How to Convert UI Video to a Full-Stack SvelteKit App With Supabase and Replay AI

TL;DR: Convert UI videos into a fully functional SvelteKit application with Supabase integration using Replay's behavior-driven reconstruction, bypassing limitations of screenshot-based tools.

The "screenshot-to-code" promise has always been tantalizing, but the reality is often disappointing. Static images lack the critical context of user behavior – the "why" behind the UI. What good is a pretty picture of a button if you don't know what it's supposed to do? You end up spending more time debugging and wiring up functionality than you save.

Replay changes that. By analyzing video, not just screenshots, Replay reconstructs working UI from screen recordings, understanding user intent through "Behavior-Driven Reconstruction." This isn't just about pixels; it's about understanding workflows. And with direct Supabase integration and SvelteKit support, you can rapidly prototype and deploy full-stack applications.

Why Video-to-Code is the Future#

Traditional screenshot-to-code tools treat UI as a static artifact. They can generate HTML and CSS, but they fail to capture the dynamic interactions that define a modern web application. This results in:

• •Missing Functionality: Buttons don't click, forms don't submit, and animations are absent.
• •Contextual Blindness: The tool doesn't understand the purpose of different UI elements within a larger flow.
• •Limited Scalability: Manually wiring up the generated code becomes a bottleneck as the application grows.

Replay addresses these limitations by analyzing video, allowing it to:

• •Infer User Intent: Understand the purpose of each UI element based on user interactions.
• •Reconstruct Application Logic: Generate code that accurately reflects the intended behavior of the UI.
• •Automate Integration: Seamlessly connect the generated code to backend services like Supabase.

Building a SvelteKit App with Supabase and Replay: A Step-by-Step Guide#

Let's walk through the process of converting a UI video into a functional SvelteKit application with Supabase integration using Replay.

Step 1: Capture the UI Video#

Record a video demonstrating the desired user flow. Be clear and deliberate in your interactions. For example, if you're building a to-do list app, record yourself:

1. •Adding a new task.
2. •Marking a task as complete.
3. •Deleting a task.

The more detail you provide in the video, the better Replay can understand the intended behavior.

💡 Pro Tip: Speak clearly while recording, describing the actions you're taking. This provides additional context for Replay's AI.

Step 2: Upload the Video to Replay#

Upload your recorded video to the Replay platform. Replay will analyze the video and generate a working SvelteKit codebase. This process involves:

1. •Frame-by-Frame Analysis: Replay analyzes each frame of the video to identify UI elements.
2. •Behavioral Inference: Replay infers the purpose of each UI element based on user interactions.
3. •Code Generation: Replay generates SvelteKit components, routes, and API endpoints.

Step 3: Configure Supabase Integration#

Replay allows you to seamlessly integrate your SvelteKit application with Supabase. To configure the integration:

1. •Provide Supabase Credentials: Enter your Supabase project URL and API key in the Replay settings.
2. •Define Data Models: Specify the data models for your application (e.g.,
   text

   todos
   ,
   text

   users
   ). Replay will automatically generate the necessary database schemas and API endpoints.

Step 4: Review and Customize the Generated Code#

Once Replay has generated the code, review it carefully. You may need to make minor adjustments to:

• •Styling: Fine-tune the CSS to match your desired aesthetic. Replay supports style injection, allowing you to easily override default styles.
• •Logic: Add any custom logic that Replay couldn't infer from the video.
• •Data Validation: Implement data validation to ensure the integrity of your Supabase database.

Here's an example of a generated SvelteKit component for displaying a to-do list:

svelte
<!-- src/lib/components/TodoList.svelte -->
<script>
  import { onMount } from 'svelte';
  import { supabase } from '$lib/supabaseClient';

  let todos = [];

  onMount(async () => {
    const { data, error } = await supabase
      .from('todos')
      .select('*')
      .order('created_at', { ascending: false });

    if (error) {
      console.error('Error fetching todos:', error);
      return;
    }

    todos = data;
  });

  async function toggleComplete(id, completed) {
    const { error } = await supabase
      .from('todos')
      .update({ completed: !completed })
      .eq('id', id);

    if (error) {
      console.error('Error updating todo:', error);
      return;
    }

    todos = todos.map(todo =>
      todo.id === id ? { ...todo, completed: !completed } : todo
    );
    todos = [...todos]; // Trigger reactivity
  }

  async function deleteTodo(id) {
    const { error } = await supabase
      .from('todos')
      .delete()
      .eq('id', id);

    if (error) {
      console.error('Error deleting todo:', error);
      return;
    }

    todos = todos.filter(todo => todo.id !== id);
    todos = [...todos]; // Trigger reactivity
  }
</script>

<ul>
  {#each todos as todo (todo.id)}
    <li>
      <input type="checkbox" checked={todo.completed} on:click={() => toggleComplete(todo.id, todo.completed)}>
      <span class:completed={todo.completed}>{todo.text}</span>
      <button on:click={() => deleteTodo(todo.id)}>Delete</button>
    </li>
  {/each}
</ul>

<style>
  .completed {
    text-decoration: line-through;
    color: gray;
  }
</style>

And here's an example of a generated API endpoint for adding a new to-do item:

typescript
// src/routes/api/todos/+server.ts
import { supabase } from '$lib/supabaseClient';
import { json } from '@sveltejs/kit';
import type { RequestHandler } from './$types';

export const POST: RequestHandler = async ({ request }) => {
  const { text } = await request.json();

  if (!text) {
    return json({ error: 'Text is required' }, { status: 400 });
  }

  const { data, error } = await supabase
    .from('todos')
    .insert([{ text }])
    .select();

  if (error) {
    console.error('Error creating todo:', error);
    return json({ error: error.message }, { status: 500 });
  }

  return json(data[0], { status: 201 });
};

Step 5: Deploy to Production#

Once you're satisfied with the generated code, deploy your SvelteKit application to a hosting provider like Vercel or Netlify.

📝 Note: Replay automatically generates a "Product Flow Map" visualizing the user journey captured in the video, making it easy to understand and maintain the application's structure.

Replay vs. Traditional Development: A Paradigm Shift#

Replay isn't just another code generation tool; it represents a fundamental shift in how we approach UI development. By leveraging video as the source of truth, Replay enables:

• •Faster Prototyping: Quickly generate working prototypes from screen recordings.
• •Reduced Development Time: Automate the tedious task of manually coding UI components.
• •Improved Collaboration: Share UI videos with designers and developers to facilitate better communication and understanding.
• •Enhanced Maintainability: The Product Flow Map provides a clear and visual representation of the application's structure, making it easier to maintain and update.

⚠️ Warning: While Replay significantly accelerates development, it's not a replacement for skilled developers. You'll still need to review and customize the generated code to ensure it meets your specific requirements.

Frequently Asked Questions#

Is Replay free to use?#

Replay offers a free tier with limited features and usage. Paid plans are available for more advanced features and higher usage limits. Check the Replay website for the most up-to-date pricing information.

How is Replay different from v0.dev?#

While both tools aim to generate code from visual inputs, Replay distinguishes itself by using video as the primary input, enabling it to understand user behavior and reconstruct application logic more accurately. v0.dev primarily relies on text prompts and UI descriptions, which can be less precise and require more manual refinement. Replay's behavior-driven reconstruction offers a more complete and functional starting point.

What types of applications can I build with Replay?#

Replay is suitable for building a wide range of UI-driven applications, including:

• •Web applications
• •Mobile applications
• •Desktop applications
• •Prototypes
• •Internal tools
• •Landing pages

The key requirement is that you can capture a video demonstrating the desired user flow.

What if the generated code isn't perfect?#

Replay is designed to generate a solid foundation for your application. However, you'll likely need to make some adjustments to the generated code to fine-tune the styling, logic, and data validation. Replay's style injection feature makes it easy to customize the CSS, and you can always modify the generated code directly to add custom logic.

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