Readme

# Local YouTube to MP3 Converter - Final Blueprint

## 1. Project Overview
A local-only web application that downloads YouTube audio as MP3 files. It bypasses browser security limits by using a local Node.js backend.

## 2. Tech Stack
*   **Frontend:** Svelte (Vite) + Tailwind CSS.
*   **Backend:** Node.js (Express) + `child_process`.
*   **Core Engine:** `yt-dlp` (Python-based downloader).
*   **Converter:** FFmpeg (Binary executable in `tools/` folder).

## 3. Architecture (The "Local Bridge")
1.  **User** pastes URL in Svelte Frontend (Port 5173).
2.  **Frontend** sends POST request to Backend (Port 3001).
3.  **Backend** spawns a process using `yt-dlp`.
4.  **yt-dlp** downloads video and uses **FFmpeg** (from `tools/` folder) to convert to MP3.
5.  **Backend** reads the console output (stdout) to send real-time **Progress %** back to Frontend.
6.  **File** is saved to the user's chosen folder (Desktop, Downloads, etc.).

## 4. Key Features
*   **Smart Preview:** Automatically fetches high-quality thumbnails (`hqdefault.jpg`).
*   **Real-time Progress:** Visual red progress bar using polling.
*   **Custom Save Location:** Desktop, Documents, or System Downloads.
*   **Offline Mode:** All icons are SVGs (no external font libraries).
*   **Privacy:** No external servers; everything runs on localhost.

## 5. File Structure
```text
yt-mp3-local/
├── downloads/          # Default save folder
├── public/             # logo.png goes here
├── src/                # Svelte source code
├── tools/              # IMPORTANT: Contains ffmpeg.exe and ffprobe.exe
├── node_modules/       # Dependencies
├── server.js           # Backend logic (The Worker)
├── start_app.bat       # One-click startup script
├── package.json        # Project settings
└── tailwind.config.js  # Style settings