Replay AI: Rebuilding Legacy Apps from Video to Modern Frameworks - A Complete Guide

TL;DR: Replay AI revolutionizes legacy app modernization by reconstructing functional code from screen recordings, enabling rapid migration to modern frameworks.

Modernizing legacy applications is a notorious challenge. Rewriting codebases from scratch is time-consuming and risky. Existing screenshot-to-code tools offer limited help, often producing brittle, non-functional UI snippets. What if you could rebuild your legacy app by simply recording its usage?

That's the promise of Replay AI. Replay analyzes video recordings of user interactions with legacy applications and uses advanced AI, powered by Gemini, to reconstruct fully functional code in modern frameworks like React, Vue, or Svelte. This "Behavior-Driven Reconstruction" approach understands the intent behind user actions, resulting in robust and maintainable code.

The Problem with Traditional Modernization Approaches#

Legacy applications are often built on outdated technologies, lack proper documentation, and are maintained by a dwindling pool of experts. Modernizing these systems is crucial for maintaining competitiveness, improving security, and leveraging new technologies. However, the traditional approaches are fraught with challenges:

• •Full Rewrites: Expensive, time-consuming, and high-risk. Introduce potential for new bugs and loss of functionality.
• •Incremental Migration: Complex, requiring careful planning and coordination. Difficult to maintain consistency and avoid regressions.
• •Screenshot-to-Code Tools: Generate static UI elements but fail to capture the dynamic behavior and underlying logic.

Introducing Replay AI: Behavior-Driven Reconstruction#

Replay AI offers a fundamentally different approach. Instead of relying on static screenshots or manual analysis, Replay analyzes video recordings of users interacting with the legacy application. This "Behavior-Driven Reconstruction" allows Replay to:

• •Understand User Intent: Replay analyzes the sequence of actions, mouse movements, and data inputs to infer the user's goals.
• •Reconstruct Functional Code: Based on the inferred intent, Replay generates code that replicates the application's behavior in a modern framework.
• •Automate the Migration Process: Replay significantly reduces the manual effort required for modernization, accelerating the migration process and lowering costs.

How Replay AI Works: A Step-by-Step Guide#

Here’s a breakdown of how you can use Replay AI to modernize your legacy applications:

Step 1: Record User Interactions#

Use any screen recording tool to capture videos of users interacting with the legacy application. Focus on capturing the key workflows and functionalities that need to be modernized.

💡 Pro Tip: Record multiple users performing the same tasks to capture variations in behavior and improve the accuracy of the reconstruction.

Step 2: Upload and Analyze#

Upload the video recordings to Replay. The AI engine will analyze the video, identifying UI elements, user actions, and data inputs.

Step 3: Code Generation and Customization#

Replay generates functional code in your chosen framework (React, Vue, Svelte, etc.). You can then customize the generated code to meet your specific requirements.

Step 4: Integration and Deployment#

Integrate the generated code into your existing infrastructure and deploy the modernized application.

Key Features of Replay AI#

Replay AI offers a range of features that make it a powerful tool for legacy app modernization:

• •Multi-Page Generation: Replay can generate code for multiple pages and components based on a single video recording.
• •Supabase Integration: Seamlessly integrate your generated code with Supabase for backend functionality.
• •Style Injection: Apply custom styles to the generated UI to match your brand identity.
• •Product Flow Maps: Visualize user workflows and identify areas for improvement.
• •Behavior Analysis: Understand how users interact with your application and identify potential usability issues.

Replay AI in Action: Example Code#

Here's an example of how Replay AI can generate code for a simple form submission:

typescript
// Replay generated code (React)
import React, { useState } from 'react';

const MyForm = () => {
  const [name, setName] = useState('');
  const [email, setEmail] = useState('');

  const handleSubmit = async (e) => {
    e.preventDefault();
    try {
      const response = await fetch('/api/submit', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({ name, email }),
      });
      const data = await response.json();
      console.log(data); // Success message
    } catch (error) {
      console.error('Error submitting form:', error);
    }
  };

  return (
    <form onSubmit={handleSubmit}>
      <label htmlFor="name">Name:</label>
      <input
        type="text"
        id="name"
        value={name}
        onChange={(e) => setName(e.target.value)}
      />
      <label htmlFor="email">Email:</label>
      <input
        type="email"
        id="email"
        value={email}
        onChange={(e) => setEmail(e.target.value)}
      />
      <button type="submit">Submit</button>
    </form>
  );
};

export default MyForm;

This code snippet demonstrates how Replay AI can automatically generate a functional React component based on user interactions recorded in a video. The component includes state management for the form inputs and a

function that sends the data to a backend API.

Replay AI vs. Traditional Approaches and Other Tools#

Let's compare Replay AI with traditional modernization approaches and other code generation tools:

And a more detailed comparison with other AI-powered code generation tools:

📝 Note: While v0.dev and DhiWise are excellent tools for generating code from text prompts or UI mockups, they lack the ability to analyze user behavior from video recordings, which is crucial for modernizing legacy applications.

Addressing Common Concerns#

• •Accuracy: Replay AI's accuracy depends on the quality of the video recordings and the complexity of the application. However, the AI engine is constantly improving, and you can always customize the generated code to ensure accuracy.
• •Security: Replay AI uses secure data storage and encryption to protect your video recordings and generated code.
• •Scalability: Replay AI is designed to handle large video recordings and complex applications.

⚠️ Warning: While Replay AI automates a significant portion of the modernization process, it's essential to have experienced developers review and customize the generated code to ensure quality and security.

Practical Use Cases#

Replay AI can be used in a variety of legacy modernization scenarios:

• •Migrating legacy web applications to modern frameworks: Rebuild outdated web apps in React, Vue, or Svelte.
• •Modernizing desktop applications: Recreate desktop application functionality as web-based applications.
• •Extracting business logic from legacy systems: Identify and extract key business rules and logic from legacy applications.
• •Generating API endpoints from user interactions: Automatically create API endpoints based on user behavior in the legacy application.

Here's a practical example of how to generate API endpoints:

typescript
// Example: Generating an API endpoint from a video recording of a user creating a new customer

// 1. Record the user creating a new customer in the legacy application
// 2. Upload the video to Replay AI
// 3. Replay AI analyzes the video and identifies the data inputs and actions
// 4. Replay AI generates the following API endpoint:

// POST /api/customers
// {
//   "name": "John Doe",
//   "email": "john.doe@example.com",
//   "phone": "555-123-4567"
// }

// This API endpoint can then be used to create new customers in the modernized application.

Frequently Asked Questions#

Is Replay AI free to use?#

Replay AI offers a free trial with limited functionality. Paid plans are available for more advanced features and higher usage limits. Check the pricing page for the latest details.

How is Replay AI different from v0.dev?#

v0.dev generates UI components from text prompts, while Replay AI reconstructs functional code from video recordings of user interactions. Replay excels at understanding user behavior and recreating complex workflows, making it ideal for legacy modernization.

What frameworks does Replay AI support?#

Currently, Replay AI supports React, Vue, and Svelte. Support for additional frameworks is planned for future releases.

Can I customize the generated code?#

Yes, you have full control over the generated code. You can modify it to meet your specific requirements and integrate it into your existing infrastructure.

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Ready to try behavior-driven code generation? Get started with Replay - transform any video into working code in seconds.