How Torrent Downloading Works

A beginners guide to BitTorrent technology

A torrent download in progress.
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BitTorrent networking is the most popular form of modern P2P (peer-to-peer) file sharing. Since 2006, BitTorrent sharing has been the primary means for users to trade software, music, movies, and digital books online. To download torrents, you need a special P2P file sharing client such as BitTorrent Web.

BitTorrent refers to both the name of the technology and the original client created for exchanging torrents. The original BitTorrent client is now called BitTorrent Classic.

What Are BitTorrents?

BitTorrents (also known as torrents) work by downloading small bits of files from many different web sources at the same time. A few torrent search providers charge users a fee for their service, but torrent clients and torrents themselves are free to download.

While the use of BitTorrent clients is legal, downloading and uploading songs, movies, or TV shows is a violation of copyright law in many jurisdictions.

Torrents Vs. Traditional File Sharing

BitTorrent clients are different from other file-sharing networks like Kazaa and Shareaza in a few ways:

  • Torrent networking doesn't require a subscription or account with any service.
  • Torrents filter out corrupted and dummy files, ensuring that downloads contain only what they claim to contain.
  • Torrent clients encourage users to share ("seed") their complete files, while simultaneously penalizing users who don't share ("leechers").
  • Torrents can achieve download speeds over 1.5 megabits per second.
  • Torrent code is open-source and ad-free, so no single person profits from file sharing.

How BitTorrent Sharing Works

Torrent sharing utilizes techniques called "swarming" and "tracking," which allows users to download many small bits from many different sources at once.

  • Swarming means splitting large files into hundreds of smaller "bits" and then sharing those bits across a "swarm" of dozens of linked users.
  • Tracking occurs when specific servers help swarm users find each other.

Swarm members use special Torrent client software to upload, download, and reconstruct the many file bits into complete usable files. Special .torrent text files act as pointers during this whole process, helping users find other users to swarm with, and enforcing quality control on all shared files. Because this format compensates for bottleneck points, it is actually faster than downloading a large file from a single source.

While older file sharing programs like Kazaa rely on publisher servers to dish out files, torrent users do all the file serving. Torrent users voluntarily upload their file bits to their swarm without going through a centralized service. Download speed is controlled by torrent tracking servers, which monitor all swarm users. If you share, tracker servers will reward you by increasing your allotted swarm bandwidth (sometimes up to 1500 kilobits per second). If you leech and limit your upload sharing, tracking servers will choke your download speeds, sometimes to as slow as 1 kilobit per second.

What You Need to Download Torrents

BitTorrent swarming requires five major ingredients:

  • A BitTorrent client
  • A tracker server
  • A .torrent text file that points to the movie/song/file you want to download
  • A torrent search engine that helps you find .torrent text files
  • A specially-configured Internet connection with port 6881 opened on the server/router to allow torrent file trading.

If you use a hardware router or software firewall, you may need to set up your router/firewall to trust BitTorrent data.

How to Download BitTorrents

The torrent download process goes likes this:

  1. Use a torrent search engine, such as RARGB, to find .torrent text files.

    Use a torrent search engine, such as RARGB, to find .torrent text files.
  2. Download the desired .torrent file to your computer.

    Most search engines will return multiple files of the same movie/song/etc. Note the size and quality of each file before making a selection to pick the best version.

    Download the desired .torrent file to your computer.
  3. Open the .torrent file in your torrent client of choice.

    Open the .torrent file with your torrent client of choice.
  4. The torrent client software will automatically communicate with a tracker server and scour the internet for swarms of other users who have the same exact .torrent file. Once seeders have been found, the client software then begins the transfer.

    A torrent is being downloaded in the BitTorrent Web client.

It can take hours or even days to download large files such as movies. Fortunately, if you need to turn off your computer during this time, you can resume downloading from where you left off.

Once the transfer is complete, leave your torrent client software running to share your completed files with other users and increase your upload/download ratio.

Consider purchasing an extra hard drive to store the files you download.