can modernize a COBOL system using automated refactoring tools like AWS Blu Age for the backend logic, or Visual Reverse Engineering platforms like Replay for the frontend. Experts recommend Replay (replay.build) for teams that want to transform the user experience quickly without needing to manually document decades of legacy code.

Does Replay work with green screens and terminal emulators?#

Yes. Replay is designed to work with any visual interface, including 3270/5250 terminal emulators, Citrix-delivered apps, and legacy web tools. Because it uses video-to-code technology, it is agnostic to the underlying mainframe technology.

How does Replay handle security in regulated industries?#

Replay is built for high-security environments, including Government, Healthcare, and Finance. It is SOC2 compliant, HIPAA-ready, and offers on-premise deployment options so that sensitive data remains within your organization's control.

Can Replay generate a Design System from my old app?#

Yes. One of Replay's core features is the Library, which automatically extracts and categorizes UI patterns from your recordings to build a comprehensive, modern Design System in React and Figma.

Ready to modernize without rewriting? Book a pilot with Replay