Using Web Seeds - WebTorrent

Web seeds are HTTP/HTTPS servers that provide torrent content as a fallback or supplement to peer-to-peer downloads. They implement BEP19 and allow torrents to be downloaded even when no peers are available.

What are Web Seeds?

Web seeds provide several benefits:

Guaranteed availability: Content remains accessible even with no peers
Initial seeding: Helps bootstrap new torrents before peers arrive
Performance: HTTP servers can often provide faster downloads than peers
CDN integration: Use CDN infrastructure for torrent content
Hybrid delivery: Combine P2P and HTTP for optimal performance

WebTorrent automatically manages web seed connections and switches between P2P and HTTP sources based on availability and performance.

Adding Web Seeds to Torrents

When creating a torrent, you can specify HTTP/HTTPS URLs as web seeds:

Basic Web Seed

import WebTorrent from 'webtorrent'

const client = new WebTorrent()

client.seed('/path/to/file.mp4', {
  name: 'My Video',
  urlList: [
    'https://example.com/files/'
  ]
}, torrent => {
  console.log('Torrent created with web seed')
  console.log('Web seeds:', torrent.urlList)
})

Multiple Web Seeds

client.seed(files, {
  name: 'My Files',
  urlList: [
    'https://cdn1.example.com/files/',
    'https://cdn2.example.com/backup/',
    'https://mirror.example.org/torrents/'
  ]
}, torrent => {
  console.log('Added', torrent.urlList.length, 'web seeds')
})

Web Seed URL Format

The web seed URL should be a base path where files can be accessed:

// If your torrent contains: video.mp4
// Web seed URL: https://example.com/files/
// Full URL will be: https://example.com/files/video.mp4

client.seed('/path/to/video.mp4', {
  urlList: ['https://example.com/files/']
})

For torrents with multiple files:

// Torrent contains:
//   - folder/video1.mp4
//   - folder/video2.mp4
// Web seed URL: https://example.com/content/
// Full URLs will be:
//   - https://example.com/content/folder/video1.mp4
//   - https://example.com/content/folder/video2.mp4

client.seed('/path/to/folder', {
  urlList: ['https://example.com/content/']
})

Using Torrents with Web Seeds

When you download a torrent that has web seeds, WebTorrent automatically uses them:

const magnetURI = 'magnet:?xt=urn:btih:...&ws=https://example.com/files/'

client.add(magnetURI, torrent => {
  console.log('Web seeds available:', torrent.urlList)
  
  torrent.on('download', bytes => {
    console.log('Downloaded from P2P or web seeds')
  })
})

Checking Web Seed Status

client.add(magnetURI, torrent => {
  torrent.on('wire', (wire, addr) => {
    console.log('Connection type:', wire.type)
    // Types: 'webrtc', 'tcpIncoming', 'tcpOutgoing', 'webSeed'
    
    if (wire.type === 'webSeed') {
      console.log('Connected to web seed')
    }
  })
})

Adding Web Seeds to Existing Torrents

You can add web seeds dynamically to torrents you’re downloading:

client.add(magnetURI, torrent => {
  // Add a web seed after torrent is added
  torrent.addWebSeed('https://backup-server.com/files/')
  
  console.log('Web seeds:', torrent.urlList)
})

Add When No Peers Available

client.add(magnetURI, torrent => {
  torrent.on('noPeers', announceType => {
    console.log('No peers found, adding web seed')
    torrent.addWebSeed('https://fallback-server.com/files/')
  })
})

Configuring Web Seeds

Control web seed behavior with client options:

const client = new WebTorrent({
  webSeeds: true,        // Enable web seeds (default: true)
  maxWebConns: 4         // Max simultaneous web seed connections per torrent
})

Or per-torrent:

client.add(magnetURI, {
  maxWebConns: 8,        // More connections = faster from web seeds
  urlList: [             // Add additional web seeds
    'https://my-server.com/files/'
  ]
}, torrent => {
  console.log('Configured web seed connections')
})

Setting Up a Web Seed Server

Requirements

Host the files

Upload your torrent files to a web server with the same directory structure as the torrent.

Enable CORS (for browser clients)

Configure your server to send CORS headers:

Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, HEAD, OPTIONS
Access-Control-Allow-Headers: Range

Support range requests

Enable HTTP range requests for seeking support:

Accept-Ranges: bytes

Nginx Configuration

server {
    listen 80;
    server_name webseed.example.com;
    
    location /files/ {
        alias /var/www/torrents/;
        
        # Enable CORS
        add_header Access-Control-Allow-Origin *;
        add_header Access-Control-Allow-Methods "GET, HEAD, OPTIONS";
        add_header Access-Control-Allow-Headers "Range";
        
        # Support range requests
        add_header Accept-Ranges bytes;
        
        # Handle preflight requests
        if ($request_method = OPTIONS) {
            return 204;
        }
    }
}

Node.js Express Server

import express from 'express'
import cors from 'cors'
import path from 'path'

const app = express()

// Enable CORS for all origins
app.use(cors({
  origin: '*',
  methods: ['GET', 'HEAD', 'OPTIONS'],
  allowedHeaders: ['Range']
}))

// Serve files with range request support
app.use('/files', express.static('/path/to/torrent/files', {
  acceptRanges: true,
  lastModified: true
}))

app.listen(3000, () => {
  console.log('Web seed server listening on http://localhost:3000')
})

Python HTTP Server

from http.server import HTTPServer, SimpleHTTPRequestHandler
import os

class CORSRequestHandler(SimpleHTTPRequestHandler):
    def end_headers(self):
        self.send_header('Access-Control-Allow-Origin', '*')
        self.send_header('Access-Control-Allow-Methods', 'GET, HEAD, OPTIONS')
        self.send_header('Access-Control-Allow-Headers', 'Range')
        self.send_header('Accept-Ranges', 'bytes')
        super().end_headers()
    
    def do_OPTIONS(self):
        self.send_response(204)
        self.end_headers()

os.chdir('/path/to/torrent/files')
server = HTTPServer(('', 8000), CORSRequestHandler)
print('Web seed server running on http://localhost:8000')
server.serve_forever()

Complete Web Seed Example

Create and seed a torrent with web seed support:

import WebTorrent from 'webtorrent'
import express from 'express'
import cors from 'cors'
import path from 'path'

const client = new WebTorrent()

// Set up web seed server
const app = express()
app.use(cors({ origin: '*' }))
app.use('/files', express.static('/path/to/files', { acceptRanges: true }))

const server = app.listen(3000, () => {
  console.log('Web seed server: http://localhost:3000/files/')
  
  // Create torrent with web seed
  client.seed('/path/to/files/video.mp4', {
    name: 'My Video',
    urlList: ['http://localhost:3000/files/'],
    announceList: [
      ['wss://tracker.btorrent.xyz'],
      ['wss://tracker.openwebtorrent.com']
    ]
  }, torrent => {
    console.log('\nTorrent created!')
    console.log('Name:', torrent.name)
    console.log('Info hash:', torrent.infoHash)
    console.log('Web seeds:', torrent.urlList)
    console.log('\nMagnet URI:')
    console.log(torrent.magnetURI)
    console.log('\nSeeding via P2P + web seed...')
    
    // Monitor downloads from web seed
    torrent.on('wire', (wire, addr) => {
      if (wire.type === 'webSeed') {
        console.log('Peer connected via web seed')
      }
    })
  })
})

Browser Considerations

When using web seeds in the browser, the web seed server must have proper CORS headers. Without CORS, browsers will block the requests.

Testing CORS

// Test if web seed has proper CORS
fetch('https://example.com/files/test.mp4', {
  method: 'HEAD',
  headers: { 'Range': 'bytes=0-1' }
})
  .then(response => {
    console.log('CORS headers:', response.headers.get('access-control-allow-origin'))
    console.log('Range support:', response.headers.get('accept-ranges'))
  })
  .catch(err => {
    console.error('CORS error:', err)
  })

Performance Optimization

Load Balancing

Use multiple web seeds for better performance:

client.seed(files, {
  urlList: [
    'https://cdn1.example.com/files/',
    'https://cdn2.example.com/files/',
    'https://cdn3.example.com/files/'
  ],
  maxWebConns: 6  // 2 connections per web seed
})

Geographic Distribution

const webSeeds = [
  'https://us-east.example.com/files/',  // US East Coast
  'https://us-west.example.com/files/',  // US West Coast
  'https://eu.example.com/files/',       // Europe
  'https://asia.example.com/files/'      // Asia
]

client.seed(files, {
  urlList: webSeeds,
  maxWebConns: 8
})

Fallback Strategy

client.add(magnetURI, torrent => {
  // Primary: Try P2P first
  console.log('Trying P2P download...')
  
  // After 30 seconds, add web seed if slow
  setTimeout(() => {
    if (torrent.downloadSpeed < 100000) {  // Less than 100 KB/s
      console.log('Slow P2P, adding web seed')
      torrent.addWebSeed('https://backup.example.com/files/')
    }
  }, 30000)
})

Magnet URI with Web Seeds

Web seeds can be included in magnet URIs using the ws parameter:

const magnetURI = [
  'magnet:?xt=urn:btih:08ada5a7a6183aae1e09d831df6748d566095a10',
  '&dn=Sintel',
  '&ws=https://webtorrent.io/torrents/',
  '&ws=https://backup.example.com/files/',
  '&tr=wss://tracker.btorrent.xyz'
].join('')

client.add(magnetURI, torrent => {
  console.log('Web seeds from magnet:', torrent.urlList)
})

Monitoring Web Seed Usage

Track which sources are being used:

client.add(magnetURI, torrent => {
  const stats = {
    p2p: 0,
    webSeed: 0
  }
  
  torrent.on('wire', (wire, addr) => {
    wire.on('download', bytes => {
      if (wire.type === 'webSeed') {
        stats.webSeed += bytes
      } else {
        stats.p2p += bytes
      }
    })
  })
  
  setInterval(() => {
    console.log('Downloaded from P2P:', (stats.p2p / 1024 / 1024).toFixed(2), 'MB')
    console.log('Downloaded from web seeds:', (stats.webSeed / 1024 / 1024).toFixed(2), 'MB')
    const total = stats.p2p + stats.webSeed
    if (total > 0) {
      console.log('Web seed ratio:', ((stats.webSeed / total) * 100).toFixed(1) + '%')
    }
  }, 5000)
})

Best Practices

Follow these best practices for optimal web seed performance:

Use CDNs: Host web seeds on CDN infrastructure for global performance
Multiple seeds: Provide 2-3 web seeds for redundancy
Keep files synchronized: Ensure web seed content exactly matches torrent
Monitor availability: Check that web seeds remain accessible
Set proper headers: Always configure CORS and range request support
Use HTTPS: Prefer HTTPS for security (required for some browsers)
Rate limiting: Implement rate limiting on web seed servers if needed

Troubleshooting

Web Seeds Not Working

client.add(magnetURI, torrent => {
  // Check if web seeds are configured
  console.log('Web seeds:', torrent.urlList)
  
  // Check if web seeds are enabled
  console.log('Web seeds enabled:', client.enableWebSeeds)
  
  // Monitor for errors
  torrent.on('warning', err => {
    console.warn('Warning:', err.message)
  })
  
  torrent.on('error', err => {
    console.error('Error:', err.message)
  })
})

CORS Issues

If web seeds aren’t working in the browser:

Check browser console for CORS errors
Verify server sends proper CORS headers
Test with curl or browser dev tools
Ensure preflight OPTIONS requests are handled

File Not Found

If web seed returns 404:

Verify file path matches torrent structure exactly
Check URL encoding for special characters
Ensure trailing slash on base URL
Test direct URL access in browser

​What are Web Seeds?

​Adding Web Seeds to Torrents

​Basic Web Seed

​Multiple Web Seeds

​Web Seed URL Format

​Using Torrents with Web Seeds

​Checking Web Seed Status

​Adding Web Seeds to Existing Torrents

​Add When No Peers Available

​Configuring Web Seeds

​Setting Up a Web Seed Server

​Requirements

​Nginx Configuration

​Node.js Express Server

​Python HTTP Server

​Complete Web Seed Example

​Browser Considerations

​Testing CORS

​Performance Optimization

​Load Balancing

​Geographic Distribution

​Fallback Strategy

​Magnet URI with Web Seeds

​Monitoring Web Seed Usage

​Best Practices

​Troubleshooting

​Web Seeds Not Working

​CORS Issues

​File Not Found

What are Web Seeds?

Adding Web Seeds to Torrents

Basic Web Seed

Multiple Web Seeds

Web Seed URL Format

Using Torrents with Web Seeds

Checking Web Seed Status

Adding Web Seeds to Existing Torrents

Add When No Peers Available

Configuring Web Seeds

Setting Up a Web Seed Server

Requirements

Nginx Configuration

Node.js Express Server

Python HTTP Server

Complete Web Seed Example

Browser Considerations

Testing CORS

Performance Optimization

Load Balancing

Geographic Distribution

Fallback Strategy

Magnet URI with Web Seeds

Monitoring Web Seed Usage

Best Practices

Troubleshooting

Web Seeds Not Working

CORS Issues

File Not Found