downlink/docs/features.md

Features Documentation

Current Features

1. YouTube Video Information Retrieval

• Fetch video metadata without downloading
• Display video title, thumbnail, and duration
• View available formats

Implementation: app/api/info endpoint

2. Video Download

• Download videos in multiple formats:
  • MP4 (most compatible)
  • WebM (web-optimized)
  • MKV (high quality)
  • AVI (legacy support)

Implementation: app/api/download endpoint with formatType: "video"

3. Audio Extraction

• Extract audio from videos in multiple formats:
  • MP3 (most compatible, compressed)
  • WAV (uncompressed, high quality)
  • M4A (Apple format)
  • Opus (modern, efficient)

Implementation: app/api/download endpoint with formatType: "audio"

4. Format Transcoding

• Automatic format conversion using yt-dlp and ffmpeg
• Best quality selection for requested format
• Audio extraction and conversion for audio formats

Implementation: Server-side processing in lib/youtube.ts

5. Modern UI

• Responsive design with Tailwind CSS
• shadcn/ui components for consistent styling
• Loading states and error handling
• Video thumbnail preview
• Format selection dropdowns

Implementation: app/page.tsx with shadcn/ui components

6. URL Validation

• Client-side and server-side URL validation
• Support for various YouTube URL formats:
  • https://www.youtube.com/watch?v=...
  • https://youtu.be/...
  • youtube.com/watch?v=...

Implementation: lib/utils.ts - isValidYouTubeUrl()

7. Safe File Handling

• Filename sanitization to prevent directory traversal
• Unique file IDs to prevent conflicts
• Proper file extension handling

Implementation: lib/youtube.ts - sanitizeFilename()

Feature Roadmap

Planned Features

Short Term

• Download progress tracking
• File size display before download
• Video quality selection (720p, 1080p, etc.)
• Download history
• Error recovery and retry mechanism

Medium Term

• Playlist support
• Batch downloads
• Custom ffmpeg parameters
• Download queue management
• File cleanup automation

Long Term

• User authentication
• Download quotas and limits
• Cloud storage integration (S3, etc.)
• API rate limiting
• Webhook notifications
• Mobile app support

Feature Usage Examples

Download MP4 Video

const response = await fetch('/api/download', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    url: 'https://www.youtube.com/watch?v=...',
    format: 'mp4',
    formatType: 'video'
  })
});

Extract MP3 Audio

const response = await fetch('/api/download', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    url: 'https://www.youtube.com/watch?v=...',
    format: 'mp3',
    formatType: 'audio'
  })
});

Get Video Info

const response = await fetch('/api/info', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    url: 'https://www.youtube.com/watch?v=...'
  })
});

Feature Limitations

Current Limitations

1. No Progress Tracking: Users cannot see download progress
2. No File Size Limits: Large files may cause issues
3. No Cleanup: Files accumulate in storage
4. Single Format: One format per download request
5. No Playlist Support: Only single videos
6. No Quality Selection: Downloads best available quality
7. No Authentication: No user accounts or history

Known Issues

• Large files may timeout on slow connections
• Some videos may not be available in requested format
• Audio conversion (MP3/WAV) requires ffmpeg
• No validation of available formats before download

Feature Dependencies

Required System Tools

• yt-dlp: For video downloading and format selection
• ffmpeg: For audio format conversion (MP3, WAV)

Required npm Packages

• Next.js 16+
• React 19+
• shadcn/ui components
• Tailwind CSS
• Lucide React (icons)

Feature Testing

Manual Testing Checklist

• Enter valid YouTube URL and get info
• Download video in MP4 format
• Download video in WebM format
• Extract audio as MP3
• Extract audio as WAV
• Test with invalid URL (should show error)
• Test with missing format (should show error)
• Verify file downloads correctly
• Check filename sanitization

Automated Testing (Future)

• Unit tests for utility functions
• Integration tests for API endpoints
• E2E tests for user flows
• Format validation tests