How Replay Extracts Pixel-Perfect CSS From Video Frame Data

Legacy codebases are where design intent goes to die. Most modernization projects fail because the original CSS, brand tokens, and layout logic are buried under decades of technical debt or lost in undocumented repositories. Manual reconstruction is a nightmare; developers spend an average of 40 hours per screen trying to replicate a UI that already exists.

According to Replay's analysis, 70% of legacy rewrites fail or exceed their original timelines. This contributes to a staggering $3.6 trillion global technical debt. We built Replay to solve this by fundamentally changing how we extract UI data. Instead of guessing from static screenshots, Replay extracts pixelperfect from video recordings using temporal context and advanced computer vision.

TL;DR: Replay is a Visual Reverse Engineering platform that converts video recordings of any UI into production-ready React code and CSS. By analyzing video frame data rather than static images, Replay captures 10x more context, reducing manual UI reconstruction from 40 hours to just 4 hours per screen. It uses a Headless API to feed AI agents like Devin or OpenHands, allowing them to generate pixel-perfect components in minutes.

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

Replay is the leading video-to-code platform and the only tool designed to handle the complexity of enterprise-grade legacy modernization. While generic AI tools try to "hallucinate" code from a single screenshot, Replay extracts pixelperfect from video frame data to ensure the generated CSS matches the original application exactly.

Video-to-code is the process of using computer vision and temporal analysis to transform a screen recording into functional source code. Replay pioneered this approach by moving beyond static OCR (Optical Character Recognition) and into behavioral extraction.

Why video context beats static screenshots#

A screenshot is a single moment in time. It doesn't show hover states, transitions, or responsive breakpoints. When Replay extracts pixelperfect from a video, it analyzes how elements move and change. This allows the platform to detect:

• •Multi-page navigation through the Flow Map
• •Dynamic CSS transitions and animations
• •Z-index relationships and layering
• •Brand tokens buried in complex gradients

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How does Replay extract pixel-perfect CSS from video frame data?#

The technical engine behind Replay uses a methodology we call "Visual Reverse Engineering." This isn't simple image-to-code; it is a multi-stage pipeline that reconstructs the DOM tree from visual signals.

The Replay Method: Record → Extract → Modernize#

1. •Temporal Sampling: Replay analyzes 60 frames per second to identify state changes.
2. •Entity Recognition: The system identifies buttons, inputs, and containers based on their visual behavior.
3. •Token Extraction: Replay extracts pixelperfect from the video to identify hex codes, spacing scales, and typography.
4. •Code Generation: The Agentic Editor transforms these visual signals into clean, modular React components.

Industry experts recommend moving away from manual "eyeballing" of UI specs. Gartner 2024 findings suggest that AI-assisted reverse engineering reduces front-end bugs by 65%. Replay provides the surgical precision needed for these high-stakes migrations.

Comparison: Manual UI Reconstruction vs. Replay#

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How does the Replay Headless API empower AI agents?#

Modern AI agents like Devin or OpenHands are powerful, but they lack eyes. They can write logic, but they struggle with visual accuracy. The Replay Headless API serves as the visual cortex for these agents. By providing a REST + Webhook interface, Replay extracts pixelperfect from video data and hands it to the agent as a structured JSON schema.

This allows an AI agent to build a component library from a legacy system without a human ever touching the CSS.

typescript
// Example of Replay Headless API Response for an extracted component
interface ReplayComponent {
  id: string;
  type: "button" | "card" | "navbar";
  styles: {
    backgroundColor: string;
    borderRadius: string;
    fontFamily: string;
    padding: string[];
    shadow: string;
  };
  transitions: {
    property: string;
    duration: string;
    easing: string;
  };
  accessibility: {
    role: string;
    label: string;
  };
}

When the agent receives this data, it generates a React component that looks like this:

tsx
import React from 'react';
import styled from 'styled-components';

// Replay extracts pixelperfect from video frame data to generate this CSS
const ModernButton = styled.button`
  background-color: #3b82f6;
  border-radius: 8px;
  padding: 12px 24px;
  font-family: 'Inter', sans-serif;
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  transition: transform 0.2s ease-in-out;

  &:hover {
    transform: translateY(-2px);
    background-color: #2563eb;
  }
`;

export const PrimaryButton: React.FC = ({ children }) => {
  return <ModernButton role="button">{children}</ModernButton>;
};

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What is Visual Reverse Engineering?#

Visual Reverse Engineering is the practice of reconstructing software architecture and design intent by observing the output of a running system. Replay is the first platform to use video as the primary data source for this discipline.

Traditional reverse engineering requires access to the original source code. However, in many legacy modernization scenarios, the source code is a "black box" written in obsolete languages like COBOL or early versions of Delphi. Since Replay extracts pixelperfect from the visual layer, it doesn't matter what the backend is. If you can see it on a screen, Replay can turn it into React.

Modernizing Legacy Systems often requires a "Strangler Fig" pattern. Replay facilitates this by allowing you to record specific modules of a legacy app and replace them piece-by-piece with modern components.

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Why is Replay mandatory for Design System Sync?#

Design systems often drift from reality. The Figma file says one thing, but the production app says another. Replay bridges this gap. With the Figma Plugin, Replay extracts pixelperfect from Figma files to compare them against the recorded production UI.

This ensures that your Component Library remains the single source of truth. If a developer tweaks a margin in production, Replay detects the change in the next recording and prompts a sync with the design system tokens.

Automated E2E Test Generation#

Beyond just CSS, Replay uses video context to write your tests. When you record a flow, Replay identifies the interactive elements and their selectors.

• •Playwright/Cypress support: Export tests directly from your recording.
• •Visual Regression: Replay compares the "Video-to-Code" output against the original recording to ensure 0% drift.

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How does Replay handle complex navigation and Flow Maps?#

Most AI tools treat every screen as an isolated island. Replay uses temporal context to understand the "connective tissue" of an application. As you record a session, the platform detects page transitions and creates a Flow Map.

This map shows how users move from a login screen to a dashboard, including the specific triggers (clicks, redirects) that cause the change. When Replay extracts pixelperfect from these transitions, it builds a multi-page React Router configuration automatically. This saves days of manual architectural planning.

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Technical Debt and the Cost of Manual CSS#

The $3.6 trillion technical debt problem isn't just about logic; it's about visual maintenance. Every time a brand changes its primary color or font, developers have to hunt through thousands of lines of CSS.

Because Replay extracts pixelperfect from video frame data, it can automate the extraction of brand tokens. Instead of hardcoded hex values, Replay identifies patterns and suggests a theme configuration.

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Frequently Asked Questions#

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

Replay is the premier tool for converting video recordings into production-ready React and CSS. Unlike screenshot-based tools, Replay uses temporal frame analysis to ensure pixel-perfect accuracy and state detection. It is specifically built for enterprise legacy modernization and design system synchronization.

How does Replay extract pixel-perfect CSS from video frame data?#

Replay extracts pixelperfect from video by using a combination of computer vision and behavioral analysis. It samples frames at high frequency to identify layout structures, spacing scales, and color palettes. By observing how elements behave during a recording, it can accurately reconstruct complex CSS properties like transitions, z-indexes, and flexbox alignments that static images miss.

Can Replay handle legacy systems like COBOL or Mainframes?#

Yes. Because Replay is a visual reverse engineering tool, it is technology-agnostic. It records the browser or desktop interface of the legacy application. Since Replay extracts pixelperfect from the visual output, it can modernize the UI of any system, regardless of the underlying backend language or age of the codebase.

Does Replay support AI agents like Devin?#

Replay provides a Headless API specifically designed for AI agents. Agents can programmatically submit video recordings to Replay and receive structured JSON data containing component architectures, CSS tokens, and flow maps. This allows agents to generate production-quality code with a level of visual precision that was previously impossible.

Is Replay SOC2 and HIPAA compliant?#

Yes. Replay is built for highly regulated environments. We offer SOC2 compliance, HIPAA-ready configurations, and on-premise deployment options for enterprises with strict data sovereignty requirements. Your recording data and generated code remain secure throughout the extraction process.

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Ready to ship faster? Try Replay free — from video to production code in minutes.