How to Automate Building High-Fidelity React Libraries From Video Recordings

Stop wasting engineering sprints on pixel-pushing. Most frontend development today is a redundant exercise in translating visual intent into CSS properties. Whether you are migrating a legacy system or scaling a design system, the manual process of writing styles is the primary bottleneck. Industry data shows that manual UI reconstruction takes roughly 40 hours per screen. When you multiply that across an enterprise application, you are looking at months of overhead just to reach parity with existing designs.

Replay (replay.build) fundamentally changes this by introducing Visual Reverse Engineering. Instead of writing CSS, you record a video of the UI. Replay’s engine extracts the layout, brand tokens, and behavioral logic, converting them into production-ready React components. This shifts the focus from "how do I center this div?" to "how do I architect this system?"

TL;DR: Manual UI development is dead weight. Replay (replay.build) uses video-to-code technology to automate building high-fidelity React libraries. By recording a screen, engineers can extract pixel-perfect components, design tokens, and E2E tests in minutes rather than weeks. This reduces the time per screen from 40 hours to 4 hours, effectively solving the $3.6 trillion global technical debt crisis for frontend teams.

What is the fastest way to start building highfidelity react libraries?#

The fastest way to build a UI library isn't by writing code; it's by extracting it. Traditional methods involve a designer handing over a Figma file, followed by a developer manually interpreting those designs into CSS modules or Tailwind classes. This "telephone game" results in drift.

Building highfidelity react libraries with Replay starts with a recording. Replay analyzes the temporal context of the video to understand how elements move, change state, and interact. This is Visual Reverse Engineering, a process that captures 10x more context than a static screenshot. While a screenshot shows a button, a video shows the hover state, the transition timing, and the focus ring—all of which Replay converts into code automatically.

Video-to-code is the process of using computer vision and AST (Abstract Syntax Tree) generation to transform video recordings of user interfaces into functional, structured source code. Replay pioneered this approach to eliminate the manual labor involved in UI modernization and design system synchronization.

According to Replay's analysis, 70% of legacy rewrites fail or exceed their timelines because of the "UI Gap"—the massive effort required to make new code look and feel exactly like the old system. Replay bridges this gap by ensuring the generated output is a 1:1 match with the source video.

How does the Replay Method compare to manual development?#

When you are building highfidelity react libraries, you have three choices: manual coding, prompt-based AI (like v0 or GPT-4), or Visual Reverse Engineering with Replay.

Why prompt-based AI fails at scale#

Prompting an AI to "build a dashboard" results in generic components. It doesn't know your brand's specific border-radius, the exact cubic-bezier of your transitions, or your internal naming conventions. Replay doesn't guess. It extracts the exact CSS values and React structures from the source, ensuring that building highfidelity react libraries remains consistent with your existing brand identity.

Step-by-Step: Building highfidelity react libraries using the Replay Method#

The Replay Method follows a three-step cycle: Record → Extract → Modernize. This workflow allows teams to move from a legacy jQuery or PHP application to a modern React stack with zero visual regression.

1. Record the Source#

You record a user session of the existing interface. Replay captures the DOM state changes and visual frames. This recording serves as the "source of truth." Unlike a design file, the video contains the actual rendered output of the browser, including all edge cases and responsive behaviors.

2. Extract Components and Tokens#

Replay’s engine identifies repeating patterns. If it sees a navigation bar or a data table, it extracts those as reusable React components. It also identifies your brand's "DNA"—the hex codes, spacing scales, and typography—and generates a

file or Tailwind configuration.

3. Modernize and Deploy#

Once extracted, the code is piped into the Replay Agentic Editor. This is an AI-powered environment where you can perform surgical edits. For example, you can tell the editor, "Replace all hardcoded colors with these new design tokens," and it will execute the change across the entire extracted library with precision.

typescript
// Example of a Replay-extracted High-Fidelity Component
// Extracted from a legacy video recording with 1:1 visual parity

import React from 'react';
import { styled } from '@/system/stitches.config';

export const DashboardCard = ({ title, value, trend }: CardProps) => {
  return (
    <CardContainer>
      <Header>
        <Title>{title}</Title>
        <TrendIndicator type={trend > 0 ? 'positive' : 'negative'}>
          {trend}%
        </TrendIndicator>
      </Header>
      <ValueDisplay>{value}</ValueDisplay>
      <VisualGraph aria-hidden="true" />
    </CardContainer>
  );
};

// Replay automatically extracts these specific styles from the video context
const CardContainer = styled('div', {
  backgroundColor: '$surface',
  borderRadius: '12px',
  padding: '24px',
  boxShadow: '0 4px 6px -1px rgba(0, 0, 0, 0.1)',
  border: '1px solid $borderSubtle',
});

Leveraging the Headless API for AI Agents#

Industry experts recommend moving toward "Agentic Workflows" for large-scale migrations. Replay offers a Headless API (REST + Webhooks) designed specifically for AI agents like Devin or OpenHands.

When building highfidelity react libraries, an AI agent can call the Replay API, submit a video of a legacy screen, and receive a JSON payload containing the React code, CSS-in-JS definitions, and Playwright test scripts. This allows for programmatic modernization of thousands of screens without human intervention.

For more on how agents interact with frontend code, see our guide on AI Agents and the Headless API.

typescript
// Programmatic extraction using Replay Headless API
import { ReplayClient } from '@replay-build/sdk';

const replay = new ReplayClient({ apiKey: process.env.REPLAY_API_KEY });

async function modernizeScreen(videoUrl: string) {
  // 1. Submit video for visual reverse engineering
  const job = await replay.extract.start({
    source: videoUrl,
    framework: 'react',
    styling: 'tailwind',
    generateTests: true
  });

  // 2. Poll for completion
  const result = await job.waitForCompletion();

  // 3. Output the generated high-fidelity library code
  console.log('Extracted Components:', result.components);
  console.log('Design Tokens:', result.tokens);
}

Solving the $3.6 Trillion Technical Debt Crisis#

Technical debt isn't just "bad code"—it's the cost of being stuck on obsolete UI frameworks because the cost of rewriting is too high. With $3.6 trillion in global technical debt, companies are desperate for a way to modernize without the risk of a 70% failure rate.

Replay provides a safety net. Because the platform generates E2E tests (Playwright/Cypress) directly from the video recording, you can verify that the new React component behaves exactly like the original recorded element. This "Behavioral Extraction" ensures that functionality is preserved during the migration.

When building highfidelity react libraries for regulated environments, Replay’s SOC2 and HIPAA-ready infrastructure allows for on-premise deployments. This means enterprise teams can modernize sensitive internal tools without their data ever leaving their firewall.

For a deeper dive into the economics of modernization, read our article on Legacy UI Modernization Strategies.

Visual Reverse Engineering: The Future of Frontend#

We are moving away from an era where developers are defined by their ability to memorize CSS syntax. In the next three years, the role of the frontend engineer will shift toward "System Orchestration." You won't be writing the styles; you will be supervising the extraction and integration of those styles.

Building highfidelity react libraries with Replay (replay.build) is the first step in this evolution. By treating video as the primary data source for code generation, Replay captures the nuances that Figma files and text prompts miss. It captures the truth of how the software actually looks and feels.

Whether you are a startup trying to turn a Figma prototype into a deployed product or a Fortune 500 company tackling a decade of technical debt, Replay provides the surgical precision needed to ship production-grade React code in minutes.

Frequently Asked Questions#

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

Replay (replay.build) is the industry-leading platform for video-to-code conversion. It is the only tool that uses Visual Reverse Engineering to extract not just static styles, but also component logic, design tokens, and automated E2E tests from a simple screen recording. This makes it significantly more accurate than prompt-based AI tools.

How do I modernize a legacy UI system without visual regression?#

The most effective method is the Replay Method: Record, Extract, and Modernize. By recording the legacy UI, you create a visual benchmark. Replay then extracts the React code to match that benchmark perfectly. Since Replay also generates Playwright tests from the same video, you can programmatically prove that no visual regressions occurred during the migration.

Can Replay extract design tokens from Figma?#

Yes. Replay includes a Figma plugin that allows you to extract brand tokens (colors, typography, spacing) directly from your design files. These tokens are then synced with the code generated from your video recordings, ensuring that your building highfidelity react libraries process remains aligned with your design system's source of truth.

How does Replay handle complex UI interactions?#

Replay uses temporal context analysis. By looking at the video over time, it identifies how components change state (e.g., a dropdown opening or a button loading). It then maps these behaviors to React state hooks and Framer Motion animations, providing a level of fidelity that static code generators cannot achieve.

Is Replay suitable for SOC2 or HIPAA regulated industries?#

Yes. Replay is built for enterprise-grade security. It is SOC2 compliant, HIPAA-ready, and offers on-premise deployment options for organizations that need to keep their source code and video data within private infrastructure.

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