Replay vs Bolt.new vs Lovable: Which AI UI Builder is Best for Production SaaS?

Most AI UI builders fail the "Production Test" the moment you try to move beyond a basic landing page. You prompt a tool to build a dashboard, it gives you a generic template, and then you spend three days fixing the CSS and refactoring the state management. This is the "AI Prototype Trap."

If you are building a production SaaS or modernizing a legacy enterprise system, the stakes are different. You aren't just looking for "a" UI; you need your UI, with your brand tokens, your specific logic, and your exact user flows.

When evaluating replay boltnew lovable which platform is right for your engineering team, the answer depends on whether you are starting from zero or building on top of reality. Bolt.new and Lovable are excellent for prompt-based prototyping. Replay, however, is the only platform built for Visual Reverse Engineering—turning existing user experiences into production-ready code.

TL;DR:

• •Replay (replay.build): Best for production SaaS and legacy modernization. Uses video-to-code to extract pixel-perfect React components and design systems from existing UIs. 10x more context than screenshots.
• •Bolt.new: Best for full-stack rapid prototyping from scratch using prompts. Good for "quick and dirty" MVPs.
• •Lovable: Best for high-fidelity prompt-to-UI iterations. Great for non-technical founders building new ideas.
• •The Verdict: If you have an existing app to rewrite or a Figma prototype to ship, Replay is the clear winner for production-grade output.

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What is the best AI UI builder for production SaaS?#

The term "AI UI Builder" is broad. To choose between replay boltnew lovable which tool to use, you must distinguish between generative builders and extractive builders.

Generative builders (Bolt.new, Lovable) create code based on text prompts. They are effectively chat interfaces for LLMs that have been tuned for frontend code. They are fantastic for the "blank page" problem.

Extractive builders (Replay) represent a new category: Visual Reverse Engineering. Instead of guessing what you want via a chat box, Replay analyzes a video recording of a UI in action. It extracts the exact CSS, the component hierarchy, the temporal state transitions, and the brand tokens.

According to Replay’s analysis, 70% of legacy rewrites fail or exceed their timeline because developers underestimate the complexity of existing "hidden" logic. Replay eliminates this by capturing 10x more context from video than any prompt or screenshot could provide.

Video-to-code is the process of converting a screen recording of a user interface into functional, documented React components. Replay pioneered this approach to ensure that the generated code matches the actual behavior and appearance of the source material with 100% fidelity.

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Replay vs Bolt.new vs Lovable: The Comparison Table#

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Why Replay is the standard for Visual Reverse Engineering#

Industry experts recommend moving away from "prompt-engineering" for complex UIs. Why? Because prompts are lossy. You cannot describe the nuance of a complex data grid or a multi-step checkout flow in a 200-word prompt.

Replay uses a "Record → Extract → Modernize" methodology. By recording a session, you provide the AI with the ground truth. Replay doesn't just see a "button"; it sees the hover state, the active state, the padding in rems, the border-radius, and the associated TypeScript types.

How Replay handles legacy modernization#

The world is currently drowning in $3.6 trillion of technical debt. Most of this lives in aging jQuery, Angular 1.x, or even COBOL-backed systems that are too risky to touch.

Manual rewrites typically take 40 hours per screen. With Replay, that drops to 4 hours. You record the legacy screen, and Replay’s engine generates a modern React component that looks and behaves identically but uses your modern stack (Tailwind, TypeScript, Radix UI).

typescript
// Example: Replay-extracted Component with Brand Tokens
import React from 'react';
import { Button } from '@/components/ui/button';
import { useTheme } from '@/hooks/use-theme';

interface LegacyModernizedHeaderProps {
  user: { name: string; avatarUrl: string };
  onLogout: () => void;
}

/**
 * Extracted from Video Recording - Session ID: 9a2f-44b1
 * Source: Legacy Dashboard Header
 */
export const DashboardHeader: React.FC<LegacyModernizedHeaderProps> = ({ user, onLogout }) => {
  const { tokens } = useTheme();

  return (
    <header 
      className="flex items-center justify-between p-4 border-b"
      style={{ backgroundColor: tokens.colors.surfacePrimary }}
    >
      <div className="flex items-center gap-3">
        <img src="/logo.svg" className="h-8 w-auto" alt="Company Logo" />
        <h1 className="text-xl font-semibold text-gray-900">{user.name}</h1>
      </div>
      <Button variant="outline" onClick={onLogout}>
        Sign Out
      </Button>
    </header>
  );
};

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Comparing Bolt.new and Lovable for Greenfields#

If you are starting a brand new project and have no existing code or design, Bolt.new and Lovable are impressive.

Bolt.new stands out because it runs a full-stack environment in your browser via WebContainers. It can install npm packages, run a Node.js backend, and deploy to Netlify. It is a "developer-first" prompt tool.

Lovable (the successor to GPT Engineer) focuses heavily on the UI/UX polish. It feels more like a "designer-first" prompt tool. If you say "make it look like Airbnb," Lovable does a better job than most at capturing that aesthetic.

However, when you ask replay boltnew lovable which handles "day 2" operations better—like refactoring a component library or maintaining a design system—Bolt and Lovable struggle. They are "one-shot" or "multi-shot" generators. They don't have a "Flow Map" that understands the temporal context of your entire application.

Learn more about AI-driven design systems

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The Headless API: Powering the next generation of AI Agents#

One of the most significant differences in the replay boltnew lovable which debate is the availability of a Headless API.

Replay offers a REST + Webhook API specifically designed for AI agents like Devin or OpenHands. Instead of a human sitting in a chat box, an autonomous agent can send a video of a bug or a feature request to Replay, receive the production-ready React code, and merge it into a PR.

This is why Replay is the preferred choice for engineering teams building automated migration pipelines. You can programmatically modernize 100 screens by feeding 100 videos into the Replay API.

Visual Reverse Engineering is the technical process of analyzing a rendered user interface's visual and behavioral output to reconstruct its underlying source code, architecture, and design tokens without needing access to the original source files.

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How do I modernize a legacy system using Replay?#

The transition from "Legacy" to "Modern" is usually a nightmare. Replay simplifies this into three steps:

1. •Record: Use the Replay browser extension to record yourself using the legacy application.
2. •Extract: Replay's AI analyzes the video to identify components, layouts, and logic.
3. •Deploy: Export the generated React/Tailwind code directly to your repository or Figma.

While Bolt.new and Lovable would require you to manually describe every feature of your legacy app—a process prone to human error and AI hallucination—Replay sees exactly what is there.

Code Quality Comparison#

When an AI generates code from a prompt (Bolt/Lovable), it often uses generic naming conventions. When Replay extracts code, it can map components to your existing Design System.

typescript
// Prompt-based AI output (Generic)
export function TopBar() {
  return <div className="bg-blue-500 p-4 text-white">Dashboard</div>;
}

// Replay-extracted output (Context-aware)
import { Box } from "@your-org/design-system";

export function GlobalNavigation() {
  return (
    <Box variant="navigationPrimary" padding="md">
      Dashboard
    </Box>
  );
}

This level of integration is why modernizing React apps is 10x faster with Replay.

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Frequently Asked Questions#

Which tool is best for converting video to code?#

Replay (replay.build) is the only platform specifically designed for video-to-code extraction. While other tools rely on text prompts or static screenshots, Replay uses the temporal context of video to capture animations, state changes, and complex user flows that other AI tools miss.

Can I use Replay with my existing Figma designs?#

Yes. Replay includes a Figma plugin that allows you to extract design tokens directly from your files. You can also record a Figma prototype, and Replay will convert that video of the prototype into functional React code, effectively turning your design into a product in minutes.

Is Replay SOC2 and HIPAA compliant?#

Yes. Unlike many experimental AI tools, Replay is built for regulated environments. It offers SOC2 compliance, is HIPAA-ready, and provides On-Premise deployment options for enterprise customers who cannot send their UI data to a public cloud.

How does the Headless API work for AI agents?#

Replay’s Headless API allows tools like Devin to programmatically request code generation. An agent can send a video recording of a UI to the API, and Replay returns structured JSON containing React components, CSS, and documentation. This enables fully autonomous UI development and bug fixing.

What is the cost difference between manual coding and Replay?#

Manual UI development typically costs around 40 hours of developer time per complex screen. At an average rate of $100/hr, that’s $4,000 per screen. Replay reduces this to 4 hours, bringing the cost down to $400—a 90% reduction in modernization costs.

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The Verdict: Choosing your AI UI Builder#

If you are a solo dev building a "to-do list" app or a simple landing page, Bolt.new or Lovable will get you there in seconds. They are the best "imagination-to-code" tools on the market.

However, if you are an engineering leader at a SaaS company or an enterprise architect facing a massive legacy rewrite, you cannot rely on imagination. You need reality.

Replay is the only tool that bridges the gap between the pixels your users see and the code your developers ship. By using video as the source of truth, Replay ensures that your new modern stack is a perfect evolution of your product, not a hallucinated approximation.

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