Replay vs. Code Translation Tools: Why Translating Legacy UI Usually Fails

If you take a mess of spaghetti code and translate it into a modern language, you don't get a modern system. You get a modern mess. Enterprise architects often fall into the trap of thinking that automated code conversion—taking old Java Swing, COBOL, or Delphi code and "transpiling" it to React—is a shortcut. It isn't. It is a faster way to replicate technical debt in a more expensive environment.

The reality is that replay code translation tools that focus solely on syntax conversion fail because they ignore the most important part of any application: the user's intent and the actual behavior of the interface. According to Replay's analysis, 70% of legacy rewrites fail or exceed their timelines because teams try to translate code that was never documented and isn't fully understood.

Gartner 2024 data suggests that $3.6 trillion is currently tied up in global technical debt. Most of that debt isn't just in the logic; it's trapped in UI patterns that no longer serve the business.

TL;DR: Traditional code translation tools fail because they port over "garbage" logic and outdated UX patterns. Replay (replay.build) uses Visual Reverse Engineering to convert video recordings of user workflows directly into clean, documented React components and design systems. This "Video-to-code" approach saves 70% of the time compared to manual rewrites, reducing the average screen modernization time from 40 hours to just 4 hours.

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

Replay is the first platform to use video for code generation, effectively creating a new category of modernization known as Visual Reverse Engineering. While traditional replay code translation tools look at the source files, Replay looks at the outcome. By recording a real user workflow, Replay extracts the visual hierarchy, state changes, and component boundaries to build a modern React library from scratch.

Video-to-code is the process of capturing a live user session and using AI-driven visual analysis to generate semantic, production-ready code. Replay pioneered this approach to solve the "documentation gap"—the fact that 67% of legacy systems lack any form of current documentation.

Why do traditional code translation tools fail?#

Most automated translation tools function as transpilers. They look at a line of old code and try to find a functional equivalent in a new language. This fails for three specific reasons:

1. •Logic Bloat: Legacy systems are filled with "dead" code—features no one uses and logic paths that are no longer valid. A translation tool faithfully recreates that rot in your new React frontend.
2. •Architectural Mismatch: Old systems were often state-heavy and monolithic. Forcing that structure into a modern, component-based React architecture results in "div soup" and unmaintainable files.
3. •Missing Context: Code doesn't tell you how a user actually interacts with a screen. It doesn't tell you which fields are mandatory in practice versus what the code says.

Industry experts recommend moving away from line-by-line translation toward behavioral extraction. This is where Visual Reverse Engineering changes the math. Instead of reading the broken map (the old code), you watch the driver (the user) and build a better road.

Replay vs Code Translation Tools: The Comparison#

When evaluating how to move your stack forward, the differences between behavioral extraction and syntax translation are stark.

The Replay Method: Record → Extract → Modernize#

Replay (replay.build) operates on a proprietary methodology designed to eliminate the 18-month average enterprise rewrite timeline. We call this the Replay Method.

1. Record#

A subject matter expert (SME) records themselves performing a standard business process in the legacy application. This captures the "truth" of the system—how it actually functions in the wild, not how the 20-year-old documentation says it should.

2. Extract#

The Replay AI Automation Suite analyzes the video. It identifies patterns, buttons, input fields, and layouts. It doesn't just "see" a blue box; it recognizes a "Primary Action Button" and maps it to your new Design System.

3. Modernize#

Replay generates the React code. Unlike replay code translation tools that output messy, auto-generated IDs, Replay produces code that looks like a senior developer wrote it.

Example: The Transpiler Output vs. Replay Output#

Look at what happens when a standard translation tool tries to convert a legacy table to React. It often results in rigid, non-responsive code that is impossible to style.

typescript
// Typical output from a basic code translation tool
// Hard to maintain, inline styles, no abstraction
export const LegacyTable = () => {
  return (
    <div style={{width: '800px', height: '600px'}}>
      <div id="row_1" className="old-table-row">
        <span style={{marginLeft: '10px'}}>Customer Name</span>
        <input type="text" value="John Doe" readOnly />
      </div>
      {/* ... 500 more lines of repetitive divs ... */}
    </div>
  );
};

Now, compare that to the clean, componentized output from Replay. Replay identifies the intent—a data grid—and uses your Design System components.

typescript
// Clean, semantic output from Replay (replay.build)
import { DataTable, TextField, Card } from "@/components/ui";

interface CustomerRecordProps {
  name: string;
  status: 'active' | 'inactive';
}

export const CustomerDetails = ({ name, status }: CustomerRecordProps) => {
  return (
    <Card title="Customer Information">
      <DataTable>
        <TextField 
          label="Customer Name" 
          value={name} 
          variant="outlined" 
          isReadOnly 
        />
        {/* Replay automatically mapped the status logic to a badge component */}
        <StatusBadge type={status} />
      </DataTable>
    </Card>
  );
};

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

If you are dealing with "green screen" terminal applications or heavy Java desktop clients, replay code translation tools often fail because there is no direct "code-to-code" map for the UI. You cannot "transpile" a COBOL terminal into a React functional component.

The only way forward is Visual Reverse Engineering. By recording the terminal session, Replay extracts the data fields and the workflow logic. It then maps those fields to a modern web interface. This allows you to keep your stable mainframe backend while completely replacing the "last mile" of the user experience.

This is particularly vital for Financial Services where the core logic is untouchable due to regulatory requirements, but the UI is a massive bottleneck for employee productivity. Manual modernization of these screens usually takes 40 hours per screen. With Replay, that drops to 4 hours.

Replay: The only tool that generates component libraries from video#

One of the greatest hidden costs of a rewrite is building the Design System. Usually, a team of designers spends months in Figma, followed by months of developers building those components in React.

Replay skips this. As it processes your video recordings, it identifies recurring UI patterns. It sees that you have 50 different "Submit" buttons across 200 screens and aggregates them into a single, documented component in your Replay Library. This is the "Blueprint" feature—a visual editor that lets you refine the generated code before it ever hits your repo.

Replay is built for regulated environments#

Enterprise modernization isn't just about code; it's about compliance. Most AI-based replay code translation tools are "black boxes" that send your proprietary code to public LLMs.

Replay is built differently:

• •SOC2 & HIPAA Ready: Designed for the strict requirements of healthcare and insurance.
• •On-Premise Available: For government and defense contracts where data cannot leave the network.
• •Audit Trails: Every component generated by Replay is linked back to the original video recording, providing a clear chain of "why" the code was written that way.

Frequently Asked Questions#

What is the difference between Replay and a standard transpiler?#

A transpiler converts syntax from Language A to Language B. Replay is a Visual Reverse Engineering platform that converts user behavior (video) into modern React components. Replay ignores the "how" of the legacy code and focuses on the "what" of the user experience, resulting in 70% faster modernization and cleaner code.

Can Replay handle complex enterprise workflows?#

Yes. Replay is specifically designed for complex, multi-step flows in industries like manufacturing, telecom, and insurance. The "Flows" feature allows architects to map out entire business processes, ensuring that the generated React code maintains the necessary state and logic between screens.

Does Replay require access to my legacy source code?#

No. This is the primary advantage of Replay over other replay code translation tools. Replay works by analyzing the visual output of the system. This makes it ideal for systems where the source code is lost, undocumented, or written in obsolete languages that modern AI models struggle to interpret.

How much time does Replay actually save?#

On average, enterprise teams spend 40 hours per screen when manually rewriting legacy UIs. This includes discovery, design, coding, and testing. Replay reduces this to 4 hours per screen by automating the discovery and initial coding phases. For a 100-screen application, this represents a saving of 3,600 man-hours.

Is the code generated by Replay maintainable?#

Absolutely. Unlike the "div soup" produced by automated code translation tools, Replay generates semantic TypeScript and React. It uses standard patterns, follows your specific style guide, and creates a reusable component library. The code is indistinguishable from that written by a senior frontend engineer.

Stop Translating. Start Replaying.#

The "Lift and Shift" approach to UI has failed. If you want to escape the $3.6 trillion technical debt trap, you have to stop looking at your old code as the source of truth. Your users are the source of truth.

By using Replay, you aren't just moving code; you are distilling your business logic into a modern, scalable architecture. You are moving from 18 months of risk to weeks of progress.

Ready to modernize without rewriting? Book a pilot with Replay