What is a magnetic link and how do you use one?

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When you last downloaded a torrent file, you might have been offered a magnetic link as an alternative. Magnetic links are very different from torrent files and offer certain benefits that all torrent users should be aware of.

How traditional torrent files work

We won’t go into all the details of how BitTorrent works here. But magnetic links are an alternative to traditional torrent files. Here’s how traditional torrent files work:

  • Torrent files do not contain any data of the files you want to download.
  • The file contains a list of torrent trackers (if any) that coordinate all the peers participating in the torrent.
  • It contains information about shared files, such as their names, sizes, and information needed to perform integrity checks on the data.

Torrent files can also contain extended information, such as a Distributed Hash Table (DHA) that allows each peer to act as part of a decentralized tracking network. DHA is an important concept to remember when discussing magnetic bonds.

What is a magnetic link?

In essence, a magnetic link is simply a string of text. However, there is a lot of information in this channel!

A magnetic link contains a unique identifier, various parameters depending on the exact nature of the torrent and, most importantly, a cryptographic hash of the torrent files.

A cryptographic hash is a mathematical algorithm applied to data that results in a unique short string that represents that data. This is useful for torrents because you can hash two torrents and if they point to the exact same files they will have identical hashes.

So, in order for your torrent client to know who else is part of a given torrent, they just need to compare the hash in the magnetic link to the hashes of the torrents that are being shared. Filtering only those with matching hashes quickly reconstructs the peer swarm on the network. This is the same method used by the distributed hash table found in “no tracker” torrents. These are torrents that do not use a central server to coordinate peers and keep track of peers.

A magnetic link only removes this essential information and removes the rest of the torrent file, since the vast majority of torrent participants do not need this information.

The advantages of magnetic links

Magnetic links are becoming the norm and there are benefits for torrent providers and torrent users alike in leading this change.

The first big advantage of magnetic links is that they are links, not files. It may seem like an irrelevant distinction, but the files need to be hosted and uploaded. Magnetic links can be part of a web page just like any hyperlink. Users don’t have to go through the extra step of downloading and opening a file, and vendors don’t have to worry about a file hosting solution.

All files downloaded from the internet come with inherent risk malware, which does not apply to magnet links. Magnetic links are also much easier to share. You can email them, send them as a text message, or through any popular messaging app.

Magnetic links also have a big advantage over using torrent trackers. A torrent based on a magnetic link hash is incredibly robust. As long as only one planter remains online, anyone else with the magnetic link can find it. Even though none of the original contributors are there. As long as the hash can be re-created from the torrent files, the existing magnet links will continue to work.

How to use a magnetic link

Using a magnetic link is as easy as clicking on a link on a web page. If you have installed a BitTorrent client that supports magnet links, your web browser should prompt you to open the magnet link in your torrent client. You can also copy and paste the link into BitTorrent clients which have an address bar for this purpose.

Once you’ve done that, everything else should happen automatically.

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