What is a torrent?

Woman using a Mac
(Image credit: Unsplash / Christin Hume)

Anyone who’s used the Internet knows how to download a file. Simply visit a website, click the link and the download automatically begins. The bits of information that make up that one file, such as an image or eBook are copied from the remote server to your computer. If the download is interrupted for any reason, you may have to start it all over again. 

Torrent files work a little differently. They’re a much faster and better way to download and share files, especially large ones. In fact over 50% of web traffic in the entire world is done via torrents.

How do torrents work? 

Torrents may have a bad reputation as they’re often used by websites that pirate copyrighted media. Still, there’s nothing illegal about them in themselves and as you’ll learn, they can be an extremely efficient way to download and share data.

We already know that traditional downloads work by clicking a link and copying a single file, bit by bit, from a computer on the internet to your home computer. Torrent files - usually identified by the extension .torrent - work with the Bittorrent protocol to help you share and download files via peer-to-peer (P2P).

This means that instead of downloading a file from just one computer, you can download parts of it from multiple computers or ‘peers’ at the same time. This is much faster than traditional downloads.

Let’s say you wanted to download the Adventures of Sherlock Holmes from the Internet Archive. Archive.org offer multiple download methods here. You could download the entire set of audio books as a 565MB ZIP file, but this can be very slow. It can also place a huge burden on the website as multiple users try to download files at once.

Alternatively, you can choose to download a torrent file. This contains all the information about where these books are located. In other words, it contains details of computers of people who have already downloaded these audiobooks, so you can connect to them and do the same. These people are known as seeders.

A matter of protocol 

By itself your torrent file isn’t much use. Yes, it contains the location of other ‘peers’ who have already downloaded the same file, but what good is this if you can’t do the same?

This is where your torrent client comes in. This is a software program capable of reading the torrent file and communicating with seeders in order to download it to your computer.

When you open a .torrent file in the Bittorrent client, it will first look for the ‘tracker’ specified in the file. This is simply the address for a special server which holds a list of users who have a complete copy of the file (in this case some audio books). The Bittorent protocol can break large files into small chunks and help your client connect to and download them from other users.

Once the download is complete, you can also choose to become a ‘seeder’ by leaving your Bittorrent client open to share your download with others.

Torrent treats 

Downloading via bittorrent doesn’t rely on a single computer. As it’s “decentralized”, if one particular computer doesn’t host the files you need any more, you can always get another copy from other ‘seeders’.

The larger the ‘swarm’ - people downloading and sharing the same torrent - the faster the download can be. As you’re copying small bits of information from multiple sources, your download speed isn’t restricted by a single server, as it would be for a regular HTTP download. If a download is interrupted, you can just resume downloading from other peers.

Torrents can also be quite democratic in that if a file turns out not to be as described or is poor quality, fewer people download it. Most bittorrent websites feature rankings for files based on the number of people who’ve successfully downloaded and shared it, allowing you to check which are best.

Torrent tricks 

GIven how efficient the Bittorrent protocol is for sharing large files, it’s hardly surprising that it’s used to share music and videos illegally. Some ISPs monitor users who use torrents or even try to block file-sharing websites sued when sharing big files.

Whilst downloading, your IP address is also visible to everyone else who’s doing the same. If you’re worried about being targeted by hackers, consider using a VPN.

Some Bittorrent clients can also install adware or other forms of malware on your system. Consider having a dedicated machine for downloading internet content and consider installing up to date antivirus software

Just as with traditional downloads, if no one has a copy of a file you need you won’t be able to load it. This means if a site or torrent search engine says a file has zero seeds, downloading the .torrent will have no effect.

Most importantly, using a Bittorrent client means you’ll both be downloading and uploading a lot of data. Check with your network provider to see if there’s a cap on how much data you can transfer monthly and/or there are any extra costs. Many Bittorrent clients allow you to limit the bandwidth for download/upload speeds to make it more manageable.  

The bottom line 

Despite its reputation, downloading files by Bittorrent isn’t in itself illegal. It’s simply a very effective way of transferring data. If you’re considering getting started, make sure to download torrent files only from a reputable source such as the Internet Archive. 

Make sure also to install your Bittorrent client directly from the developer’s website - even versions in mainstream app stores may be unofficial. 

The best way to make sure it’s ad and malware free is to use open source software, where the code is publicly available such as the cross-platform Transmission or qBittorrent clients.  

Nate Drake is a tech journalist specializing in cybersecurity and retro tech. He broke out from his cubicle at Apple 6 years ago and now spends his days sipping Earl Grey tea & writing elegant copy.