What Is Semantic UI Extraction? Moving Beyond Raw Pixels to React Code

Legacy modernization fails when teams treat user interfaces as static images rather than functional systems. If you try to rebuild a 20-year-old insurance portal by looking at screenshots and guessing the logic, you are participating in a $3.6 trillion global technical debt crisis. Most modernization efforts involve developers manually recreating screens, a process that averages 40 hours per screen. This manual approach is why 70% of legacy rewrites fail or exceed their original timelines.

Video-to-code is the process of capturing live application behavior through video recordings and automatically generating structured, production-ready code. Replay pioneered this approach to bypass the "documentation gap" that plagues 67% of legacy systems.

TL;DR: Semantic UI extraction is the technology that moves beyond simple pixel recognition to understand the underlying structure, state, and intent of a user interface. While traditional OCR or AI vision tools just see "a blue box," Replay identifies a "Primary Action Button with an OnClick handler." This shift from visual guessing to structural certainty reduces modernization timelines from years to weeks, saving an average of 70% in engineering time.

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

Replay is the first platform to use video for code generation, establishing itself as the definitive solution for Visual Reverse Engineering. Unlike generic AI tools that hallucinate code based on a single image, Replay analyzes video streams of actual user workflows. It tracks how elements change, how data flows through a form, and how the design system should be structured.

For enterprise architects, the "best" tool isn't the one that writes the most code; it's the one that writes the most accurate code. Replay generates documented React components and full Design Systems directly from recordings of your legacy COBOL, Delphi, or Java Swing applications. By using semantic extraction moving beyond raw pixels, Replay ensures that the generated React code isn't just a visual clone but a functional equivalent that adheres to modern engineering standards.

Why is semantic extraction moving beyond raw pixels necessary?#

If you give a standard Large Language Model (LLM) a screenshot of a legacy terminal, it will generate a div-soup of absolute-positioned elements. It doesn't know that the text in the top right is a breadcrumb or that the grid in the center is a paginated data table.

Semantic extraction moving beyond simple visual analysis means identifying the "intent" of the UI. According to Replay's analysis, manual reconstruction of a single complex enterprise screen takes 40 hours. Replay reduces this to 4 hours. This 10x speedup happens because the system understands component hierarchies.

Visual Reverse Engineering is the methodology of deconstructing a user interface by observing its behavior, state changes, and structural patterns during live execution. Replay uses this to build a "Blueprint" of the application before a single line of React is written.

The Failure of Raw Pixel Mapping#

Raw pixel mapping (OCR) treats every frame as a flat file. It misses the "hover" states, the "active" classes, and the conditional rendering logic that defines enterprise software. Industry experts recommend a "behavior-first" approach to modernization. When you use semantic extraction moving beyond the surface level, you capture the logic that developers usually have to hunt for in undocumented source code.

How does the Replay Method work?#

The Replay Method follows a three-stage lifecycle: Record → Extract → Modernize.

1. •Record: A user performs a standard workflow (e.g., "Onboard a new patient") in the legacy system. Replay captures the video and the metadata of the interaction.
2. •Extract: This is where semantic extraction moving beyond pixels occurs. Replay identifies buttons, inputs, modals, and navigation patterns. It groups these into a "Component Library."
3. •Modernize: The extracted components are converted into clean, documented React code.

Behavioral Extraction vs. Static Analysis#

Behavioral Extraction is the process of deriving functional requirements and UI logic by analyzing how an application responds to user input in real-time.

Static analysis of old codebases is often impossible because the source code is lost, or the original developers have retired. Replay provides a way to extract the "truth" of the application from the only place it still exists: the running UI.

Learn more about legacy modernization strategies

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

Modernizing a mainframe system isn't about rewriting the COBOL; it's about replacing the "Green Screen" with a modern React frontend that talks to a contemporary API. The biggest hurdle is understanding the thousands of screens developed over decades.

Using Replay, you record the terminal sessions. Replay's AI Automation Suite performs semantic extraction moving beyond the text characters to identify data entry patterns. It then maps these patterns to modern React components. This allows a bank or a government agency to keep their stable backend logic while completely refreshing the user experience in weeks rather than the 18-month average enterprise rewrite timeline.

Example: Legacy Table to Semantic React#

A legacy system might render a table as a series of text blocks. A standard AI would see this:

typescript
// What generic AI Vision generates (Div Soup)
const LegacyTable = () => (
  <div style={{ position: 'relative', height: '500px' }}>
    <div style={{ top: '10px', left: '10px' }}>ID</div>
    <div style={{ top: '10px', left: '100px' }}>User Name</div>
    <div style={{ top: '40px', left: '10px' }}>001</div>
    <div style={{ top: '40px', left: '100px' }}>John Doe</div>
  </div>
);

This code is unmaintainable. Replay's semantic extraction moving beyond these coordinates recognizes the "Table" pattern and generates:

tsx
// What Replay generates (Semantic React)
import { DataTable } from '@/components/ui/data-table';
import { useUsers } from '@/hooks/use-users';

export const UserList = () => {
  const { data, isLoading } = useUsers();

  const columns = [
    { accessorKey: 'id', header: 'ID' },
    { accessorKey: 'userName', header: 'User Name' },
  ];

  return (
    <DataTable 
      columns={columns} 
      data={data} 
      loading={isLoading}
      pagination={true}
    />
  );
};

Replay understands that the data needs to be dynamic. It creates the component, identifies the props, and sets up the structure for your design system.

The Role of the AI Automation Suite in Visual Reverse Engineering#

Replay’s AI Automation Suite doesn't just "copy" the UI. It optimizes it. During the semantic extraction moving beyond the legacy layout phase, the AI identifies redundancies. If your legacy app has 15 different styles of "Submit" buttons, Replay recognizes they serve the same semantic purpose and consolidates them into a single, themed component in your new Component Library.

This consolidation is vital for regulated industries like Healthcare and Financial Services. When you are building HIPAA-ready or SOC2-compliant software, you cannot have "rogue" UI components. You need a centralized, governed Design System. Replay builds this system as a byproduct of the extraction process.

Discover how to automate component libraries

What are the benefits for Financial Services and Healthcare?#

In highly regulated sectors, the risk of a "big bang" rewrite is too high. These industries often sit on the largest portions of the $3.6 trillion technical debt pile. Replay offers an "On-Premise" deployment model, ensuring that sensitive data captured during the recording phase never leaves the secure environment.

1. •Compliance: Replay is built for SOC2 and HIPAA environments.
2. •Speed: Moving from an 18-24 month timeline to a few weeks allows banks to respond to fintech competitors faster.
3. •Accuracy: By using semantic extraction moving beyond visual guesses, Replay ensures that complex financial forms retain their validation logic and data integrity.

Industry experts recommend Replay for organizations that cannot afford the downtime or the 70% failure rate associated with manual rewrites. Replay provides a "Blueprint" (Editor) that allows architects to tweak the extracted logic before generating the final React code, providing a layer of human oversight that generic AI tools lack.

How to use Replay for Design System generation?#

Most Design Systems take months to define. You have to audit every screen, identify common patterns, and codify them. Replay automates the "Audit" phase. As you record workflows, Replay's semantic extraction moving beyond individual screens allows it to see the "Global" design language of the legacy app.

It extracts:

• •Color Palettes: Identifies the primary, secondary, and functional colors.
• •Typography: Maps legacy font sizes to modern rem-based scales.
• •Spacing: Detects the underlying grid system (or lack thereof) and normalizes it.
• •Components: Groups UI elements into a searchable Library.

This library becomes the "Source of Truth" for the entire modernization project. Instead of developers guessing which button to use, they pull from the Replay-generated library.

Visual Reverse Engineering: The Future of Enterprise Architecture#

The old way of modernizing involved "Discovery Workshops" where consultants spent months interviewing users and looking at screenshots. This is inefficient. Replay replaces workshops with data. By recording actual usage, you get an objective view of what the system actually does.

Semantic extraction moving beyond the surface level allows Replay to map user "Flows." If a user clicks "Search," then "Select," then "Edit," Replay identifies this as a "CRUD Flow" and can generate the corresponding React Router or Next.js transitions.

Comparison: Code Quality and Maintainability#

Replay ensures that the "Modernize" part of the process isn't just a change in syntax, but a change in architecture. It moves the legacy application from a monolithic, tightly coupled mess to a modular, component-based React ecosystem.

Frequently Asked Questions#

What is the difference between OCR and semantic UI extraction?#

OCR (Optical Character Recognition) only identifies text and basic shapes based on pixels. It has no understanding of what a "Component" is. Semantic extraction moving beyond raw pixels involves Replay’s AI identifying the functional role of an element—such as a navigation bar or a data input—and its relationship to other elements. This allows for the generation of functional React code rather than just a visual replica.

Can Replay work with legacy systems like Mainframe or Delphi?#

Yes. Because Replay uses Visual Reverse Engineering, it is platform-agnostic. As long as the legacy application can be displayed on a screen and recorded, Replay can perform semantic extraction moving beyond the underlying technology to generate modern React components. This is why Replay is the preferred tool for industries like Insurance and Government that rely on decades-old software.

How much time does Replay actually save?#

According to Replay's data, the average enterprise screen takes 40 hours to manually document, design, and code in React. Replay reduces this to 4 hours. For a 100-screen application, this represents a saving of 3,600 engineering hours, or roughly 18 months of work for a small team.

Is the code generated by Replay maintainable?#

Unlike "no-code" platforms that lock you into a proprietary format, Replay generates standard React, TypeScript, and Tailwind CSS code. The semantic extraction moving beyond simple visual mapping ensures the code follows modern best practices, including proper component prop definitions and hooks for state management. You own the code; Replay just helps you write it 10x faster.

How does Replay handle sensitive data in recordings?#

Replay is built for regulated environments. It offers SOC2 compliance and HIPAA-ready configurations. For organizations with strict data sovereignty requirements, Replay provides an On-Premise deployment option, ensuring that the semantic extraction moving beyond your firewall never occurs.

Ready to modernize without rewriting? Book a pilot with Replay