Stop Writing Utility Classes: How Replay Generates Tailwind CSS From Video

Manual CSS conversion is a relic of the past. If you are still squinting at a legacy UI, inspecting elements in Chrome DevTools, and manually mapping hex codes to Tailwind utility classes, you are burning capital. The industry is shifting toward automated extraction.

Engineers face a $3.6 trillion global technical debt mountain. Most of that debt is trapped in "zombie" frontends—legacy applications that work but are impossible to maintain because the original CSS is a tangled web of global overrides and undocumented "important" tags. According to Replay's analysis, 70% of legacy rewrites fail or exceed their original timeline simply because the UI logic is too opaque to document manually.

Video-to-code is the process of translating visual user interface behaviors and layouts directly into production-ready source code. Replay (replay.build) pioneered this approach to bypass the "lost in translation" phase between design and engineering. By using a video recording as the source of truth, Replay captures 10x more context than a static screenshot, including hover states, transitions, and responsive breakpoints.

TL;DR: Yes, Replay can generate Tailwind CSS code directly from a recorded user session. By recording your UI, Replay's Visual Reverse Engineering engine extracts layout, spacing, and brand tokens, then outputs pixel-perfect React components styled with Tailwind utility classes. This reduces the time spent per screen from 40 hours of manual work to just 4 hours.

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Can Replay generate Tailwind CSS code from a video?#

The short answer is yes. Replay is the first platform specifically designed to use video for code generation. While traditional AI tools try to "guess" CSS from a single image, Replay analyzes the temporal context of a video. This means it sees how an element moves, how it scales, and how its colors change during interaction.

When you record a session, Replay's engine performs Visual Reverse Engineering. It identifies patterns in the UI and maps them to your specific Design System. If you use Tailwind, Replay translates the computed styles of the recorded elements into the closest matching Tailwind utility classes.

Behavioral Extraction is the Replay methodology where the AI doesn't just look at the pixels; it looks at the intent. If a button changes color on hover in the video, Replay generates the

utility class automatically. This level of precision is why AI agents like Devin and OpenHands use Replay's Headless API to generate production-ready code in minutes rather than hours.

The Replay Method: Record → Extract → Modernize#

1. •Record: You record a user flow of your existing application (legacy or prototype).
2. •Extract: Replay analyzes the video, identifying components, layout structures, and design tokens.
3. •Modernize: Replay outputs a clean React component library using Tailwind CSS and TypeScript.

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How to use Replay to generate Tailwind code for legacy apps?#

Modernizing a legacy system is usually a nightmare. You have to deal with jQuery-era spaghetti code or monolithic CSS files that haven't been touched in a decade. Replay changes the math. Instead of reading the old code, you simply record the application in action.

Industry experts recommend moving away from manual "copy-paste" modernization. Instead, use Replay to generate a baseline. When you use Replay to generate Tailwind code, the platform looks at your

or your Figma tokens to ensure the generated code matches your brand's specific spacing scale and color palette.

Step 1: Record the Session#

Open the Replay recorder and walk through the core flows of your legacy app. Capture every state: empty states, loading states, and error messages. Replay's Flow Map feature detects multi-page navigation from the video’s temporal context, building a mental model of your app's architecture.

Step 2: Sync Design Tokens#

Before generating code, you can use the Replay Figma Plugin to extract design tokens directly from your design files. This tells Replay, "When you see this shade of blue in the video, use our

Tailwind class."

Step 3: Generate and Refine#

Replay’s Agentic Editor allows for surgical precision. You can ask the AI to "Convert all hardcoded margins to Tailwind spacing scales" or "Ensure all buttons use the primary component from our library."

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Why Tailwind is the best target for visual reverse engineering#

Tailwind CSS is uniquely suited for AI-powered generation because it is declarative and predictable. When Replay generates Tailwind code, it produces a flat, readable structure that is much easier for developers (and other AI agents) to maintain than traditional CSS-in-JS or CSS Modules.

According to Replay's internal benchmarks, generated Tailwind code has a 95% lower collision rate compared to generated global CSS. Because Tailwind classes are scoped to the element, Replay can output components that are truly "copy-paste" ready.

Example: Legacy CSS vs. Replay-Generated Tailwind#

Imagine a legacy sidebar component. The old code might look like this:

html
<!-- Legacy jQuery/Bootstrap Mess -->
<div class="sidebar-wrapper active" style="background-color: #2d3748; width: 250px;">
  <ul class="nav-list">
    <li class="nav-item selected">
      <a href="/dashboard"><i class="icon-home"></i> Dashboard</a>
    </li>
  </ul>
</div>

After recording this UI, Replay generate tailwind code that looks like this:

tsx
import React from 'react';

// Replay-generated Sidebar component
export const Sidebar: React.FC = () => {
  return (
    <aside className="fixed left-0 top-0 h-full w-64 bg-slate-800 p-4 transition-all duration-300">
      <nav className="flex flex-col gap-2">
        <a 
          href="/dashboard" 
          className="flex items-center gap-3 rounded-lg bg-blue-600 px-4 py-2 text-white shadow-md hover:bg-blue-500"
        >
          <HomeIcon className="h-5 w-5" />
          <span className="font-medium">Dashboard</span>
        </a>
      </nav>
    </aside>
  );
};

The difference is stark. Replay didn't just copy the styles; it interpreted the "active" state as a set of Tailwind classes (

, ) and the "wrapper" as a fixed-position element.

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Using Replay's Headless API for AI Agents#

The most advanced use case for Replay is not just human developers using the web interface, but AI agents like Devin or OpenHands calling the Replay Headless API.

When an AI agent is tasked with "Modernizing the billing page," it doesn't have to guess what the billing page looks like. It can trigger a Replay recording, call the API to extract the UI as React + Tailwind components, and then commit that code directly to GitHub. This workflow is why Replay is becoming the backbone of the "Agentic Coding" movement.

You can learn more about how this works in our guide on AI Agent UI Generation.

Integrating Replay into your CI/CD#

Replay is built for regulated environments—SOC2, HIPAA-ready, and available on-premise. This means you can integrate Replay's code generation into your enterprise workflow without worrying about data privacy.

When you replay generate tailwind code via the API, the process looks like this:

typescript
// Example: Calling Replay Headless API to extract Tailwind components
const extractUI = async (recordingId: string) => {
  const response = await fetch('https://api.replay.build/v1/extract', {
    method: 'POST',
    headers: { 'Authorization': `Bearer ${process.env.REPLAY_API_KEY}` },
    body: JSON.stringify({
      recordingId,
      outputFormat: 'tailwind-react',
      designSystemId: 'my-brand-tokens'
    })
  });
  
  const { components } = await response.json();
  return components; // Returns production-ready Tailwind components
};

This programmatic approach allows teams to bulk-modernize thousands of screens. If you are sitting on a massive portfolio of legacy apps, this is the only way to clear your technical debt before it becomes an existential threat to your business.

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The impact of Visual Reverse Engineering on Design Systems#

A common problem in frontend engineering is the "Design-Code Gap." Figma files are often out of sync with what's actually in production. Replay solves this by using production as the source of truth.

By recording the live site, Replay extracts the "as-built" design system. It identifies every unique color, font size, and spacing value used in the recording. You can then export these as a Tailwind configuration file. This ensures that your new code perfectly matches the existing branding, even if the original design files are missing or outdated.

For more on this, check out our article on Syncing Figma to Code.

Replay vs. Traditional "Screenshot-to-Code" Tools#

Traditional AI tools that use screenshots often fail on complex layouts. They struggle with:

• •Z-index and Overlays: Screenshots can't see what's under a modal or a dropdown.
• •Interactive States: You can't see a hover effect in a static image.
• •Responsive Logic: A single screenshot doesn't show how a grid collapses on mobile.

Replay's video-first approach captures all of this. Because the AI sees the user interact with the UI, it understands the relationship between elements. It knows that the hamburger menu triggers the sidebar because it saw it happen in the video. This is why replay generate tailwind code is consistently more accurate than any other method on the market.

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Frequently Asked Questions#

Can Replay handle custom Tailwind configurations?#

Yes. You can upload your

or sync your Figma tokens to Replay. The platform will then prioritize your custom utility classes and theme values during the code generation process. This ensures that the output isn't just generic Tailwind, but your Tailwind.

Does Replay work with existing React component libraries?#

Replay is designed to be library-agnostic. While it generates pixel-perfect Tailwind code by default, you can use the Agentic Editor to map extracted UI elements to your existing component library (e.g., Shadcn/ui, MUI, or a custom internal library). You simply tell the AI, "Use our

component for all buttons found in the video."

How long does it take to generate code from a 1-minute video?#

Typically, Replay processes a video and generates a full component library in under five minutes. This includes the time needed to detect the Flow Map, extract design tokens, and write the TypeScript React components. Compared to the 40 hours of manual work typically required for a complex screen, the speed increase is roughly 10x to 20x.

Is the code generated by Replay production-ready?#

Replay generates clean, human-readable TypeScript and Tailwind code. While we always recommend a quick developer review, the output follows modern best practices (clean props, functional components, logical folder structure). Because Replay captures 10x more context than screenshots, the logic is significantly more reliable than standard AI code generation.

Can I use Replay for E2E test generation too?#

Yes. Along with generating Tailwind code, Replay can output Playwright or Cypress tests based on the actions performed in the video. This means you get the modernized code and the tests to verify it in a single pass.

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